From temblor: “Quake Connectivity: 3 January 2019 M=5.1 Japan shock was promoted by the April 2016 M=7.0 Kumamoto earthquake”

From temblor

January 7, 2019
By Shinji Toda, Ph.D. (IRIDeS, Tohoku University)
Ross S. Stein, Ph.D. (Temblor, Inc.)

Was the small but strong shock in southern Japan a random event?

In the late evening on January 3, a M=5.1 earthquake caused strong local ground shaking (JMA Intensity 6-, equivalent to MMI Intensity IX-X) in Nagomi-machi, ~25 km north of Kumamoto City (Fig. 1). Although the quake brought only light damage to the town, it stopped the Shinkansen ‘bullet trains’ and highway services for an emergency check-up during Japan’s well-traveled New Year holiday.

Figure 1. JMA intensity distribution of the January 3 M=5.1 earthquake. At the epicenter (X), the shaking reached JMA 6-.

Japan’s Headquarters for Earthquake Research Promotion (HERP) declares the M=5.1 to be unrelated to the 2016 M=7.0 shock. We beg to differ.

This quake recalls the devastating 2016 Mw=7.0 (Mjma=7.3) Kumamoto earthquake that killed 50 people and destroyed thousands of houses (Hashimoto et al., 2017). Immediately after the M=5.1 shock, HERP (2019) announced that there is no causal relation between the 3 Jan 2019 shock and the 15 April 2016 Kumamoto earthquake. In contrast, we contend that the M=5.1 is instead part of the long-lasting and remarkably widespread aftershock sequence of the M=7.0 Kumamoto earthquake.

Figure 2. (Left panel) Coulomb stress imparted by the 2016 Kumamoto earthquake sequence to the surrounding crust as a result of the combined Mw=6.0 and Mw=7.0 shocks. This figure was originally posted in a Temblor blog (Stein and Toda, 2016). Regions in which strike-slip faults are brought closer to failure are red (‘stress trigger zones’); regions now inhibited from failure are blue (‘stress shadows’). Aftershocks during first three months (translucent green dots) generally lie in regions brought closer to failure. The January 3 event (yellow star) is located in one of the stress trigger zones.

(Right panel) Seismicity rate change between before (2009/01/01-2016/04/14) and after (2016/04/14-2019/01/02) the 2016 Kumamoto earthquake sequence. Red areas ‘turned on’ after the 2016 mainshock; blue areas ‘shut down.’

The M=5.1 shock struck in a previously published Coulomb ‘stress trigger zone’

In the web article of the IRIDeS Tohoku University released immediately after the 2016 shock (IRIDeS, 2016) and our blog article posted on September 2, 2016 (Stein and Toda, 2016), we emphasized the effect of Coulomb stress transfer to nearby regions (warmer color regions in Fig. 2 left panel), and mentioned the initial aftershocks mostly occurred in the regions where we calculated that the Coulomb stress increased. The Jan 3, 2019 M=5.1 shock indeed occurred in one of the stress increased lobes (yellow star in Fig. 2). This lobe experienced an increase in seismicity after the Kumamoto mainshock (Box A in Fig. 3 below).

Figure 3. Epicenters of all earthquakes shallower than 20 km during the period of 2015-2018 (JMA catalog). Although there are several dense clusters that have nothing to do with the Kumamoto earthquake, we nevertheless see that the aftershock zone is extends up to five rupture lengths from the fault (thick black line). The three boxes are where we examined the seismicity over time in Figure 4.

The quake rate doubled in the stress trigger zone of the 2016 Mw=7.0 quake, and dropped by a factor of 5 in its stress shadow.

Given that Japan is such an earthquake-prone country, one could argue that it was simply a random accident that the M=5.1 quake struck in the stress trigger zone. To address this possibility, we first examined the change in earthquake occurrence rate (‘seismicity rate change’) before and after the 2016 Kumamoto earthquake (Fig. 2 right panel). A visual comparison of our Coulomb calculation (Fig. 2 left panel) with seismicity rate change (Fig. 2 right panel) shows they match reasonably well. The epicenter of the 3 January 2019 event is in the red spot on both maps. Furthermore, regions north and south of the 2016 rupture zone, in which the faults were inhibited from failure by the stress changes, indeed show a seismicity decrease.

To make sure that the local seismicity responded to the Kumamoto earthquake and not some other event at roughly the same time, we have chosen three sub-regions (boxes in Fig. 3) and looked at their seismicity time series (Fig. 4). In box A, the number of shocks, most of which are very small, was ~600 a year before the 2016 mainshock. But it has risen by over 2, to ~1500 per year since the mainshock. Thus, the M=5.1 event occurred in the zone of sustained higher rate of seismicity associated with the 2016 Kumamoto earthquake. A similar continuous and long-lasting seismicity increase also occurred in box C (northern Miyazaki Prefecture) where Coulomb stress was also imparted by the mainshock. The opposite response is observed in box B, where Coulomb stress was calculated to have decreased. There, the seismicity plummeted to 1/5 of the pre-Kumamoto level.

Figure 4. Seismic time series in the particular sub-regions, A, B, and C, corresponding to the boxes in Fig. 2 left panel and Fig. 3. The blue line indicates cumulative number of earthquakes since 2015 (with the corresponding blue scale at left), whereas the green stems identify each earthquake time and magnitude (green scale at right). What’s clear is that in all cases, the seismicity rates changed roughly at the time of the 2016 Kumamoto mainshock, and in the manner forecast by the Coulomb stress changes.

There is a caveat that the Japan Meteorological Agency (JMA) has changed their earthquake determination algorithm after April 2016. However, it should have been homogeneously implemented in Kyushu. Since we confirmed the regional-dependent seismic behaviors in Fig. 4, we do not think the increased seismicity in the box A in Fig. 4 is an artifact. We also note that the rate of shallow M≥5 earthquakes under inland Japan (378,000 km2) is roughly about 10 a year. It enables us to say the probability to have one M≥5 quake in the box A (1168 km2) per year is ~3%, and so it is rare enough to make an accidental or coincidental occurrence unlikely.

The long-lasting and far-reaching impact of stress transfer on seismic hazard.

A key lesson learned from this M=5.1 quake is the effect of stress disturbance due to the three-year-old M=7 event continues over a large area in central Kyushu. And even though the size of the January 3 quake is much smaller than the M=7.0, it can nevertheless cause serious damage. Further, aftershocks do not get smaller with time after a mainshock; instead they only get more spaced out in time. So, a larger shock could still strike. The most likely place for such an event is unfortunately the highly-populated Kumamoto city, because there the stress imparted by the 2016 mainshock was greater than anywhere else.

References

Manabu Hashimoto, Martha Savage, Takuya Nishimura, Haruo Horikawa and Hiroyuki Tsutsumi (2017), Special issue “2016 Kumamoto earthquake sequence and its impact on earthquake science and hazard assessment” Earth, Planets and Space, 69-98, https://earth-planets-space.springeropen.com/articles/10.1186/s40623-017-0682-7

Headquarters for Earthquake Research Promotion (2019), https://www.static.jishin.go.jp/resource/monthly/2019/20190103_kumamoto.pdf

IRIDeS (International Research Institute of Disaster Science) (2016), http://irides.tohoku.ac.jp/event/2016kumamotoeq_science.html

Ross S. Stein and Volkan Sevilgen (2016), The Tail that Wagged the Dog: M=7.0 Kumamoto, Japan shock promoted by M=6.1 quake that struck 28 hr beforehand http://temblor.net/earthquake-insights/japan-542/

Ross S. Stein and Shinji Toda (2016), How a M=6 earthquake triggered a deadly M=7 in Japan, Temblor http://temblor.net/earthquake-insights/how-a-m6-earthquake-triggered-a-deadly-m7-in-japan-1304/

See the full article here .

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Earthquake Alert

Earthquake Alert

Earthquake Network project

Earthquake Network is a research project which aims at developing and maintaining a crowdsourced smartphone-based earthquake warning system at a global level. Smartphones made available by the population are used to detect the earthquake waves using the on-board accelerometers. When an earthquake is detected, an earthquake warning is issued in order to alert the population not yet reached by the damaging waves of the earthquake.

The project started on January 1, 2013 with the release of the homonymous Android application Earthquake Network. The author of the research project and developer of the smartphone application is Francesco Finazzi of the University of Bergamo, Italy.

Get the app in the Google Play store.

Smartphone network spatial distribution (green and red dots) on December 4, 2015

Meet The Quake-Catcher Network

Quake-Catcher Network

The Quake-Catcher Network is a collaborative initiative for developing the world’s largest, low-cost strong-motion seismic network by utilizing sensors in and attached to internet-connected computers. With your help, the Quake-Catcher Network can provide better understanding of earthquakes, give early warning to schools, emergency response systems, and others. The Quake-Catcher Network also provides educational software designed to help teach about earthquakes and earthquake hazards.

After almost eight years at Stanford, and a year at CalTech, the QCN project is moving to the University of Southern California Dept. of Earth Sciences. QCN will be sponsored by the Incorporated Research Institutions for Seismology (IRIS) and the Southern California Earthquake Center (SCEC).

The Quake-Catcher Network is a distributed computing network that links volunteer hosted computers into a real-time motion sensing network. QCN is one of many scientific computing projects that runs on the world-renowned distributed computing platform Berkeley Open Infrastructure for Network Computing (BOINC).

The volunteer computers monitor vibrational sensors called MEMS accelerometers, and digitally transmit “triggers” to QCN’s servers whenever strong new motions are observed. QCN’s servers sift through these signals, and determine which ones represent earthquakes, and which ones represent cultural noise (like doors slamming, or trucks driving by).

There are two categories of sensors used by QCN: 1) internal mobile device sensors, and 2) external USB sensors.

Mobile Devices: MEMS sensors are often included in laptops, games, cell phones, and other electronic devices for hardware protection, navigation, and game control. When these devices are still and connected to QCN, QCN software monitors the internal accelerometer for strong new shaking. Unfortunately, these devices are rarely secured to the floor, so they may bounce around when a large earthquake occurs. While this is less than ideal for characterizing the regional ground shaking, many such sensors can still provide useful information about earthquake locations and magnitudes.

USB Sensors: MEMS sensors can be mounted to the floor and connected to a desktop computer via a USB cable. These sensors have several advantages over mobile device sensors. 1) By mounting them to the floor, they measure more reliable shaking than mobile devices. 2) These sensors typically have lower noise and better resolution of 3D motion. 3) Desktops are often left on and do not move. 4) The USB sensor is physically removed from the game, phone, or laptop, so human interaction with the device doesn’t reduce the sensors’ performance. 5) USB sensors can be aligned to North, so we know what direction the horizontal “X” and “Y” axes correspond to.

If you are a science teacher at a K-12 school, please apply for a free USB sensor and accompanying QCN software. QCN has been able to purchase sensors to donate to schools in need. If you are interested in donating to the program or requesting a sensor, click here.

BOINC is a leader in the field(s) of Distributed Computing, Grid Computing and Citizen Cyberscience.BOINC is more properly the Berkeley Open Infrastructure for Network Computing, developed at UC Berkeley.

Earthquake safety is a responsibility shared by billions worldwide. The Quake-Catcher Network (QCN) provides software so that individuals can join together to improve earthquake monitoring, earthquake awareness, and the science of earthquakes. The Quake-Catcher Network (QCN) links existing networked laptops and desktops in hopes to form the worlds largest strong-motion seismic network.

Below, the QCN Quake Catcher Network map

ShakeAlert: An Earthquake Early Warning System for the West Coast of the United States

The U. S. Geological Survey (USGS) along with a coalition of State and university partners is developing and testing an earthquake early warning (EEW) system called ShakeAlert for the west coast of the United States. Long term funding must be secured before the system can begin sending general public notifications, however, some limited pilot projects are active and more are being developed. The USGS has set the goal of beginning limited public notifications in 2018.

Watch a video describing how ShakeAlert works in English or Spanish.

The primary project partners include:

United States Geological Survey
California Governor’s Office of Emergency Services (CalOES)
California Geological Survey
California Institute of Technology
University of California Berkeley
University of Washington
University of Oregon
Gordon and Betty Moore Foundation

The Earthquake Threat

Earthquakes pose a national challenge because more than 143 million Americans live in areas of significant seismic risk across 39 states. Most of our Nation’s earthquake risk is concentrated on the West Coast of the United States. The Federal Emergency Management Agency (FEMA) has estimated the average annualized loss from earthquakes, nationwide, to be $5.3 billion, with 77 percent of that figure ($4.1 billion) coming from California, Washington, and Oregon, and 66 percent ($3.5 billion) from California alone. In the next 30 years, California has a 99.7 percent chance of a magnitude 6.7 or larger earthquake and the Pacific Northwest has a 10 percent chance of a magnitude 8 to 9 megathrust earthquake on the Cascadia subduction zone.

Part of the Solution

Today, the technology exists to detect earthquakes, so quickly, that an alert can reach some areas before strong shaking arrives. The purpose of the ShakeAlert system is to identify and characterize an earthquake a few seconds after it begins, calculate the likely intensity of ground shaking that will result, and deliver warnings to people and infrastructure in harm’s way. This can be done by detecting the first energy to radiate from an earthquake, the P-wave energy, which rarely causes damage. Using P-wave information, we first estimate the location and the magnitude of the earthquake. Then, the anticipated ground shaking across the region to be affected is estimated and a warning is provided to local populations. The method can provide warning before the S-wave arrives, bringing the strong shaking that usually causes most of the damage.

Studies of earthquake early warning methods in California have shown that the warning time would range from a few seconds to a few tens of seconds. ShakeAlert can give enough time to slow trains and taxiing planes, to prevent cars from entering bridges and tunnels, to move away from dangerous machines or chemicals in work environments and to take cover under a desk, or to automatically shut down and isolate industrial systems. Taking such actions before shaking starts can reduce damage and casualties during an earthquake. It can also prevent cascading failures in the aftermath of an event. For example, isolating utilities before shaking starts can reduce the number of fire initiations.

System Goal

The USGS will issue public warnings of potentially damaging earthquakes and provide warning parameter data to government agencies and private users on a region-by-region basis, as soon as the ShakeAlert system, its products, and its parametric data meet minimum quality and reliability standards in those geographic regions. The USGS has set the goal of beginning limited public notifications in 2018. Product availability will expand geographically via ANSS regional seismic networks, such that ShakeAlert products and warnings become available for all regions with dense seismic instrumentation.

Current Status

The West Coast ShakeAlert system is being developed by expanding and upgrading the infrastructure of regional seismic networks that are part of the Advanced National Seismic System (ANSS); the California Integrated Seismic Network (CISN) is made up of the Southern California Seismic Network, SCSN) and the Northern California Seismic System, NCSS and the Pacific Northwest Seismic Network (PNSN). This enables the USGS and ANSS to leverage their substantial investment in sensor networks, data telemetry systems, data processing centers, and software for earthquake monitoring activities residing in these network centers. The ShakeAlert system has been sending live alerts to “beta” users in California since January of 2012 and in the Pacific Northwest since February of 2015.

In February of 2016 the USGS, along with its partners, rolled-out the next-generation ShakeAlert early warning test system in California joined by Oregon and Washington in April 2017. This West Coast-wide “production prototype” has been designed for redundant, reliable operations. The system includes geographically distributed servers, and allows for automatic fail-over if connection is lost.

This next-generation system will not yet support public warnings but does allow selected early adopters to develop and deploy pilot implementations that take protective actions triggered by the ShakeAlert notifications in areas with sufficient sensor coverage.

Authorities

The USGS will develop and operate the ShakeAlert system, and issue public notifications under collaborative authorities with FEMA, as part of the National Earthquake Hazard Reduction Program, as enacted by the Earthquake Hazards Reduction Act of 1977, 42 U.S.C. §§ 7704 SEC. 2.

For More Information

Robert de Groot, ShakeAlert National Coordinator for Communication, Education, and Outreach
rdegroot@usgs.gov
626-583-7225

Learn more about EEW Research

ShakeAlert Fact Sheet

ShakeAlert Implementation Plan

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From CSIROscope: “Did a hotspot break up your relationship?”

From CSIROscope

7 January 2019
Sophie Schmidt

Women make up 85% of scientists on this voyage of RV Investigator, which is being led by the University of Tasmania.

RV Investigator Australia

We’re back out on the waves on board RV Investigator serving up live science plucked fresh from the high seas – and what a voyage it’s been! Since departing Hobart just after Christmas, we’ve been busy sailing for science – not in pursuit of freaky abyssal fish, nor whale watching or shipwrecks – this time we’ve set out for the love of rocks.

Yep, you read it correctly. The Chief Scientist, Dr Jo Whittaker from the University of Tasmania is leading a team of geologists on a two-week voyage to undertake research into one of those huge, soul-searching kind of break ups. Think less Ariana and Pete (hello, millennials, are you reading CSIROscope?) and more Australia and Antarctica.

We’re hoping that we might get the closure we need by investigating an area hundreds of kilometres off the coast of Tasmania brimming with seamounts (underwater volcanic mountains).

All of this drama went down like, 35 million years ago, so we should really be over it by now, but according to Jo, it’s vital that we understand what happened in Antarctica’s past in order to predict its future.

Jill, CSIRO summer scholar student (right) has been busy mapping seamounts as part of our Geophysical Survey and Mapping (GSM) team.

Smoke in the water

Seamounts are caused by mantle plumes – basically, the homewreckers of the lithosphere (the Earth’s crust and upper mantle). Mantle plumes are an up-welling of extra-hot molten rock (magma) from the mantle below and they can seriously mess stuff up. They can cause the Earth’s crust to weaken and rise up through the sea floor, creating big structures such as seamounts and large underwater plateaus, like the Kerguelen Plateau in the Southern Ocean.

While a mantle plume more or less stays put over time, tectonic plates can continue to drift over it, resulting in seamounts sprouting up in chains across the seafloor. A mantle plume can also cause the Earth’s surface to be uplifted.

Jo thinks that if we can determine the age and the order in which the seamounts we are studying sprouted as a result of the Balleny mantle plume, we’ll get a better understanding of the role this plume played in this epic break-up.

“Antarctica underwent a dramatic change 34 million years ago going from Tasmanian rainforests to a glaciated state,” says Jo.

“Around the same time, it’s thought that the Tasman Gateway, separating Antarctica from Tasmania, opened up.”

“This research is all about determining whether the mantle plume played a role in opening the Gateway.”

Voyage Chief Scientist Jo Whittaker inspects the contents of the latest geological treasure haul.

Rockin’ n rollin’

Faced with the prospect of a dry ship on New Years’ Eve and oscillating bouts of sea sickness – compounded by my baseline understanding of geology (which has marginally improved), it’s been a seamount-shaped learning curve catching up on the science above and below decks.

RV Investigator operates 24 hours a day (eye-masks issued on board say “good science doesn’t sleep but good scientists do”) and being on board this world-class research vessel feels like living inside a big, heaving, cooperative sea creature, fuelled by the enthusiasm and smarts of the crew, scientists and support staff on board.

(In case you can’t tell) Tom, PhD student from University of Tasmania is excited to find some fresh basalt, because it will clue us in to the age of one of the seamounts.

Much to one geologist’s delight, we occasionally dig up sediment. Popping this under the microscope can reveal a catalogue of million-year-old microfossils including the remnants of coral and plankton which can be dated.

Everyone is connected on board by some advanced and not so advanced technology. It’s not unusual to wake up to a message from a scientist at 2am posting a photo from another ‘gorgeous dredge’ or to find napkins passionately scribbled with geological diagrams lying around the ship’s galley.

RV Investigator has advanced multibeam systems that can map to full ocean depth.

Navigating the unknown is, of course, made much easier with detailed maps and our geospatial mapping team has been constantly collecting seafloor data in rotating 12-hour shifts. The maps are used to decide which part of the seamount we’d like to sample. The ship’s winch is then used to lower a dredge down to thousands of metres below the ocean surface to sample along the top of the seamount.

Enough about us, though – let’s jump into a quick recap of why we’re here.

Australia and Antarctica – a lava story
When things were good, they were really good

We don’t know how long Tasmania and Antarctica shacked up together before separating around 100 million years ago but their relationship goes back at least 500 million years (New Zealand came along for the ride too #itscomplicated).

But their issues only became bigger and bigger

At some point, maybe around 80 million years ago, tension rose to the surface. The Balleny mantle plume, a hotspot, appeared on the scene and fired up seamount after seamount in progressive chains. After being so close for so long, Antarctica and Tasmania started to drift apart.

They decided their problems were just too big to solve

At first, Tasmania started to back off slowly, at a rate of a few millimetres or so per year.

Then, around 35 million years ago, rapid uplift of the crust saw Tasmania start zipping north at around 7 centimetres per year. It was time for Tasmania to move on, and leave the hotspot and Antarctica behind.

Antarctica turned pretty frosty post-split

Around 34 million years ago Antarctica became increasingly cold – icy, if you will – and the happy memories of the flora and fauna it once shared with Tasmania became a thing of the past. Perhaps Tasmania still carried a flame as it moved north – after all, its rocks, landforms, soils and vegetation are all by-products from a long-term relationship with Antarctica.

As continental drift accelerated, the sea floor widened enough to form a gateway (opening) for colder waters to start circulating around Antarctica. We call this the Antarctic Circumpolar Current (ACC), which thermally isolates Antarctica and helps keeps it cold.

It’s possible that the uplift of the seafloor could have led to the opening of the Tasman Gateway – and the related onset of the ACC. Determining how and when the seamounts formed in this region will help us better understand the evolution of the ACC.

Emily is an Australian teacher on board under our Educator on Board Program. When she’s not assisting scientists with preparing samples, she’s coming up with new geological slants for the school curriculum.

Get your rocks off (the dredge and into the lab)

Even though things have cooled off, we still have some lingering questions to be answered. Did continental drift alone cause the Tasman Gateway to open, leading to Antarctica’s progressively cold state? How drastically did the Balleny mantle plume affect the seafloor over time?

Out here, Jo’s looking for those answers in the rock samples, which she describes as ‘geological time capsules’– they’ll be dated and analysed back at the lab.

“All of the data we’re collecting will be used to train better models used to predict what will happen to Antarctica’s future coastline and the melting of its ice sheets.”

“We’ll understand how the Tasman gateway opened – and whether or not the mantle plume played a major role in the glaciation of Antarctica.”

Scientists are seeking to join the dots to better understand this chain of seamounts that stretches across the Tasman Sea.

See the full article here .

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SKA/ASKAP radio telescope at the Murchison Radio-astronomy Observatory (MRO) in Mid West region of Western Australia

So what can we expect these new radio projects to discover? We have no idea, but history tells us that they are almost certain to deliver some major surprises.

Making these new discoveries may not be so simple. Gone are the days when astronomers could just notice something odd as they browse their tables and graphs.

Nowadays, astronomers are more likely to be distilling their answers from carefully-posed queries to databases containing petabytes of data. Human brains are just not up to the job of making unexpected discoveries in these circumstances, and instead we will need to develop “learning machines” to help us discover the unexpected.

With the right tools and careful insight, who knows what we might find.

CSIRO, the Commonwealth Scientific and Industrial Research Organisation, is Australia’s national science agency and one of the largest and most diverse research agencies in the world.

From Eos: “Regional Metamorphism Occurs Before Continents Collide”

From AGU

From Eos

Glencoe in the Highlands of Scotland, where geologist George Barrow first recognized Barrovian geological regional metamorphism. New research suggests that the source for the high temperatures indicated by the metamorphism occurred before—not as a result of—continental collision. iStock.com/iweta0077

1.3.19
Terri Cook

While studying rocks in the Scottish Highlands in the late 1800s, George Barrow mapped a sequence of mineral zones representing increasingly higher grades of metamorphism at inferred increasing temperature and depth in Earth. Now known to represent the most common type of regional metamorphism, the Barrovian sequence has been widely documented in areas that experienced the elevated temperatures associated with continental collision and other tectonic deformation.

Barrovian metamorphism is distinguished by a high vertical temperature gradient that, when extrapolated, yields temperatures of 800°C to 850°C at the base of 35-kilometer-thick crust—nearly double that of stable continental areas. Previous research has found a number of mechanisms to explain these high temperatures, including frictional heating, magmatism, and underthrusting of crust containing abundant radioactive heat generation. However, none of these mechanisms are entirely consistent with field evidence showing that some regional metamorphism occurs prior to or during deformation—or the fact that only lithosphere that is already warm is weak enough to be deformed by the forces generated at plate boundaries.

Here Hyndman [Geochemistry, Geophysics, Geosystems] proposes a new theory to overcome the problems of these previous explanations. Namely, the high temperatures responsible for Barrovian metamorphism are not caused by heat generated during and after deformation; instead, these temperatures predate continental collision and other tectonic deformation.

According to the author, the high temperatures have their origin in precollision hot back arcs—broad areas, up to 1,000 kilometers wide, found landward of the subduction zones that must occur on at least one side as continents converge and oceans close. This idea is based on recent observations that most modern subduction zones have uniformly hot back arcs with thin lithospheres and vertical temperature gradients that are remarkably consistent with Barrovian metamorphism. Most collision deformation and regional metamorphism around the world are concentrated in former hot, weak back arcs, which had Barrovian temperature gradients prior to ocean closure and collision.

By concluding that regional metamorphism and deformation can result from back-arc crust that was already heated to high temperatures prior to deformation, this paper offers an innovative vision of the thermal structure of many ancient and modern collision zones.

See the full article here .

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Eos is the leading source for trustworthy news and perspectives about the Earth and space sciences and their impact. Its namesake is Eos, the Greek goddess of the dawn, who represents the light shed on understanding our planet and its environment in space by the Earth and space sciences.

From The New York Times: “The Earth’s Shell Has Cracked, and We’re Drifting on the Pieces”

From The New York Times

Dec. 18, 2018
Natalie Angier

Plate tectonics helped make our planet stable and habitable. But the slow shifting of continents is still a mysterious process.

The San Andreas fault in the Carrizo Plain in California. The fault line forms the boundary between the Pacific and the North American plates. Credit Peter Menzel/Science Source

The theory of plate tectonics is one of the great scientific advances of our age, right up there with Darwin’s theory of evolution and Einstein’s theory of relativity.

The idea that Earth’s outer shell is broken up into giant puzzle pieces, or plates, all gliding atop a kind of conveyor belt of hot, weak rock — here rising up from the underlying mantle, there plunging back into it — explains much about the structure and behavior of our home planet: the mountains and ocean canyons, the earthquakes and volcanoes, the very composition of the air we breathe.

Yet success is no guarantee against a midlife crisis, and so it is that half a century after the basic mechanisms of plate tectonics were first elucidated, geologists are confronting surprising gaps in their understanding of a concept that is truly the bedrock of their profession.

They are sparring over when, exactly, the whole movable plate system began. Is it nearly as ancient as the planet itself — that is, roughly 4.5 billion years old — or a youthful one billion years, or somewhere in between?

They are asking what caused the shell to crack apart in the first place, and how the industrious recycling of Earth’s crust began.

They are comparing Earth with its sister planet, Venus. The two worlds are roughly the same size and built of similar rocky material, yet Earth has plate tectonics and Venus does not. Scientists want to know why.

“In the 1960s and 70s, when people came up with the notion of plate tectonics, they didn’t think about what it was like in the distant past,” said Jun Korenaga, a geophysicist at Yale University.

“People were so busy trying to prove plate tectonics by looking at the present situation, or were caught up applying the concept to problems in their own field. The origin issue is a much more recent debate.”

Researchers also are exploring the link between plate tectonics and the evolution of complex life. Fortuitously timed continental collisions and mountain smackdowns may well have supplied crucial nutrients at key moments of biological inventiveness, like the legendary Cambrian explosion of 500 million years ago, when the ancestors of modern life-forms appeared.

“The connection between deep Earth processes and Earth surface biology hasn’t been thought about too clearly in the past, but that’s changing fast,” said Aubrey Zerkle, a geochemist at the University of St. Andrews in Scotland.

It’s increasingly obvious that “you need plate tectonics to sustain life,” Dr. Zerkle added. “If there wasn’t a way of recycling material between mantle and crust, all these elements that are crucial to life, like carbon, nitrogen, phosphorus and oxygen, would get tied up in rocks and stay there.”

The origin and implications of plate tectonics were the subject of a recent meeting and themed issue of Philosophical Transactions of the Royal Society.

Researchers said that pinning down when and how Earth’s vivid geological machinations arose will do more than flesh out our understanding of our home base. The answers could well guide our search for life and habitable planets beyond the solar system.

Robert Stern, a geoscientist at the University of Texas at Dallas, argues that if we’re looking for another planet to colonize, we want to avoid ones with signs of plate tectonic activity. Those are the places where life is likely to have evolved beyond the “single cell or worm stage, and we don’t want to fight another technological civilization for their planet.”

“A relatively benign way for the Earth to lose heat”

Mount Singabung erupting in Indonesia in October 2014. Plate tectonics “allows Earth to maintain a stabler and more benign environment overall,” explained one scientist. Credit Dedy Sahputra/European Pressphoto Agency

The idea that continents are not fixed but rather peregrinate around the globe dates back several centuries, when mapmakers began noticing the complementarity of various land masses — for example, the way the northeast bulge of South America looks as though it could fit snugly in the cupped palm of the southwest coast of Africa.

But it wasn’t until the mid-twentieth century that the generic notion of “continental drift” was transformed into a full-bodied theory, complete with evidence of a subterranean engine driving these continental odysseys.

Geologists determined that Earth’s outer layer is broken into eight or nine large segments and five or six smaller ones, a mix of relatively thin, dense oceanic plates riding low and thicker, lighter continental plates bobbing high.

At large fissures on the ocean floor, melting rock from the underlying mantle rises up, adding to the oceanic plates. At other fracture points in the crust, oceanic plates are diving back inside, or subducting, their mass devoured in the mantle’s hot belly.

The high-riding continental plates are likewise jostled by the magmatic activity below, skating around at an average pace of one or two inches a year, sometimes crashing together to form, say, the Himalayan mountain chain, or pulling apart at Africa’s Great Rift Valley.

All this convective bubbling up and recycling between crust and mantle, this creative destruction and reconstruction of parts — “tectonic” comes from the Greek word for build — is Earth’s way of following the second law of thermodynamics. The movement shakes off into the frigidity of space the vast internal heat that the planet has stored since its violent formation.

And while shifting, crumbling plates may seem inherently unreliable, a poor foundation on which to raise a family, the end result is a surprising degree of stability. “Plate tectonics is a relatively benign way for Earth to lose heat,” said Peter Cawood, an Earth scientist at Monash University in Australia.

“You get what are catastrophic events in localized areas, in earthquakes and tsunamis,” he added. “But the mechanism allows Earth to maintain a stabler and more benign environment overall.”

Sulfuric gas in the Afar Triple Junction in Ethiopia, at the top of the Great Rift Valley. Three tectonic plates meet at this spot: the Arabian plate and two African plates, Nubian and Somali. Credit Massimo Rumi/Barcroft Media, via Getty Images

Unfortunately for geologists, the very nature of plate tectonics obscures its biography. Oceanic crust, where the telltale mantle exchange zones are located, is recycled through the upwelling and subducting pipeline every 200 million years or so, which means hard evidence of tectonic origins was destroyed long ago.

Continental crust is older, and rocks dating back more than 4 billion years have been identified in places like Jack Hills, Australia. But continental plates float above the subductive fray, revealing little of the system’s origins.

Nevertheless, geoscientists are doing their best with extant rocks, models and laboratory experiments to sketch out possible tectonic timelines. Dr. Korenaga and his colleagues have proposed that plate tectonics began very early, right after Earth’s crust solidified from its initial magmatic state.

“That is when the conditions would have been easiest for plate tectonics to get started,” he said. At that point, he said, most of the water on Earth — delivered by comets — would still be on the surface, with little of it having found its way into the mantle. The heat convecting up through the mantle would exert a stronger force on dry rocks than on rocks that were lubricated.

At the same time, the surface water would make it easier for the hot, twisting rocks beneath to crack the surface lid apart, rather as a sprinkling of water from the faucet eases the task of popping ice cubes from a tray. The cracking open of the surface lid, Dr. Korenaga said, is key to getting the all-mighty subduction engine started. With subduction established, water, like oceanic crust, would cycle between Earth’s surface and mantle.

Water is constantly recycled between the mantle and crust

A map of tectonic plates in the Indian Ocean based on data showing seafloor gravity anomalies. The red areas show areas where gravity is stronger, largely aligning with underwater ridges, seamounts and plate edges. Credit Joshua Stevens, Sandwell, D. et al., NASA

On the opposite end of the origins debate is Dr. Stern, who argues that plate tectonics is a mere billion years old or less, and that Earth spent its first 3.5 billion years with a simple “single lid” as its outer shell: a crust riddled with volcanoes and other means of heat ventilation, but no moving plates, no subduction, no recycling between inside and out.

As evidence of the youthfulness of the plate regimen, Dr. Stern points to two classes of rocks: ophiolites and blueschist.

Ophiolites are pieces of oceanic crust atop bits of underlying mantle that have made their way onto land and thus have escaped the relentless recycling of oceanic crust. Recent research has shown that ophiolites are not just any slice of oceanic crust, Dr. Stern said, but rather were formed by the forces of subduction.

Similarly, blueschists are rocks that are fashioned under very high pressure but low temperatures, and “the only place you can do that is in a subduction zone,” Dr. Stern said.

Nearly all ophiolites are less than a billion years old, he added, while the most ancient blueschists, found in China, are just 800 million years old. No ophiolites, no blueschists, no evidence of subduction or plate tectonics.

Most geologists opt for a middle ground. “Science is a democratic process,” said Michael Brown, a geologist at the University of Maryland and an editor of the themed issue, “and the prevailing view is that Earth started to exhibit behaviors that look like plate tectonics 2.5 to 3 billion years ago.”

Significantly, that chronology decouples plate tectonics from the origin of life on Earth: evidence of the earliest single-celled organisms dates back more than 3.6 billion years. Nevertheless, scientists view plate tectonics as vital to the sustained evolution of that primordial life.

In Iceland, a visible fault between the North American and Eurasian plates, which are pulling away from each other at a rate of about an inch a year. Credit Universal History Archive/UIG, via Getty Images

Plate tectonic activity did not just help to stabilize Earth’s heat management system. The movement kept a steady supply of water shuttling between mantle and crust, rather than gradually evaporating from the surface.

It blocked the dangerous buildup of greenhouse gases in the atmosphere by sucking excess carbon from the ocean and subducting it underground. It shook up mountains and pulverized rocks, freeing up essential minerals and nutrients like phosphorus, oxygen and nitrogen for use in the growing carnival of life.

Dr. Zerkle discerns a link between geological and biological high drama: “It’s been suggested that time periods of supercontinental cycles — when small continents smash together to make large supercontinents, and those supercontinents then rip apart into smaller continents again — could have put large pulses of nutrients into the biosphere and allowed organisms to really take off.”

Plate tectonics also built the right playing fields for Darwinian games.

“Think about what drives evolution,” Dr. Stern said. “It’s isolation and competition. You need to break continents and continental shelves apart, and separate one ocean from another, for speciation to occur.”

Life is always falling apart, on the rocks — and a good thing, too.

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From Science Magazine: “Massive crater under Greenland’s ice points to climate-altering impact in the time of humans”

From Science Magazine

A 1.5-kilometer asteroid, intact or in pieces, may have smashed into an ice sheet just 13,000 years ago.
NASA SCIENTIFIC VISUALIZATION STUDIO

Nov. 14, 2018
Paul Voosen

On a bright July day 2 years ago, Kurt Kjær was in a helicopter flying over northwest Greenland—an expanse of ice, sheer white and sparkling. Soon, his target came into view: Hiawatha Glacier, a slow-moving sheet of ice more than a kilometer thick. It advances on the Arctic Ocean not in a straight wall, but in a conspicuous semicircle, as though spilling out of a basin. Kjær, a geologist at the Natural History Museum of Denmark in Copenhagen, suspected the glacier was hiding an explosive secret. The helicopter landed near the surging river that drains the glacier, sweeping out rocks from beneath it. Kjær had 18 hours to find the mineral crystals that would confirm his suspicions.

What he brought home clinched the case for a grand discovery. Hidden beneath Hiawatha is a 31-kilometer-wide impact crater, big enough to swallow Washington, D.C., Kjær and 21 co-authors report today in a paper in Science Advances. The crater was left when an iron asteroid 1.5 kilometers across slammed into Earth, possibly within the past 100,000 years.

Though not as cataclysmic as the dinosaur-killing Chicxulub impact, which carved out a 200-kilometer-wide crater in Mexico about 66 million years ago, the Hiawatha impactor, too, may have left an imprint on the planet’s history.

Artist’s reconstruction of Chicxulub crater soon after impact, 66 million years ago.
DETLEV VAN RAVENSWAAY/SCIENCE SOURCE

The timing is still up for debate, but some researchers on the discovery team believe the asteroid struck at a crucial moment: roughly 13,000 years ago, just as the world was thawing from the last ice age. That would mean it crashed into Earth when mammoths and other megafauna were in decline and people were spreading across North America.

The impact would have been a spectacle for anyone within 500 kilometers. A white fireball four times larger and three times brighter than the sun would have streaked across the sky. If the object struck an ice sheet, it would have tunneled through to the bedrock, vaporizing water and stone alike in a flash. The resulting explosion packed the energy of 700 1-megaton nuclear bombs, and even an observer hundreds of kilometers away would have experienced a buffeting shock wave, a monstrous thunder-clap, and hurricane-force winds. Later, rock debris might have rained down on North America and Europe, and the released steam, a greenhouse gas, could have locally warmed Greenland, melting even more ice.

The news of the impact discovery has reawakened an old debate among scientists who study ancient climate. A massive impact on the ice sheet would have sent meltwater pouring into the Atlantic Ocean—potentially disrupting the conveyor belt of ocean currents and causing temperatures to plunge, especially in the Northern Hemisphere. “What would it mean for species or life at the time? It’s a huge open question,” says Jennifer Marlon, a paleoclimatologist at Yale University.

A decade ago, a small group of scientists proposed a similar scenario [Science]. They were trying to explain a cooling event, more than 1000 years long, called the Younger Dryas, which began 12,800 years ago, as the last ice age was ending. Their controversial solution was to invoke an extraterrestrial agent: the impact of one or more comets. The researchers proposed that besides changing the plumbing of the North Atlantic, the impact also ignited wildfires across two continents that led to the extinction of large mammals and the disappearance of the mammoth-hunting Clovis people of North America. The research group marshaled suggestive but inconclusive evidence, and few other scientists were convinced. But the idea caught the public’s imagination despite an obvious limitation: No one could find an impact crater.

Proponents of a Younger Dryas impact now feel vindicated. “I’d unequivocally predict that this crater is the same age as the Younger Dryas,” says James Kennett, a marine geologist at the University of California, Santa Barbara, one of the idea’s original boosters.

But Jay Melosh, an impact crater expert at Purdue University in West Lafayette, Indiana, doubts the strike was so recent. Statistically, impacts the size of Hiawatha occur only every few million years, he says, and so the chance of one just 13,000 years ago is small. No matter who is right, the discovery will give ammunition to Younger Dryas impact theorists—and will turn the Hiawatha impactor into another type of projectile. “This is a hot potato,” Melosh tells Science. “You’re aware you’re going to set off a firestorm?”

It started with a hole. In 2015, Kjær and a colleague were studying a new map of the hidden contours under Greenland’s ice. Based on variations in the ice’s depth and surface flow patterns, the map offered a coarse suggestion of the bedrock topography—including the hint of a hole under Hiawatha.

Kjær recalled a massive iron meteorite in his museum’s courtyard, near where he parks his bicycle. Called Agpalilik, Inuit for “the Man,” the 20-ton rock is a fragment of an even larger meteorite, the Cape York, found in pieces on northwest Greenland by Western explorers but long used by Inuit people as a source of iron for harpoon tips and tools. Kjær wondered whether the meteorite might be a remnant of an impactor that dug the circular feature under Hiawatha. But he still wasn’t confident that it was an impact crater. He needed to see it more clearly with radar, which can penetrate ice and reflect off bedrock.

Kjær’s team began to work with Joseph MacGregor, a glaciologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who dug up archival radar data. MacGregor found that NASA aircraft often flew over the site on their way to survey Arctic sea ice, and the instruments were sometimes turned on, in test mode, on the way out. “That was pretty glorious,” MacGregor says.

The radar pictures more clearly showed what looked like the rim of a crater, but they were still too fuzzy in the middle. Many features on Earth’s surface, such as volcanic calderas, can masquerade as circles. But only impact craters contain central peaks and peak rings, which form at the center of a newborn crater when—like the splash of a stone in a pond—molten rock rebounds just after a strike. To look for those features, the researchers needed a dedicated radar mission.

Coincidentally, the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany, had just purchased a next-generation ice-penetrating radar to mount across the wings and body of their Basler aircraft, a twin-propeller retrofitted DC-3 that’s a workhorse of Arctic science. But they also needed financing and a base close to Hiawatha.

Kjær took care of the money. Traditional funding agencies would be too slow, or prone to leaking their idea, he thought. So he petitioned Copenhagen’s Carlsberg Foundation, which uses profits from its global beer sales to finance science. MacGregor, for his part, enlisted NASA colleagues to persuade the U.S. military to let them work out of Thule Air Base, a Cold War outpost on northern Greenland, where German members of the team had been trying to get permission to work for 20 years. “I had retired, very serious German scientists sending me happy-face emojis,” MacGregor says.

NASA and German aircraft used radar to see the contours of an impact crater beneath the ice of Hiawatha Glacier. JOHN SONNTAG/NASA

Three flights, in May 2016, added 1600 kilometers of fresh data from dozens of transits across the ice—and evidence that Kjær, MacGregor, and their team were onto something. The radar revealed five prominent bumps in the crater’s center, indicating a central peak rising some 50 meters high. And in a sign of a recent impact, the crater bottom is exceptionally jagged. If the asteroid had struck earlier than 100,000 years ago, when the area was ice free, erosion from melting ice farther inland would have scoured the crater smooth, MacGregor says. The radar signals also showed that the deep layers of ice were jumbled up—another sign of a recent impact. The oddly disturbed patterns, MacGregor says, suggest “the ice sheet hasn’t equilibrated with the presence of this impact crater.”

But the team wanted direct evidence to overcome the skepticism they knew would greet a claim for a massive young crater, one that seemed to defy the odds of how often large impacts happen. And that’s why Kjær found himself, on that bright July day in 2016, frenetically sampling rocks all along the crescent of terrain encircling Hiawatha’s face. His most crucial stop was in the middle of the semicircle, near the river, where he collected sediments that appeared to have come from the glacier’s interior. It was hectic, he says—”one of those days when you just check your samples, fall on the bed, and don’t rise for some time.”

In that outwash, Kjær’s team closed its case. Sifting through the sand, Adam Garde, a geologist at the Geological Survey of Denmark and Greenland in Copenhagen, found glass grains forged at temperatures higher than a volcanic eruption can generate. More important, he discovered shocked crystals of quartz. The crystals contained a distinctive banded pattern that can be formed only in the intense pressures of extraterrestrial impacts or nuclear weapons. The quartz makes the case, Melosh says. “It looks pretty good. All the evidence is pretty compelling.”

Now, the team needs to figure out exactly when the collision occurred and how it affected the planet.

The Younger Dryas, named after a small white and yellow arctic flower that flourished during the cold snap, has long fascinated scientists. Until human-driven global warming set in, that period reigned as one of the sharpest recent swings in temperature on Earth. As the last ice age waned, about 12,800 years ago, temperatures in parts of the Northern Hemisphere plunged by as much as 8°C, all the way back to ice age readings. They stayed that way for more than 1000 years, turning advancing forest back into tundra.

The trigger could have been a disruption in the conveyor belt of ocean currents, including the Gulf Stream that carries heat northward from the tropics. In a 1989 paper in Nature, Kennett, along with Wallace Broecker, a climate scientist at Columbia University’s Lamont-Doherty Earth Observatory, and others, laid out how meltwater from retreating ice sheets could have shut down the conveyor. As warm water from the tropics travels north at the surface, it cools while evaporation makes it saltier. Both factors boost the water’s density until it sinks into the abyss, helping to drive the conveyor. Adding a pulse of less-dense freshwater could hit the brakes. Paleoclimate researchers have largely endorsed the idea, although evidence for such a flood has been lacking until recently.

Then, in 2007, Kennett suggested a new trigger. He teamed up with scientists led by Richard Firestone, a physicist at Lawrence Berkeley National Laboratory in California, who proposed a comet strike at the key moment [PNAS]. Exploding over the ice sheet covering North America, the comet or comets would have tossed light-blocking dust into the sky, cooling the region. Farther south, fiery projectiles would have set forests alight, producing soot that deepened the gloom and the cooling. The impact also could have destabilized ice and unleashed meltwater that would have disrupted the Atlantic circulation.

The climate chaos, the team suggested, could explain why the Clovis settlements emptied and the megafauna vanished soon afterward. But the evidence was scanty. Firestone and his colleagues flagged thin sediment layers at dozens of archaeological sites in North America. Those sediments seemed to contain geochemical traces of an extraterrestrial impact, such as a peak in iridium, the exotic element that helped cement the case for a Chicxulub impact. The layers also yielded tiny beads of glass and iron—possible meteoritic debris—and heavy loads of soot and charcoal, indicating fires.

The team met immediate criticism. The decline of mammoths, giant sloths, and other species had started well before the Younger Dryas. In addition, no sign existed of a human die-off in North America, archaeologists said. The nomadic Clovis people wouldn’t have stayed long in any site. The distinctive spear points that marked their presence probably vanished not because the people died out, but rather because those weapons were no longer useful once the mammoths waned, says Vance Holliday, an archaeologist at The University of Arizona in Tucson. The impact hypothesis was trying to solve problems that didn’t need solving.

The geochemical evidence also began to erode. Outside scientists could not detect the iridium spike in the group’s samples. The beads were real, but they were abundant across many geological times, and soot and charcoal did not seem to spike at the time of the Younger Dryas. “They listed all these things that aren’t quite sufficient,” says Stein Jacobsen, a geochemist at Harvard University who studies craters.

Yet the impact hypothesis never quite died. Its proponents continued to study the putative debris layer at other sites in Europe and the Middle East. They also reported finding microscopic diamonds at different sites that, they say, could have been formed only by an impact. (Outside researchers question the claims of diamonds.)

Now, with the discovery of Hiawatha crater, “I think we have the smoking gun,” says Wendy Wolbach, a geochemist at De-Paul University in Chicago, Illinois, who has done work on fires during the era.

The impact would have melted 1500 gigatons of ice, the team estimates—about as much ice as Antarctica has lost because of global warming in the past decade. The local greenhouse effect from the released steam and the residual heat in the crater rock would have added more melt. Much of that freshwater could have ended up in the nearby Labrador Sea, a primary site pumping the Atlantic Ocean’s overturning circulation. “That potentially could perturb the circulation,” says Sophia Hines, a marine paleoclimatologist at Lamont-Doherty.

Leery of the earlier controversy, Kjær won’t endorse that scenario. “I’m not putting myself in front of that bandwagon,” he says. But in drafts of the paper, he admits, the team explicitly called out a possible connection between the Hiawatha impact and the Younger Dryas.

Banded patterns in the mineral quartz are diagnostic of shock waves from an extraterrestrial impact. ADAM GARDE, GEUS

The evidence starts with the ice. In the radar images, grit from distant volcanic eruptions makes some of the boundaries between seasonal layers stand out as bright reflections. Those bright layers can be matched to the same layers of grit in cataloged, dated ice cores from other parts of Greenland [Science]. Using that technique, Kjær’s team found that most ice in Hiawatha is perfectly layered through the past 11,700 years. But in the older, disturbed ice below, the bright reflections disappear. Tracing the deep layers, the team matched the jumble with debris-rich surface ice on Hiawatha’s edge that was previously dated to 12,800 years ago. “It was pretty self-consistent that the ice flow was heavily disturbed at or prior to the Younger Dryas,” MacGregor says.

Other lines of evidence also suggest Hiawatha could be the Younger Dryas impact [PNAS]. In 2013, Jacobsen examined an ice core from the center of Greenland, 1000 kilometers away. He was expecting to put the Younger Dryas impact theory to rest by showing that, 12,800 years ago, levels of metals that asteroid impacts tend to spread did not spike. Instead, he found a peak in platinum, similar to ones measured in samples from the crater site. “That suggests a connection to the Younger Dryas right there,” Jacobsen says.

For Broecker, the coincidences add up. He had first been intrigued by the Firestone paper, but quickly joined the ranks of naysayers. Advocates of the Younger Dryas impact pinned too much on it, he says: the fires, the extinction of the megafauna, the abandonment of the Clovis sites. “They put a bad shine on it.” But the platinum peak Jacobsen found, followed by the discovery of Hiawatha, has made him believe again. “It’s got to be the same thing,” he says.

Yet no one can be sure of the timing. The disturbed layers could reflect nothing more than normal stresses deep in the ice sheet. “We know all too well that older ice can be lost by shearing or melting at the base,” says Jeff Severinghaus, a paleoclimatologist at the Scripps Institution of Oceanography in San Diego, California. Richard Alley, a glaciologist at Pennsylvania State University in University Park, believes the impact is much older than 100,000 years and that a subglacial lake can explain the odd textures near the base of the ice. “The ice flow over growing and shrinking lakes interacting with rough topography might have produced fairly complex structures,” Alley says.

A recent impact should also have left its mark in the half-dozen deep ice cores drilled at other sites on Greenland, which document the 100,000 years of the current ice sheet’s history. Yet none exhibits the thin layer of rubble that a Hiawatha-size strike should have kicked up. “You really ought to see something,” Severinghaus says.

Brandon Johnson, a planetary scientist at Brown University, isn’t so sure. After seeing a draft of the study, Johnson, who models impacts on icy moons such as Europa and Enceladus, used his code to recreate an asteroid impact on a thick ice sheet. An impact digs a crater with a central peak like the one seen at Hiawatha, he found, but the ice suppresses the spread of rocky debris. “Initial results are that it goes a lot less far,” Johnson says.

In 2016, Kurt Kjær looked for evidence of an impact in sand washed out from underneath Hiawatha Glacier. He would find glassy beads and shocked crystals of quartz.
SVEND FUNDER

Even if the asteroid struck at the right moment, it might not have unleashed all the disasters envisioned by proponents of the Younger Dryas impact. “It’s too small and too far away to kill off the Pleistocene mammals in the continental United States,” Melosh says. And how a strike could spark flames in such a cold, barren region is hard to see. “I can’t imagine how something like this impact in this location could have caused massive fires in North America,” Marlon says.

It might not even have triggered the Younger Dryas. Ocean sediment cores show no trace of a surge of freshwater into the Labrador Sea from Greenland, says Lloyd Keigwin, a paleoclimatologist at the Woods Hole Oceanographic Institution in Massachusetts. The best recent evidence, he adds, suggests a flood into the Arctic Ocean through western Canada instead [Nature Geoscience].

An external trigger may be unnecessary in any case, Alley says. During the last ice age, the North Atlantic saw 25 other cooling spells, probably triggered by disruptions to the Atlantic’s overturning circulation. None of those spells, known as Dansgaard-Oeschger (D-O) events, was as severe as the Younger Dryas, but their frequency suggests an internal cycle played a role in the Younger Dryas, too. Even Broecker agrees that the impact was not the ultimate cause of the cooling. If D-O events represent abrupt transitions between two regular states of the ocean, he says, “you could say the ocean was approaching instability and somehow this event knocked it over.”

Still, Hiawatha’s full story will come down to its age. Even an exposed impact crater can be a challenge for dating, which requires capturing the moment when the impact altered existing rocks—not the original age of the impactor or its target. Kjær’s team has been trying. They fired lasers at the glassy spherules to release argon for dating, but the samples were too contaminated. The researchers are inspecting a blue crystal of the mineral apatite for lines left by the decay of uranium, but it’s a long shot. The team also found traces of carbon in other samples, which might someday yield a date, Kjær says. But the ultimate answer may require drilling through the ice to the crater floor, to rock that melted in the impact, resetting its radioactive clock. With large enough samples, researchers should be able to pin down Hiawatha’s age.

Given the remote location, a drilling expedition to the hole at the top of the world would be costly. But an understanding of recent climate history—and what a giant impact can do to the planet—is at stake. “Somebody’s got to go drill in there,” Keigwin says. “That’s all there is to it.”

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From ESA: “ESA’S GRAVITY-MAPPER REVEALS RELICS OF ANCIENT CONTINENTS UNDER ANTARCTIC ICE”

From European Space Agency

The shape curve indexes derived from GOCE gravity gradient measurements have been used to understand the plate tectonic movement in the Antarctic region and Earth in general. This animation shows the separation of Antarctica and Australia from ancient Gondwana, from 200 million years ago to the present. The new images help to link the cores of the these continents and contribute to a better understanding of these remote parts of the world.

7 November 2018

It was five years ago this month that ESA’s GOCE gravity-mapping satellite finally gave way to gravity, but its results are still yielding buried treasure – giving a new view of the remnants of lost continents hidden deep under the ice sheet of Antarctica.

ESA/GOCE Spacecraft

A research team from Germany’s Kiel University and the British Antarctic Survey published their latest GOCE-based findings this week in the journal Scientific Reports.

Dubbed ‘the Formula one of space’, the GOCE (Gravity field and Ocean Circulation Explorer) mission orbited Earth for more than four years, from March 2009 to November 2013. This sleek, finned satellite with no moving parts was designed around a single goal: to measure the pull of Earth’s gravity more precisely than any mission before.

GOCE flew at an altitude of just 255 km, more than 500 km nearer than a typical Earth observation satellite, to maximise its sensitivity to gravity.

In its last year in orbit, with its supply of xenon propellant holding out well, GOCE was manoeuvred down still lower, to just 225 km altitude, for even more accurate gravity measurements. The propellant keeping it resistant to air drag was finally spent in October 2013, and it reentered the atmosphere three weeks later.

GOCE’s main output was a high-fidelity global gravity map or ‘geoid’, but the mission also charted localised gravity gradients – measurements of how rapidly the acceleration of gravity changes – across all directions of motion, down to a resolution of 80 km.

The team from Kiel University and BAS has converted this patchwork of 3D gravity measurements into curvature-based ‘shape indexes’ across the different regions of our planet, analogous to contours on a map.

The study’s lead author Prof Jörg Ebbing from Kiel University comments, “The satellite gravity data can be combined with seismological data to produce more consistent images of the crust and upper mantle in 3D, which is crucial to understand how plate tectonics and deep mantle dynamics interact.”

GOCE’s global tectonic map.
This global tectonic map was created by researchers from Kiel University and the British Antarctic Survey using gravity gradients – the rate of change in the pull of gravity in different directions – measured by ESA’s GOCE gravity-mapping satellite. These gravity gradients were used to create a curvature-based shape index, analogous to contour lines on a map, which can be interpreted as a tectonic map of the Earth, as seen by GOCE. Surface topography is stripped away to reveal the deep structure of the continents and oceans. Geological similar tectonic domains can exhibit distinct differences in satellite gravity gradients maps, which point to differences in the lithosphere – the solid crust and the molten mantle beneath. In combination with seismological results, gravity-gradient imaging offers a new window on Earth’s structure. In this project, for the first time, seismological models and satellite observations are integrated to provide a consistent image of the crust and upper mantle in 3D, needed to understand the coupling of plate tectonics and mantle dynamics. In remote frontiers like the Antarctic continent, where even basic knowledge of lithospheric scale features remains incomplete, the curvature images help unveil the heterogeneity in lithospheric structure, e.g. between the composite East Antarctic Craton and the West Antarctic Rift System.

In combination with existing seismological data, these gravity gradients show high sensitivity to known features of Earth’s ‘lithosphere’, the solid crust and that section of the molten mantle beneath it.

These features include dense rocky zones called cratons – remnants of ancient continents found at the heart of modern continental plates – highly folded ‘orogen’ regions associated with mountain ranges and the thinner crust of ocean beds.

The new window into the deep subsurface offered by this data offers novel insights into the structure of all Earth’s continents, but especially Antarctica. With more than 98% of its surface covered by ice with an average thickness of 2 km, the southern continent largely remains a blank spot on current geological maps.

GOCE map of Antarctica on bedrock topography.
Gravity gradient shape index map of Antarctica draped on bedrock topography, derived from GOCE data. In remote frontiers like the Antarctic continent, where even basic knowledge of lithospheric scale features remains incomplete, GOCE’s new curvature images help unveil the difference in lithospheric structure between the dense craton composite of East Antarctica and the rift system of West Antarctica. These enhanced satellite gravity gradient images provide tantalising new insights for lithosphere and large-scale tectonic studies in the least understood continent on Earth. These enhanced images can additionally be used to understand the evolution of the plate tectonic evolution of the Antarctic region and Earth in general. The blue colours indicate ‘bowl’ features and the red colours indicate ‘dome’ features.

“These gravity images are revolutionising our ability to study the least understood continent on Earth, Antarctica,” says co-author Fausto Ferraccioli, Science Leader of Geology and Geophysics at BAS.

“In East Antarctica we see an exciting mosaic of geological features that reveal fundamental similarities and differences between the crust beneath Antarctica and other continents it was joined to until 160 million years ago.”

The gravity gradient findings show West Antarctica has a thinner crust and lithosphere compared to that of East Antarctica, which is made up of a mosaic of old cratons separated by younger orogens, revealing a family likeness to Australia and India.

These findings are of more than purely historic geological interest. They give clues to how Antarctica’s continental structure is influencing the behavior of ice sheets and how rapidly Antarctica regions will rebound in response to melting ice.

ESA’s GOCE mission scientist Roger Haagmans adds, “It is exciting to see that direct use of the gravity gradients, which were measured for the first time ever with GOCE, leads to a fresh independent look inside Earth – even below a thick sheet of ice.

“It also provides context of how continents were possibly connected in the past before they drifted apart owing to plate motion.”

See the full article here .

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The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

From Stanford University Engineering: “How will San Francisco’s skyscrapers fare after the next Big One?”

From Stanford University Engineering

November 06, 2018
Edmund L. Andrews

It’s not just about engineering a stronger building. It’s about designing a more resilient city. | Unsplash/Hardik Pandya

When Greg Deierlein looks at San Francisco’s skyline, he wonders: Will the city be ready if a major earthquake shakes those skyscrapers?

It’s not primarily a question of whether all the towers will remain standing, though there are some concerns about the ones built more than 30 years ago. The more complicated question is this, says Deierlein, the John A. Blume Professor in the School of Engineering: If one or more high-rises suffers serious damage, how badly could that disrupt the rest of the city?

“Traditionally, the building codes for seismic design have focused on collapse safety and preventing the loss of life,” he says. “A full reckoning should also take into account the potential costs during the recovery.” For instance, a single damaged high-rise apartment building could force hundreds of residents out of their homes for months — bad news for a city that’s already notoriously short on housing. Likewise, an office tower that becomes temporarily unusable could cost the city millions of dollars in lost economic activity. And should a damaged skyscraper be at risk of collapsing, it would pose a danger to everything in its shadow. “What,” Deierlein asks, “would be the cumulative effects of this disruption on the health and welfare of the city?”

The city of San Francisco wants to know, too. In recent years city officials have been developing a sweeping new strategy on earthquake preparedness for skyscrapers, the first such effort by a city in the United States, and Deierlein and his team have been providing city leaders with hard data and new modeling tools to better estimate the costs associated with disruption and downtime.

As a start, he and his colleagues, including Stanford PhD candidates Anne Hulsey and Wen-Yi Yen, inventoried 156 San Francisco buildings that rise 240 feet or more, noting their age, design and potential weaknesses. Their survey reveals that many high-rises built before 1990 were constructed with a type of steel frame that developed dangerous cracks in the welds during the 1994 Northridge earthquake in Los Angeles. Research by Hulsey and Yen aims to assess the risks posed to these pre-Northridge buildings and the surrounding neighborhoods. Retrofitting these older buildings would be enormously expensive, Deierlein says. Complicated, too.

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At the moment, owners are not required to complete new earthquake assessments, much less retrofits, unless they’re renovating at least two-thirds of a building. Most building owners carefully avoid hitting that trigger.
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Partly as a result of the building inventory, city officials have recommended changing the triggers that require property owners to reassess their seismic risks and requiring that future reassessments factor in building recovery time as well as safety.

San Francisco officials are also considering a number of recommendations for new buildings aimed at reducing downtime. These may include imposing tighter “drift limits” on the how much a building is permitted to sway in an earthquake, thereby reducing building damage and downtime. Another idea is to demand greater robustness in the building’s mechanical systems, from elevators and electrical systems to plumbing, which could reduce the time that all or part of a building is effectively unusable. They also propose requiring tall building owners to have a recovery plan that could include making advanced arrangements with engineers and contractors to repair damage after a quake.

One major obstacle is the status of the city’s current high-rise housing stock. San Francisco’s official goal is to make sure that 95% of the city’s high-rise housing can be restored to habitability within a few weeks after an earthquake. But studies by the Stanford team indicate that a damaged high-rise condominium could be uninhabitable for two to six months. Although the repairs themselves might indeed take only a few weeks, it could take several additional months to make a full damage assessment, get the proper permits and enlist the engineers and contractors.

The Stanford researchers also highlighted the possibility that a badly damaged skyscraper might force a city to cordon off all the streets and buildings in its shadow. In Christchurch, New Zealand, the central business district was shut down for more than two years after a 2011 earthquake. The San Francisco strategy calls for new protocols on setting up cordons, which are likely to be based in part on a model the Stanford team has developed to predict the risks.

The underlying theme of all this work, Deierlein says, is to look at skyscrapers as more than individual buildings. “It’s all about interconnectedness,” he says. “It’s not just about engineering a stronger building. Rather, it’s about designing a more resilient city by reducing damage and overcoming impeding factors that can interfere with recovery.”

See the full article here .

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Stanford University

Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

From The New York Times: “A.I. Is Helping Scientists Predict When and Where the Next Big Earthquake Will Be”

From The New York Times

Oct. 26, 2018

Thomas Fuller
Cade Metz

Jean-Francois Podevin

Countless dollars and entire scientific careers have been dedicated to predicting where and when the next big earthquake will strike. But unlike weather forecasting, which has significantly improved with the use of better satellites and more powerful mathematical models, earthquake prediction has been marred by repeated failure.

Some of the world’s most destructive earthquakes — China in 2008, Haiti in 2010 and Japan in 2011, among them — occurred in areas that seismic hazard maps had deemed relatively safe. The last large earthquake to strike Los Angeles, Northridge in 1994, occurred on a fault that did not appear on seismic maps.

Now, with the help of artificial intelligence, a growing number of scientists say changes in the way they can analyze massive amounts of seismic data can help them better understand earthquakes, anticipate how they will behave, and provide quicker and more accurate early warnings.

“I am actually hopeful for the first time in my career that we will make progress on this problem,” said Paul Johnson, a fellow at the Los Alamos National Laboratory who is among those at the forefront of this research.

Well aware of past earthquake prediction failures, scientists are cautious when asked how much progress they have made using A.I. Some in the field refer to prediction as “the P word,” because they do not even want to imply it is possible. But one important goal, they say, is to be able to provide reliable forecasts.

The earthquake probabilities that are provided on seismic hazard maps, for example, have crucial consequences, most notably in instructing engineers how they should construct buildings. Critics say these maps are remarkably inexact.

A map of Los Angeles lists the probability of an earthquake producing strong shaking within a given period of time — usually 50 years. That is based on a complex formula that takes into account, among other things, the distance from a fault, how fast one side of a fault is moving past the other, and the recurrence of earthquakes in the area.

A study led by Katherine M. Scharer, a geologist with the United States Geological Survey, estimated dates for nine previous earthquakes along the Southern California portion of the San Andreas fault dating back to the eighth century. The last big earthquake on the San Andreas was in 1857.

Since the average interval between these big earthquakes was 135 years, a common interpretation is that Southern California is due for a big earthquake. Yet the intervals between earthquakes are so varied — ranging from 44 years to 305 years — that taking the average is not a very useful prediction tool. A big earthquake could come tomorrow, or it could come in a century and a half or more.

This is one of the criticisms of Philip Stark, an associate dean at the University of California, Berkeley, at the Division of Mathematical and Physical Sciences. Dr. Stark describes the overall system of earthquake probabilities as “somewhere between meaningless and misleading” and has called for it to be scrapped.

The new A.I.-related earthquake research is leaning on neural networks, the same technology that has accelerated the progress of everything from talking digital assistants to driverless cars. Loosely modeled on the web of neurons in the human brain, a neural network is a complex mathematical system that can learn tasks on its own.

Scientists say seismic data is remarkably similar to the audio data that companies like Google and Amazon use in training neural networks to recognize spoken commands on coffee-table digital assistants like Alexa. When studying earthquakes, it is the computer looking for patterns in mountains of data rather than relying on the weary eyes of a scientist.

“Rather than a sequence of words, we have a sequence of ground-motion measurements,” said Zachary Ross, a researcher in the California Institute of Technology’s Seismological Laboratory who is exploring these A.I. techniques. “We are looking for the same kinds of patterns in this data.”

Brendan Meade, a professor of earth and planetary sciences at Harvard, began exploring these techniques after spending a sabbatical at Google, a company at the forefront of A.I. research.

His first project showed that, at the very least, these machine-learning methods could significantly accelerate his experiments. He and his graduate students used a neural network to run an earthquake analysis 500 times faster than they could in the past. What once took days now took minutes.

Dr. Meade also found that these A.I. techniques could lead to new insights. In the fall, with other researchers from Google and Harvard, he published a paper showing how neural networks can forecast earthquake aftershocks. This kind of project, he believes, represents an enormous shift in the way earthquake science is done. Similar work is underway at places like Caltech and Stanford University.

“We are at a point where the technology can do as well as — or better than — human experts,” Dr. Ross said.

Driving that guarded optimism is the belief that as sensors get smaller and cheaper, scientists will be able to gather larger amounts of seismic data. With help from neural networks and similar A.I. techniques, they hope to glean new insights from all this data.

Dr. Ross and other Caltech researchers are using these techniques to build systems that can more accurately recognize earthquakes as they are happening and anticipate where the epicenter is and where the shaking will spread.

Japan and Mexico have early warning systems, and California just rolled out its own. But scientists say artificial intelligence could greatly improve their accuracy, helping predict the direction and intensity of a rupture in the earth’s crust and providing earlier warnings to hospitals and other institutions that could benefit from a few extra seconds of preparation.

“The more detail you have, the better your forecasts will be,” Dr. Ross said.

Scientists working on these projects said neural networks have their limits. Though they are good at finding familiar signals in data, they are not necessarily suited to finding new kinds of signals — like the sounds tectonic plates make as they grind together.

But at Los Alamos, Dr. Johnson and his colleagues have shown that a machine-learning technique called “random forests” can identify previously unknown signals in a simulated fault created inside a lab. In one case, their system showed that a particular sound made by the fault, which scientists previously thought was meaningless, was actually an indication of when an earthquake would arrive.

Some scientists, like Robert Geller, a seismologist at the University of Tokyo, are unconvinced that A.I. will improve earthquake forecasts. He questions the very premise that past earthquakes can predict future ones. And ultimately, he said, we would only know the effectiveness of A.I. forecasting when earthquakes can be predicted beyond random chance.

“There are no shortcuts,” Dr. Geller said. “If you cannot predict the future, then your hypothesis is wrong.”

See the full article here .

Earthquake Alert

Earthquake Alert

Earthquake Network projectEarthquake Network is a research project which aims at developing and maintaining a crowdsourced smartphone-based earthquake warning system at a global level. Smartphones made available by the population are used to detect the earthquake waves using the on-board accelerometers. When an earthquake is detected, an earthquake warning is issued in order to alert the population not yet reached by the damaging waves of the earthquake.

The project started on January 1, 2013 with the release of the homonymous Android application Earthquake Network. The author of the research project and developer of the smartphone application is Francesco Finazzi of the University of Bergamo, Italy.

Get the app in the Google Play store.

Smartphone network spatial distribution (green and red dots) on December 4, 2015

Meet The Quake-Catcher Network

Quake-Catcher Network

The Quake-Catcher Network is a collaborative initiative for developing the world’s largest, low-cost strong-motion seismic network by utilizing sensors in and attached to internet-connected computers. With your help, the Quake-Catcher Network can provide better understanding of earthquakes, give early warning to schools, emergency response systems, and others. The Quake-Catcher Network also provides educational software designed to help teach about earthquakes and earthquake hazards.

After almost eight years at Stanford, and a year at CalTech, the QCN project is moving to the University of Southern California Dept. of Earth Sciences. QCN will be sponsored by the Incorporated Research Institutions for Seismology (IRIS) and the Southern California Earthquake Center (SCEC).

The Quake-Catcher Network is a distributed computing network that links volunteer hosted computers into a real-time motion sensing network. QCN is one of many scientific computing projects that runs on the world-renowned distributed computing platform Berkeley Open Infrastructure for Network Computing (BOINC).

The volunteer computers monitor vibrational sensors called MEMS accelerometers, and digitally transmit “triggers” to QCN’s servers whenever strong new motions are observed. QCN’s servers sift through these signals, and determine which ones represent earthquakes, and which ones represent cultural noise (like doors slamming, or trucks driving by).

There are two categories of sensors used by QCN: 1) internal mobile device sensors, and 2) external USB sensors.

Mobile Devices: MEMS sensors are often included in laptops, games, cell phones, and other electronic devices for hardware protection, navigation, and game control. When these devices are still and connected to QCN, QCN software monitors the internal accelerometer for strong new shaking. Unfortunately, these devices are rarely secured to the floor, so they may bounce around when a large earthquake occurs. While this is less than ideal for characterizing the regional ground shaking, many such sensors can still provide useful information about earthquake locations and magnitudes.

USB Sensors: MEMS sensors can be mounted to the floor and connected to a desktop computer via a USB cable. These sensors have several advantages over mobile device sensors. 1) By mounting them to the floor, they measure more reliable shaking than mobile devices. 2) These sensors typically have lower noise and better resolution of 3D motion. 3) Desktops are often left on and do not move. 4) The USB sensor is physically removed from the game, phone, or laptop, so human interaction with the device doesn’t reduce the sensors’ performance. 5) USB sensors can be aligned to North, so we know what direction the horizontal “X” and “Y” axes correspond to.

If you are a science teacher at a K-12 school, please apply for a free USB sensor and accompanying QCN software. QCN has been able to purchase sensors to donate to schools in need. If you are interested in donating to the program or requesting a sensor, click here.

BOINC is a leader in the field(s) of Distributed Computing, Grid Computing and Citizen Cyberscience.BOINC is more properly the Berkeley Open Infrastructure for Network Computing, developed at UC Berkeley.

Earthquake safety is a responsibility shared by billions worldwide. The Quake-Catcher Network (QCN) provides software so that individuals can join together to improve earthquake monitoring, earthquake awareness, and the science of earthquakes. The Quake-Catcher Network (QCN) links existing networked laptops and desktops in hopes to form the worlds largest strong-motion seismic network.

Below, the QCN Quake Catcher Network map

ShakeAlert: An Earthquake Early Warning System for the West Coast of the United States

The U. S. Geological Survey (USGS) along with a coalition of State and university partners is developing and testing an earthquake early warning (EEW) system called ShakeAlert for the west coast of the United States. Long term funding must be secured before the system can begin sending general public notifications, however, some limited pilot projects are active and more are being developed. The USGS has set the goal of beginning limited public notifications in 2018.

Watch a video describing how ShakeAlert works in English or Spanish.

The primary project partners include:

United States Geological Survey
California Governor’s Office of Emergency Services (CalOES)
California Geological Survey
California Institute of Technology
University of California Berkeley
University of Washington
University of Oregon
Gordon and Betty Moore Foundation

The Earthquake Threat

Earthquakes pose a national challenge because more than 143 million Americans live in areas of significant seismic risk across 39 states. Most of our Nation’s earthquake risk is concentrated on the West Coast of the United States. The Federal Emergency Management Agency (FEMA) has estimated the average annualized loss from earthquakes, nationwide, to be $5.3 billion, with 77 percent of that figure ($4.1 billion) coming from California, Washington, and Oregon, and 66 percent ($3.5 billion) from California alone. In the next 30 years, California has a 99.7 percent chance of a magnitude 6.7 or larger earthquake and the Pacific Northwest has a 10 percent chance of a magnitude 8 to 9 megathrust earthquake on the Cascadia subduction zone.

Part of the Solution

Today, the technology exists to detect earthquakes, so quickly, that an alert can reach some areas before strong shaking arrives. The purpose of the ShakeAlert system is to identify and characterize an earthquake a few seconds after it begins, calculate the likely intensity of ground shaking that will result, and deliver warnings to people and infrastructure in harm’s way. This can be done by detecting the first energy to radiate from an earthquake, the P-wave energy, which rarely causes damage. Using P-wave information, we first estimate the location and the magnitude of the earthquake. Then, the anticipated ground shaking across the region to be affected is estimated and a warning is provided to local populations. The method can provide warning before the S-wave arrives, bringing the strong shaking that usually causes most of the damage.

Studies of earthquake early warning methods in California have shown that the warning time would range from a few seconds to a few tens of seconds. ShakeAlert can give enough time to slow trains and taxiing planes, to prevent cars from entering bridges and tunnels, to move away from dangerous machines or chemicals in work environments and to take cover under a desk, or to automatically shut down and isolate industrial systems. Taking such actions before shaking starts can reduce damage and casualties during an earthquake. It can also prevent cascading failures in the aftermath of an event. For example, isolating utilities before shaking starts can reduce the number of fire initiations.

System Goal

The USGS will issue public warnings of potentially damaging earthquakes and provide warning parameter data to government agencies and private users on a region-by-region basis, as soon as the ShakeAlert system, its products, and its parametric data meet minimum quality and reliability standards in those geographic regions. The USGS has set the goal of beginning limited public notifications in 2018. Product availability will expand geographically via ANSS regional seismic networks, such that ShakeAlert products and warnings become available for all regions with dense seismic instrumentation.

Current Status

The West Coast ShakeAlert system is being developed by expanding and upgrading the infrastructure of regional seismic networks that are part of the Advanced National Seismic System (ANSS); the California Integrated Seismic Network (CISN) is made up of the Southern California Seismic Network, SCSN) and the Northern California Seismic System, NCSS and the Pacific Northwest Seismic Network (PNSN). This enables the USGS and ANSS to leverage their substantial investment in sensor networks, data telemetry systems, data processing centers, and software for earthquake monitoring activities residing in these network centers. The ShakeAlert system has been sending live alerts to “beta” users in California since January of 2012 and in the Pacific Northwest since February of 2015.

In February of 2016 the USGS, along with its partners, rolled-out the next-generation ShakeAlert early warning test system in California joined by Oregon and Washington in April 2017. This West Coast-wide “production prototype” has been designed for redundant, reliable operations. The system includes geographically distributed servers, and allows for automatic fail-over if connection is lost.

This next-generation system will not yet support public warnings but does allow selected early adopters to develop and deploy pilot implementations that take protective actions triggered by the ShakeAlert notifications in areas with sufficient sensor coverage.

Authorities

The USGS will develop and operate the ShakeAlert system, and issue public notifications under collaborative authorities with FEMA, as part of the National Earthquake Hazard Reduction Program, as enacted by the Earthquake Hazards Reduction Act of 1977, 42 U.S.C. §§ 7704 SEC. 2.

For More Information

Robert de Groot, ShakeAlert National Coordinator for Communication, Education, and Outreach
rdegroot@usgs.gov
626-583-7225

Learn more about EEW Research

ShakeAlert Fact Sheet

ShakeAlert Implementation Plan

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From Science Alert: “The USGS Has Just Listed These 18 North American Volcanoes as “Very High” Risk”

From Science Alert

26 OCT 2018
MIKE MCRAE

The US Geological Survey (USGS) has recently updated their assessment of potentially threatening volcanoes across the nation, making changes in light of more than a decade of fresh research.

First, the good news: all of that data has revealed a handful of volcanoes with minimal threat of causing wanton destruction can now be crossed off the list altogether.

The bad news? There are still 18 bad boys to keep a close eye on. And it’s probably not a huge surprise that 16 out of those are on the North American west coast.

The last time the USGS ranked volcanic threats was back in 2005. A lot has been discovered about geology since then, so the National Volcanic Threat Assessment figured it was time to go back to the list and double check their sums.

Given the US is one of the most volcanically active nations on the planet, eruptions are a way of life. Just ask Hawaii, which saw some spectacular displays from Kīlauea volcano earlier this year.

Kilauea volcano (Photo: U.S. Geological Survey via EPA-EFE)

An aerial view of the erupting Pu’u ‘O’o crater on Hawaii’s Kilauea volcano taken at dusk on June 29, 1983.
Credit: G.E. Ulrich, USGS

A calmer scene at Hawaii’s Kilauea volcano. Approximately August 8, 2018(United States Geological Survey)

Then there are those occasional cataclysmic time bombs on the North American continent itself, like Mount St. Helens in Washington, which took the lives of 57 people nearly 40 years ago.

Knowing which mountains are going to blow sky high in a local apocalypse and which are likely to be smoking duds informs authorities on how to plan for the worst.

So the USGS categorises volcanoes according to numerous factors that describe their threat, as either very low, low, moderate, high, and very high.

These levels don’t so much as describe their chances of erupting any time soon, as much as their impact should they did awaken in a pyrotechnic blaze of molten rock and ash plumes.

There’s the obvious lava flows and flying boulders to contend with, but billowing clouds of dust particles can interfere with air traffic, potentially costing hundreds of millions in cancelled flights and rerouting.

That’s not to mention toxic gases and fine particulates polluting the atmosphere, increasing health risks. Long after the fireworks die away, volcanoes can still cause immense damage in a variety of ways, depending on their remoteness.

Take Imuruk Lake for example. Its volcano sits out in the Alaskan wilds, where any ash-laden plume is unlikely to interfere with aircraft. Last seeing action around 300 CE, it’s way down the bottom of the list of potential threats at number 161.

It joins 20 other volcanoes in the lowest threat category, which now contains 11 fewer occupants than in the 2005 assessment.

All up, 20 volcanoes have had their risk demoted or removed altogether following their revaluation. Mt Washington in Oregon is now considered dead as a dodo, and just as likely to come back. So has the state’s Four Craters lava field.

But the 18 red-alert monsters that sit in the list of highest threats are the same ones that were identified in 2005.

Number one should come as no surprise. Kīlauea’s latest activity saw more than 700 homes and businesses destroyed, making it the most threatening volcano the US has to contend with right now.

Washington’s Mt Saint Helens and Mt Rainier follow close behind, with Redoubt Volcano in Alaska at number four and California’s Mt Shasta at number five.

Looking at the top 25, people might be somewhat relieved to see that the much-feared Yellowstone caldera doesn’t make the riskiest top 18, sitting at 21.

If you’re seeing a pattern, most of the most severe threats are on the US West Coast, with three of the 18 in California, five in Alaska, four in Washington and another four in Oregon.

None of this means it’s time to pack up and head to Florida. We wouldn’t recommend it anyway, what with their human-sized lizards prowling neighbourhoods, toxic algal blooms, and annual tropical storms building up steam.

But it does give scientists a better idea of what to prioritise in their research, and governments a good sense of where to put their money.

As populations swell, air traffic increases, and new kinds of technology and infrastructure stretch across the nation, there’s no doubt we’ll be seeing more additions to the high threat categories in future editions of the assessment.

Thankfully somebody is keeping a close eye on these sleeping giants.

See the full article here .

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From temblor: “The Whistle: Are We Ready for the Big One?”

From temblor

October 24, 2018

Jason R. Patton, Ph.D.
Ross Stein, Ph.D.
Volkan Sevilgen, M.Sc.

It Has Happened Before

The southern San Andreas fault (SSAF) is a plate boundary strike-slip fault, where the Pacific plate moves northward relative to the North America plate. There have been large earthquakes on this fault in historic time, including the 1857 Forth Tejon earthquake. This 1857 earthquake is estimated to have been a magnitude 7.9 earthquake (larger than the recent earthquake in Sulawesi, Indonesia). There is also a record of prehistoric earthquakes on this fault, spanning the past 5000 years (Weldon et al., 2004; Sharer et al., 2007). These authors have determined that the average time between earthquakes on the SSAF is 105 years. However, the time between earthquakes ranges from 31 – 165 years. This large variation in inter-event time periods makes it more difficult to know when the next “Big One” will happen.

The USGS prepares earthquake scenarios based on our knowledge about past earthquakes and how future earthquakes may behave based on our empirical knowledge. Below is a USGS scenario map for the part of the SSAF that ruptured in the 1857 Fort Tejon earthquake. The color scale represent relative earthquake shaking intensity based on the Modified Mercalli Intensity scale. Warmer colors represent areas of stronger ground shaking. While the map below is based on a computer model, this is a good estimate of how strongly the ground shook in 1957. Note how the strongest ground shaking is adjacent to the fault.

USGS Shakemap scenario map for the southern San Andreas fault, showing an estimate of shaking intensity from an earthquake similar in length and magnitude to the 1857 Fort Tejon earthquake. The part of the fault that slips in this scenario earthquake is shown as a black line, very similar to the known extent of the 1857 earthquake.

Several governments and non-governmental organizations prepare estimates of seismic hazard so that people can ensure their building codes are designed to mitigate these hazards. The Global Earthquake Model (GEM) is an example of our efforts to estimate seismic hazards on a global scale. Temblor.net uses the Global Earth Activity Rate (GEAR) model to provide estimates of seismic hazard at a global to local scale (Bird et al., 2015). GEAR blends quakes during the past 41 years with strain of the Earth’s crust as measured using Global Positioning System (GPS) observations.

Below is a map prepared using the temblor.net app. Seismicity from the past month, week, and day are shown as colored circles. The temblor app suggests that this region of San Bernardino, CA has an earthquake score of 93. To find out what your earthquake score is, enter your address in the app at temblor.net.

Earthquake Risk map for southern California, centered on the inland empire. Active faults are shown as red lines. Earthquakes from the past month are shown as circles.

We Imagine the Consequences

Earthquakes can cause damage to buildings and other infrastructure due to the shaking intensity. The closer to the earthquake, the higher the intensity. Buildings are located on different types of bedrock and this can amplify the shaking intensity in places. How do we know this? We have made direct observations of the damage from earthquakes.

There is ample evidence of what happens during earthquakes like what will occur on the SSAF someday. The same fault system, further north, has also ruptured in historic time. In 1868, the Hayward fault (a sister fault of the San Andreas) had an earthquake that caused extensive damage in the San Francisco Bay area. The USGS and the California Geological Survey are using the 150 year anniversary of this earthquake as a tool to educate the public about earthquake hazards along these active faults in northern California. Here is a short video about the HayWired Scenario. More can be learned about how to outsmart disaster at the “HayWired” website here.

Below is a photo from the aftermath of the 1868 Hayward fault earthquake.

This photo shows damage to “Pierce’s House,” a building damaged by the 1868 Hayward fault earthquake. Image source: Wikimedia Commons, public domain.

Another historic earthquake that caused extensive damage in California is the 1906 Great San Francisco earthquake, another San Andreas fault earthquake. The damage from this earthquake included building damage and fire. Fire is one of the most common damaging effects of an earthquake like what will happen someday on the SSAF.

Below is a photo showing damage to houses that were built on material that did not perform well during an earthquake.

Photo of houses following the 1906 San Francisco earthquake. Photo from National Archives Record Group 46, public domain.

The combination of hazard and exposure (people) is what we call risk. When people are exposed to earthquake hazards, they are at risk from damage due to those earthquakes. If there is an earthquake and nobody is there to experience the earthquake, there is no risk. One major difference between 1868, 1906, and today is that there are more people that live close to these earthquake faults. While the average number of earthquakes stays relatively constant through time, as the population grows in earthquake country, the risk also grows.

Do you live along the San Andreas or some other plate boundary fault? What about another kind of fault?

To learn more about your exposure to these hazards, visit temblor.net.

When is the next Big One?

We don’t know when the next southern San Andreas fault big earthquake will happen. Currently there are no scientifically demonstrated ways to predict earthquakes. We can use the frequency of past earthquakes and patterns of earthquake occurrence (current seismicity) to estimate the chance that an earthquake will occur over a period of time.

These estimates of future earthquake occurrence are called forecasts. Most people are familiar with weather forecasts, but we know much less about earthquakes than we do about weather. Because of this, earthquake forecasts may not have the same amount of accuracy that weather forecasts do. However, these forecasts are based on the latest cutting edge science about earthquakes and are monumentally better than simply tossing a coin. The cool thing about these forecasts is that the science behind them improves over time as we learn more about how earthquakes happen. This is another improvement over coin tosses, which flip pretty much the same as they did since coins were invented.

The Whistle is an upcoming series of broadcasts produced by the Empire Network, a collaboration between KVCR, PBS, and National Public Radio.

This four-part documentary series that dives into earthquake science, history, local and international earthquakes and tsunamis, California preparedness and immediate response, prevention, mitigation, retrofits, resilience, sustainability, conservation, incentives, challenges, new technologies… and solutions. Are we ready for the Big One?

The first episode airs on October 25 and we will learn about earthquakes and the San Andreas fault:

______________________________________________________
Earthquakes and the San Andreas fault. The Ring of Fire. What do we know about earthquakes today? What causes them, how often, why we know the Big One is due. Evolution of seismology and our understanding of earthquakes and plate tectonics. How did the First Nations and early European settlers deal with Earthquakes before modern technology? How dangerous is the threat and how much of an impact can a big earthquake cause? What will happen when the next big one hits?
______________________________________________________

Episode 2 covers how our immediate response might unfold during and following the Big One. Episode 3 reviews our knowledge of the current state of infrastructures (buildings, roads) and how an earthquake might impact these investments in society. Finally, the 4th episode presents an evaluation of how we have improved our ability to be resilient in the face of disasters from the Big One following decades of applying the scientific method to our observations of earthquakes. How will Earthquake Early Warning work and how will we benefit from this? Learn more by watching The Whistle.

The premiere for “The Whistle, Are We Ready for the Big One?” premieres on Thursday Oct. 25. Watch the first episode on television, or head to this website where the video will be available to stream online.

References

Bird, P., Jackson, D. D., Kagan, Y. Y., Kreemer, C., and Stein, R. S., 2015. GEAR1: A global earthquake activity rate model constructed from geodetic strain rates and smoothed seismicity, Bull. Seismol. Soc. Am., v. 105, no. 5, p. 2538–2554, DOI: 10.1785/0120150058

Sharer, K.M., Weldon, R.J.III., Fumal, T.E., and Biasi, G., 2007. Paleoearthquakes on the Southern San Andreas Fault, Wrightwood, California, 3000 to 1500 B.C.: A New Method for Evaluating Paleoseismic Evidence and Earthquake Horizons in Bull. Seismol. Soc. Am., v. 97, no. 4, p. 1054–1093, DOI: 10.1785/0120060137

Weldon, R., Sharer, K.M., Fumal, T., and Biasi, G., 2004. Wrightwood and the Earthquake Cycle: What a Long Recurrence Record Tells Us About How Faults Work in GSA Today, v. 14, no. 9, doi: 10.1130/1052-5173(2004)0142.0.CO;2

See the full article here .

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Earthquake Alert

Earthquake Alert

Earthquake Network project

Earthquake Network is a research project which aims at developing and maintaining a crowdsourced smartphone-based earthquake warning system at a global level. Smartphones made available by the population are used to detect the earthquake waves using the on-board accelerometers. When an earthquake is detected, an earthquake warning is issued in order to alert the population not yet reached by the damaging waves of the earthquake.

The project started on January 1, 2013 with the release of the homonymous Android application Earthquake Network. The author of the research project and developer of the smartphone application is Francesco Finazzi of the University of Bergamo, Italy.

Get the app in the Google Play store.

Smartphone network spatial distribution (green and red dots) on December 4, 2015

Meet The Quake-Catcher Network

Quake-Catcher Network

The Quake-Catcher Network is a collaborative initiative for developing the world’s largest, low-cost strong-motion seismic network by utilizing sensors in and attached to internet-connected computers. With your help, the Quake-Catcher Network can provide better understanding of earthquakes, give early warning to schools, emergency response systems, and others. The Quake-Catcher Network also provides educational software designed to help teach about earthquakes and earthquake hazards.

After almost eight years at Stanford, and a year at CalTech, the QCN project is moving to the University of Southern California Dept. of Earth Sciences. QCN will be sponsored by the Incorporated Research Institutions for Seismology (IRIS) and the Southern California Earthquake Center (SCEC).

The Quake-Catcher Network is a distributed computing network that links volunteer hosted computers into a real-time motion sensing network. QCN is one of many scientific computing projects that runs on the world-renowned distributed computing platform Berkeley Open Infrastructure for Network Computing (BOINC).

The volunteer computers monitor vibrational sensors called MEMS accelerometers, and digitally transmit “triggers” to QCN’s servers whenever strong new motions are observed. QCN’s servers sift through these signals, and determine which ones represent earthquakes, and which ones represent cultural noise (like doors slamming, or trucks driving by).

There are two categories of sensors used by QCN: 1) internal mobile device sensors, and 2) external USB sensors.

Mobile Devices: MEMS sensors are often included in laptops, games, cell phones, and other electronic devices for hardware protection, navigation, and game control. When these devices are still and connected to QCN, QCN software monitors the internal accelerometer for strong new shaking. Unfortunately, these devices are rarely secured to the floor, so they may bounce around when a large earthquake occurs. While this is less than ideal for characterizing the regional ground shaking, many such sensors can still provide useful information about earthquake locations and magnitudes.

USB Sensors: MEMS sensors can be mounted to the floor and connected to a desktop computer via a USB cable. These sensors have several advantages over mobile device sensors. 1) By mounting them to the floor, they measure more reliable shaking than mobile devices. 2) These sensors typically have lower noise and better resolution of 3D motion. 3) Desktops are often left on and do not move. 4) The USB sensor is physically removed from the game, phone, or laptop, so human interaction with the device doesn’t reduce the sensors’ performance. 5) USB sensors can be aligned to North, so we know what direction the horizontal “X” and “Y” axes correspond to.

If you are a science teacher at a K-12 school, please apply for a free USB sensor and accompanying QCN software. QCN has been able to purchase sensors to donate to schools in need. If you are interested in donating to the program or requesting a sensor, click here.

BOINC is a leader in the field(s) of Distributed Computing, Grid Computing and Citizen Cyberscience.BOINC is more properly the Berkeley Open Infrastructure for Network Computing, developed at UC Berkeley.

Earthquake safety is a responsibility shared by billions worldwide. The Quake-Catcher Network (QCN) provides software so that individuals can join together to improve earthquake monitoring, earthquake awareness, and the science of earthquakes. The Quake-Catcher Network (QCN) links existing networked laptops and desktops in hopes to form the worlds largest strong-motion seismic network.

Below, the QCN Quake Catcher Network map

ShakeAlert: An Earthquake Early Warning System for the West Coast of the United States

The U. S. Geological Survey (USGS) along with a coalition of State and university partners is developing and testing an earthquake early warning (EEW) system called ShakeAlert for the west coast of the United States. Long term funding must be secured before the system can begin sending general public notifications, however, some limited pilot projects are active and more are being developed. The USGS has set the goal of beginning limited public notifications in 2018.

Watch a video describing how ShakeAlert works in English or Spanish.

The primary project partners include:

United States Geological Survey
California Governor’s Office of Emergency Services (CalOES)
California Geological Survey
California Institute of Technology
University of California Berkeley
University of Washington
University of Oregon
Gordon and Betty Moore Foundation

The Earthquake Threat

Earthquakes pose a national challenge because more than 143 million Americans live in areas of significant seismic risk across 39 states. Most of our Nation’s earthquake risk is concentrated on the West Coast of the United States. The Federal Emergency Management Agency (FEMA) has estimated the average annualized loss from earthquakes, nationwide, to be $5.3 billion, with 77 percent of that figure ($4.1 billion) coming from California, Washington, and Oregon, and 66 percent ($3.5 billion) from California alone. In the next 30 years, California has a 99.7 percent chance of a magnitude 6.7 or larger earthquake and the Pacific Northwest has a 10 percent chance of a magnitude 8 to 9 megathrust earthquake on the Cascadia subduction zone.

Part of the Solution

Today, the technology exists to detect earthquakes, so quickly, that an alert can reach some areas before strong shaking arrives. The purpose of the ShakeAlert system is to identify and characterize an earthquake a few seconds after it begins, calculate the likely intensity of ground shaking that will result, and deliver warnings to people and infrastructure in harm’s way. This can be done by detecting the first energy to radiate from an earthquake, the P-wave energy, which rarely causes damage. Using P-wave information, we first estimate the location and the magnitude of the earthquake. Then, the anticipated ground shaking across the region to be affected is estimated and a warning is provided to local populations. The method can provide warning before the S-wave arrives, bringing the strong shaking that usually causes most of the damage.

Studies of earthquake early warning methods in California have shown that the warning time would range from a few seconds to a few tens of seconds. ShakeAlert can give enough time to slow trains and taxiing planes, to prevent cars from entering bridges and tunnels, to move away from dangerous machines or chemicals in work environments and to take cover under a desk, or to automatically shut down and isolate industrial systems. Taking such actions before shaking starts can reduce damage and casualties during an earthquake. It can also prevent cascading failures in the aftermath of an event. For example, isolating utilities before shaking starts can reduce the number of fire initiations.

System Goal

The USGS will issue public warnings of potentially damaging earthquakes and provide warning parameter data to government agencies and private users on a region-by-region basis, as soon as the ShakeAlert system, its products, and its parametric data meet minimum quality and reliability standards in those geographic regions. The USGS has set the goal of beginning limited public notifications in 2018. Product availability will expand geographically via ANSS regional seismic networks, such that ShakeAlert products and warnings become available for all regions with dense seismic instrumentation.

Current Status

The West Coast ShakeAlert system is being developed by expanding and upgrading the infrastructure of regional seismic networks that are part of the Advanced National Seismic System (ANSS); the California Integrated Seismic Network (CISN) is made up of the Southern California Seismic Network, SCSN) and the Northern California Seismic System, NCSS and the Pacific Northwest Seismic Network (PNSN). This enables the USGS and ANSS to leverage their substantial investment in sensor networks, data telemetry systems, data processing centers, and software for earthquake monitoring activities residing in these network centers. The ShakeAlert system has been sending live alerts to “beta” users in California since January of 2012 and in the Pacific Northwest since February of 2015.

In February of 2016 the USGS, along with its partners, rolled-out the next-generation ShakeAlert early warning test system in California joined by Oregon and Washington in April 2017. This West Coast-wide “production prototype” has been designed for redundant, reliable operations. The system includes geographically distributed servers, and allows for automatic fail-over if connection is lost.

This next-generation system will not yet support public warnings but does allow selected early adopters to develop and deploy pilot implementations that take protective actions triggered by the ShakeAlert notifications in areas with sufficient sensor coverage.

Authorities

The USGS will develop and operate the ShakeAlert system, and issue public notifications under collaborative authorities with FEMA, as part of the National Earthquake Hazard Reduction Program, as enacted by the Earthquake Hazards Reduction Act of 1977, 42 U.S.C. §§ 7704 SEC. 2.

For More Information

Robert de Groot, ShakeAlert National Coordinator for Communication, Education, and Outreach
rdegroot@usgs.gov
626-583-7225

Learn more about EEW Research

ShakeAlert Fact Sheet

ShakeAlert Implementation Plan