From temblor: “Large Earthquake in Papua New Guinea re-ruptures major fault in just 19 years: More to follow?”

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From temblor

May 19, 2019
Tiegan Hobbs, Ph.D., Postdoctoral Seismic Risk Scientist at Natural Resources Canada (@THobbsGeo)

A magnitude-7.5 quake broke the same fault that produced a magnitude-8.0 quake in 2000, an extraordinarily short recurrence time that also broke all our rules.

A major earthquake struck eastern Papua New Guinea (PNG) on Tuesday, May 14th at 22:58 local time. No injuries have been reported, although shaking from this Mw 7.5 earthquake was felt up to 250 km (150 mi) away from the epicenter. The maximum shaking intensity (the so-called ‘Modified Mercalli level VII’) would have been sufficient to cause considerable damage in poorly built houses which are common in the region.

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Map showing the location of the 14 May 2019 Mw 7.5 Papua New Guinea Earthquake, as well as the M=7.1 quake on the other side of the country, which struck just a week beforehand.

According to Dr. Baptiste Gombert, postdoctoral researcher at Oxford University, the event “occurred on the left-lateral Weitin fault [WF in the map below], a major structure of the New Ireland”. ‘Left-lateral’ means that whatever side you are on, the other side moved to the left. This fault marks the boundary between the North and South Bismarck microplates.

Beyond the Weitin Fault, this region has “every type of plate boundary” according to Dr. Jason Patton from the California Geological Survey and Adjunct Professor at Humboldt State University. For example, compression and shear between the Pacific and Australian Plates results in subduction along the New Britain Trench, rifting in the Woodlark Basin in addition to the observed strike-slip activity in the area of Tuesday’s quake.

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Modified from Holm et al., [2019], this map shows the regional tectonics. Looking like broken shards of glass, there is a complex interaction of possibly inactive subduction from the north and south, along with rifting, subduction, thrusting, and strike slip faults in between. The USGS moment tensor (beachball) from Tuesday’s Mw 7.5 event (blue star) suggests left-lateral motion on the Weitin Fault between the North and South Bismarck Plates. The event rattled residents of New Ireland (NI), the elongate island through which the Weitin Fault runs.

First Ever Measurement of Onshore Repeated Rupture

What makes this event so exciting, though, is that it’s not the first major earthquake in this location. A Mw 8.0 event in the year 2000 resulted in up to 11 m of slip along a 275-km-long (165 mi) fault, with 20 aftershocks with magnitude greater than 5 [Tregoning et al., 2001]. The proximity of this week’s hypocenter to the larger quake 19 years ago had Dr. Sotiris Valkaniotis, geological consultant, wondering if they ruptured the same portion of the fault. With some quick work processing satellite imagery, Dr. Valkaniotis produced what is believed to be the first recording of repeated on-land rupture of a fault.

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And we have slip! Co-seismic displacement on Weitin Fault, New Ireland, #PNG after the strong M7.5 May 15 2019 #earthquake. Displacement analysis from optical image correlation using #Sentinel2 images from @CopernicusEU and #MicMac. Repeat rupture on the same fault as 2000! pic.twitter.com/5PFZdfOdPj

— Sotiris Valkaniotis (@SotisValkan) May 16, 2019
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The figure in the above tweet, reproduced below, shows several meters of offset across the fault for both earthquakes. It’s preliminary, but it suggests that this fault is extremely active. For reference, Dr. Gombert describes the Weitin Fault as having a strain rate that is approximately 4 times that of the San Andreas in California. That’s important, because it presents a rare opportunity to study an entire seismic cycle from one large earthquake to the next in under 20 years—which appears to be unprecedented. These observations could help answer important questions about whether earthquakes repeatedly rupture the same patch, and what tends to initiate these events. In many places, such as the Cascadia Subduction Zone with its roughly 500-year recurrence period, this is simply not possible.

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Surface displacements in the North-South direction for the most recent Mw 7.5 event and the 2000 Mw 8.0 event on the Weitin Fault. Measurements made using optical correlation of Sentinel-2 and Landsat-7 satellite data.

2000 Mw 8.0 Event Triggered Large Nearby Earthquakes

Within 40 hours of the 16 November 2000 earthquake on the Weitin Fault, which was itself preceded by a 29 October 2000 Mw 6.8 foreshock, two events of magnitude 7.4 and 7.5 were recorded nearby [Park & Mori, 2007]. The events were found to be consistent with static stress triggering from the mainshock, and with a previous observation of Lay and Kanamori [1980] that earthquakes in this part of the world tend to occur in doublets: two large mainshocks that are close in space and time rather than the typical mainshock-aftershock sequence. It begs the question “will there be more?”

Triggering of Aftershocks From This Sequence?

Three strong aftershocks have so far struck near the mainshock: two Mw 5.0 events on Tuesday May 14th and Thursday May 16th, and a Mw 6.0 on Friday May 17th. Although we don’t yet know the type of faulting that occurred in these events, we can evaluate how the Mw 7.5 mainshock may have promoted them. A Coulomb Stress calculation shows that the epicentral locations of these events experienced stress loading of 112, 4, and 2 bars, respectively, assuming a similar fault geometry. This is well in excess of a 1 bar triggering threshold, suggesting that all three of these fault locations were brought closer to failure by the mainshock. In the map below, regions of red shading indicate areas prone to aftershocks – extending along an over 100 km swath of New Ireland. Given that the previous event in 2000 was able to trigger relatively large earthquakes on the Weitin [Geist and Parsons, 2005], the coming days and weeks could bring more large events to the region.

Without doubt, the data from this earthquake sequence will illuminate the stress evolution of this rapidly straining strike-slip fault and serve as a helpful natural laboratory for understanding similar strike-slip systems which are slower to reveal their mysteries.

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Stress change caused by the 14 May 2019 mainshock (green star), for faults with similar orientation. Red indicates areas of positive Coulomb stress change (up to 5 bars), and cyan shows regions with negative stress change (to -5 bars). The two Mw 5.0 and one Mw 6.0 aftershocks (white diamonds) experienced Coulomb stress loading upwards of the triggering threshold.

Tsunami Warnings for Papua New Guinea and the Solomon Islands

Strike-slip faults, like the Weitin and the San Andreas in California, generate dominantly horizontal motions, and so are fortunately unlikely to launch large tsunami unless they trigger undersea landslides. Some 9 minutes after the earthquake started, the Pacific Tsunami Warning Center assessed a tsunami threat for regions within 1000 km of the quake: mainly Papua New Guinea and the Solomon Islands. The threat was called off within about an hour and a half, with wave heights reaching less than 0.3 m (about a foot).

It is important to remember in the coming days and weeks, however, that aftershocks are also capable of producing dangerous tsunami. Following the Mw 8.0 New Ireland earthquake on the same fault in 2000, runups from the mainshock and triggered aftershocks were greater than 3 meters (9 feet) in some locations [Geist and Parsons, 2005]. This was partly due to the thrust mechanism of the aftershocks, which causes greater vertical displacement and therefore larger potential for tsunami. Because many populations in this region live close to the coast, the safest strategy is self-evacuation. This means that if you feel shaking that is strong or long, head to high ground without waiting to be told.

Read More:

USGS reports

https://earthquake.usgs.gov/earthquakes/eventpage/us70003kyy/executive

https://earthquake.usgs.gov/earthquakes/eventpage/us70003l05/executive

https://earthquake.usgs.gov/earthquakes/eventpage/usd000a1im/executive

https://earthquake.usgs.gov/earthquakes/eventpage/us70003mus/executive

Tsunami warnings

https://www.tsunami.gov/events/PHEB/2019/05/14/19134000/1/WEPA40/WEPA40.txt

https://www.tsunami.gov/events/PHEB/2019/05/14/19134000/3/WEPA40/WEPA40.txt

Social Media:

https://twitter.com/SotisValkan/status/1129069849131401216 (imagery based surface displacement measurement comparison)

Geist, E. L., & Parsons, T. (2005). Triggering of tsunamigenic aftershocks from large strike‐slip earthquakes: Analysis of the November 2000 New Ireland earthquake sequence. Geochemistry, Geophysics, Geosystems, 6(10).

Holm, R. J., Tapster, S., Jelsma, H. A., Rosenbaum, G., & Mark, D. F. (2019). Tectonic evolution and copper-gold metallogenesis of the Papua New Guinea and Solomon Islands region. Ore Geology Reviews, 104, 208-226.

Lay, T., & Kanamori, H. (1980). Earthquake doublets in the Solomon Islands. Physics of the Earth and Planetary Interiors, 21(4), 283-304.

Park, S. C., & Mori, J. (2007). Triggering of earthquakes during the 2000 Papua New Guinea earthquake sequence. Journal of Geophysical Research: Solid Earth, 112(B3).

Tregoning, P., McQueen, H., Lambeck, K., Stanaway, R., Saunders, S., Itikarai, I., Nohou, J., Curley, B., Suat, J. (2001). Progress Report on Geodetic Monitoring of the November 16, 2000 – New Ireland Earthquake. Australian National University, Research School of Earth Sciences, Special Report 2001/3. http://rses.anu.edu.au/geodynamics/tregoning/RSES_SR_2001-3.pdf

See the full article here .


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Earthquake Alert

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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.

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

Meet The Quake-Catcher Network

QCN bloc

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
QCN Quake Catcher Network map

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