From Argonne National Laboratory ALCF: “ALCF supercomputers advance earthquake modeling efforts”

News from Argonne National Laboratory

ALCF

May 1, 2018
John Spizzirri

Southern California defines cool. The perfect climes of San Diego, the glitz of Hollywood, the magic of Disneyland. The geology is pretty spectacular, as well.

“Southern California is a prime natural laboratory to study active earthquake processes,” says Tom Jordan, a professor in the Department of Earth Sciences at the University of Southern California (USC). “The desert allows you to observe the fault system very nicely.”

The fault system to which he is referring is the San Andreas, among the more famous fault systems in the world. With roots deep in Mexico, it scars California from the Salton Sea in the south to Cape Mendocino in the north, where it then takes a westerly dive into the Pacific.

Situated as it is at the heart of the San Andreas Fault System, Southern California does make an ideal location to study earthquakes. That it is home to nearly 24-million people makes for a more urgent reason to study them.

San Andreas Fault System. Aerial photo of San Andreas Fault looking northwest onto the Carrizo Plain with Soda Lake visible at the upper left. John Wiley User:Jw4nvc – Santa Barbara, California

USGS diagram of San Andreas Fault. http://nationalatlas.gov/articles/geology/features/sanandreas.html

Jordan and a team from the Southern California Earthquake Center (SCEC) are using the supercomputing resources of the Argonne Leadership Computing Facility (ALCF), a U.S. Department of Energy Office of Science User Facility, to advance modeling for the study of earthquake risk and how to reduce it.

Headquartered at USC, the center is one of the largest collaborations in geoscience, engaging over 70 research institutions and 1,000 investigators from around the world.

The team relies on a century’s worth of data from instrumental records as well as regional and seismic national hazard models to develop new tools for understanding earthquake hazards. Working with the ALCF, they have used this information to improve their earthquake rupture simulator, RSQSim.

RSQ is a reference to rate- and state-dependent friction in earthquakes — a friction law that can be used to study the nucleation, or initiation, of earthquakes. RSQSim models both nucleation and rupture processes to understand how earthquakes transfer stress to other faults.

ALCF staff were instrumental in adapting the code to Mira, the facility’s 10-petaflops supercomputer, to allow for the larger simulations required to model earthquake behaviors in very complex fault systems, like San Andreas, and which led to the team’s biggest discovery.

Shake, rattle, and code

The SCEC, in partnership with the U.S. Geological Survey, had already developed the Uniform California Earthquake Rupture Forecast (UCERF), an empirically based model that integrates theory, geologic information, and geodetic data, like GPS displacements, to determine spatial relationships between faults and slippage rates of the tectonic plates that created those faults.

Though more traditional, the newest version, UCERF3, is considered the best representation of California earthquake ruptures, but the picture it portrays is still not as accurate as researchers would hope.

“We know a lot about how big earthquakes can be, how frequently they occur, and where they occur, but we cannot predict them precisely in time,” notes Jordan.

The team turned to Mira to run RSQSim to determine whether they could achieve more accurate results more quickly. A physics-based code, RSQSim produces long-term synthetic earthquake catalogs that comprise dates, times, locations, and magnitudes for predicted events.

Using simulation, researchers impose stresses upon some representation of a fault system, which changes the stress throughout much of the system and thus changes the way future earthquakes occur. Trying to model these powerful stress-mediated interactions is particularly difficult with complex systems and faults like San Andreas.

“We just let the system evolve and create earthquake catalogs for a hundred thousand or a million years. It’s like throwing a grain of sand in a set of cogs to see what happens,” explains Christine Goulet, a team member and executive science director for special projects with SCEC.

The end result is a more detailed picture of the possible hazard, which forecasts a sequence of earthquakes of various magnitudes expected to occur on the San Andreas Fault over a given time range.

The group tried to calibrate RSQSim’s numerous parameters to replicate UCERF3, but eventually decided to run the code with its default parameters. While the initial intent was to evaluate the magnitude of differences between the models, they discovered, instead, that both models agreed closely on their forecasts of future seismologic activity.

“So it was an a-ha moment. Eureka,” recalls Goulet. “The results were a surprise because the group had thought carefully about optimizing the parameters. The decision not to change them from their default values made for very nice results.”

The researchers noted that the mutual validation of the two approaches could prove extremely productive in further assessing seismic hazard estimates and their uncertainties.

Information derived from the simulations will help the team compute the strong ground motions generated by faulting that occurs at the surface — the characteristic shaking that is synonymous with earthquakes. To do this, the team couples the earthquake rupture forecasts, UCERF and RSQSim, with different models that represent the way waves propagate through the system. Called ground motion prediction equations, these are standard equations used by engineers to calculate the shaking levels from earthquakes of different sizes and locations.

One of those models is the dynamic rupture and wave propagation code Waveqlab3D (Finite Difference Quake and Wave Laboratory 3D), which is the focus of the SCEC team’s current ALCF allocation.

“These experiments show that the physics-based model RSQSim can replicate the seismic hazard estimates derived from the empirical model UCERF3, but with far fewer statistical assumptions,” notes Jordan. “The agreement gives us more confidence that the seismic hazard models for California are consistent with what we know about earthquake physics. We can now begin to use these physics to improve the hazard models.”

This project was awarded computing time and resources at the ALCF through DOE’s Innovative and Novel Computational Impact on Theory and Experiment (INCITE) program. The team’s research is also supported by the National Science Foundation, the U.S. Geological Survey, and the W.M. Keck Foundation.

ANL ALCF Cetus IBM supercomputer

ANL ALCF Theta Cray supercomputer

ANL ALCF Cray Aurora supercomputer

ANL ALCF MIRA IBM Blue Gene Q supercomputer at the Argonne Leadership Computing Facility

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

Please help promote STEM in your local schools.

Stem Education Coalition

Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science. For more visit http://www.anl.gov.

About ALCF

The Argonne Leadership Computing Facility’s (ALCF) mission is to accelerate major scientific discoveries and engineering breakthroughs for humanity by designing and providing world-leading computing facilities in partnership with the computational science community.

We help researchers solve some of the world’s largest and most complex problems with our unique combination of supercomputing resources and expertise.

ALCF projects cover many scientific disciplines, ranging from chemistry and biology to physics and materials science. Examples include modeling and simulation efforts to:

Discover new materials for batteries
Predict the impacts of global climate change
Unravel the origins of the universe
Develop renewable energy technologies

Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science

From popsci.com: “Extreme Science: The San Andreas Fault” 2015 but important

Popular Science

August 19, 2015 [Just found this in social media.]
Mary Beth Griggs

How California is predicting and preparing for the inevitable. No image credit.

There’s a crack in California. It stretches for 800 miles, from the Salton Sea in the south, to Cape Mendocino in the north. It runs through vineyards and subway stations, power lines and water mains. Millions live and work alongside the crack, many passing over it (966 roads cross the line) every day. For most, it warrants hardly a thought. Yet in an instant, that crack, the San Andreas fault line, could ruin lives and cripple the national economy.

In one scenario produced by the United States Geological Survey, researchers found that a big quake along the San Andreas could kill 1,800 people, injure 55,000 and wreak $200 million in damage. It could take years, nearly a decade, for California to recover.

On the bright side, during the process of building and maintaining all that infrastructure that crosses the fault, geologists have gotten an up-close and personal look at it over the past several decades, contributing to a growing and extensive body of work. While the future remains uncertain (no one can predict when an earthquake will strike) people living near the fault are better prepared than they have ever been before.

The Trouble With Faults

All of the land on Earth, including the ocean floors, is divided into relatively thin, brittle segments of rock that float on top of a much thicker layer of softer rock called the mantle. The largest of these segments are called tectonic plates, and roughly correspond with the continents and subcontinents of the earth.

The San Andreas fault is a boundary between two of these tectonic plates. In California, along the fault, the two plates–the Pacific plate and the North American plate–are rubbing past each other, like you might slip by someone in a crowded room. The Pacific plate is moving generally northwest, headed towards Alaska and Japan, while the North American plate heads southwest.

In a simplified, ideal world, this movement would happen easily and smoothly. Because it covers such a large area, not all of the fault moves at the same time. In the middle, things are moving rather smoothly, with part of the Pacific plate gliding by the North American plate with relative ease, a segment that scientists say is ‘creeping’.

It’s at the northern and southern extremes where things get tricky. The real problems begin when the plates get stuck, or wedged together.

Visions Of A Disaster

The fear of a huge earthquake from the San Andreas devastating the west coast has been rich fodder for disaster films, including Superman and, more recently, San Andreas. The good news is that the worst-case scenarios in those films are completely impossible. California will not sink into the sea, and even the largest possible earthquake is short of anything that the Rock had to wrestle with.

But disasters have happened.

In 1906, the northern segment of the fault, near the city of San Francisco, ruptured along nearly 300 miles, causing a huge earthquake that led to fires, downed buildings, and thousands of casualties. The death toll was between 700 and 2,800.

Meanwhile, other segments of the fault, like one south of Los Angeles that hasn’t seen a large earthquake since 1690, are considered stalled. Centuries of energy are built up and ready to be released. When? Nobody knows.

Recent analyses suggest that in a worst-case scenario, the San Andreas would beget an earthquake ranking an 8.3 on the Richter scale, a logarithmic scale on which a 6.0 is ten times as powerful as a 5.0, a 7.0 ten times as powerful as a 6.0, and so forth. To put that in context, earthquakes under 2.5 are rarely felt. Earthquakes under 6.0 can cause some damage to buildings, but aren’t major events. Above that level things start to get interesting. The largest recorded quake in the United States was a 9.2 earthquake that hit Alaska in 1964.

“That would require the San Andreas to rupture wall to wall from its southern extremis to up to Cape Mendocino,” says Tom Jordan, the director of the Southern California Earthquake Center at The University of Southern California,. He explains that the creeping segment in the middle acts as a buffer, making the 8.3-magnitude earthquake much less plausible than some other options.

Even if the 8.3 earthquake never materializes, scientists worry that a rupture along the long-inactive southern segment could be devastating, compounded by the large population in the area. The 1989 Loma Prieta earthquake that shook San Francisco was only a 6.9, but it caused billions of dollars in damage injured over 3,000 people, and killed 63.

“The San Andreas lies close to the coastline where people live,” Jordan says. The valleys along the coast that proved so enticing to the settlers who founded cities like Los Angeles are large areas of sedimentary rock that could be hugely problematic in an earthquake.

“Even though L.A. is 30 miles from the San Andreas, it can still get very strong ground motion,” Jordan says. “The sediments shake like bowls of jelly.”

But even just a medium-bad scenario could be enough to kill hundreds and ruin the economy.

Researchers like Jordan are building up huge, incredibly detailed 3D maps of the geology near the San Andreas fault. These maps can be used to generate detailed assessments for almost any possible earthquake scenario that might happen along the fault.

In 2008, United States Geological Survey scientist Lucy Jones and colleagues published the ShakeOut scenario, a detailed report that looked at what could happen if a large (magnitude 7.8) earthquake occurred along the southern leg of the fault.

Simulated magnitude-8.0 earthquake.

Just like the 1906 earthquake in San Francisco, people living in the area would be without power and water for interminable lengths of time, and in the immediate aftermath, firefighters would not have access to water to fight the fires that would spring up in the wake of the disaster. And in California’s current drought, the fires after the earthquake could prove more devastating than the shaking itself.

Dodging A Bullet

Scientists may not be able to predict where and when a strike will hit, but the more they understand what could happen, the more they can help plan for any event. Last winter, Los Angeles Mayor Eric Garcetti announced a plan called Resilience By Design, that tries to address the huge risk facing the city if there was an earthquake along the San Andreas.

“It is highly unlikely we’ll make a century [without a large earthquake]” said Jones, who also headed up the Resilience by Design group. Reinforcing the city’s lifelines, like roads and utilities, is a huge priority.

Fortunately, California has a precedent to the north.

In 2002, the Denali fault in Alaska slipped and caused an earthquake with a magnitude of 7.9, the largest inland earthquake recorded in the country in 150 years. And running right across that fault was the Trans-Alaska Pipeline, an 800-mile long piece of infrastructure that carries 550,000 barrels of crude across near-pristine tundra every day.

“It was the biggest ecological disaster that never happened.” Jones said.

The pipeline was built to accommodate the movement of the earth, so that even though the earth slid by up to 18 feet in the 2002 earthquake, the pipeline didn’t break, averting a serious oil spill. To avoid rupturing, the engineers designed the above-ground portion of the pipeline in an intentional zig-zag pattern instead of a straight line, giving the pipeline flexibility. The pipeline itself can also slide. Instead of being anchored in the permafrost, part of the pipeline sit on Teflon-coated ‘shoes’ which rest on huge steel beams that sit perpendicular to the pipeline. In the event of shaking, segments of the pipe can slide on the beams like train cars on rails, without breaking.

Denali Pipeline. The zig-zag pattern allows it to flex and move without breaking.

The Next Quake

In California, water pipes and electrical lines could be built or retrofitted with similar flexibility. Researchers are even working on building earthquake-resistant houses that can slide back and forth on instead of crumbling. Unlike traditional homes, which sit on a foundation, these earthquake-resistant homes sit on sliders made out of steel, that, just like the Trans-Alaska Pipeline, can slide over the shaking ground instead of breaking.

The internet of everything has a role to play here too. In the future, networks of devices scattered across the southern California landscape could monitor an earthquake as it starts. This seismic network could send out an alert as the earthquake propagates through the earth, giving utilities precious seconds of warning to shut off valves in pipes along the fault, shut off power to prevent damage, and even send an alert to operating rooms, allowing a surgeon to remove her scalpel from a patient before the shaking even begins.

Scientists already have a seismic network in California, but more seismic sensors and technical development are needed to get the fledgling network to the next level. Unfortunately, those developments require money, and getting enough funding to build the next system has been elusive.

The cost for a truly robust alert system is estimated at $80 million for California alone, and $120 million for the whole West Coast. But funding is sparse. Earlier this year, President Obama pledged $5 million. The first sensors are already being used by San Francisco’s mass transit system to slow down trains in the event of an earthquake.

To see what the future of California might look like, one only has to glance west towards Japan, where even their fastest trains come to a halt at the first sign of an earthquake, elevators allow people to disembark, and people get warnings on radio, TV, and cell phones.

Similar techniques could be employed near Los Angeles, Jones says, making the city ready to bounce back from even the worst earthquake that the San Andreas can throw at the city.

Ralph Waldo Emerson once said that “we learn geology the morning after the earthquake.” Fortunately for Los Angeles, plenty of people, from geologists to city and emergency planners, have no intention of waiting that long.

California Earthquakes Since 1900

Earthquakes in California cluster along its fault lines. Here are the epicenters of the state’s strongest 20th-century quakes. Even though truly massive quakes on the San Andreas are rare, it’s still a very active line, with many dots appearing along its length.

Earthquakes in California cluster along its fault lines. Here are the epicenters of the state’s strongest 20th-century quakes. Even though truly massive quakes on the San Andreas are rare, it’s still a very active line, with many dots appearing along its length.

The animation includes all California earthquakes between January 1900 and July 2015 with magnitude 4.2 or greater. The circle size represents earthquake magnitude while color represents date, with the earliest quakes in yellow and the most recent in red. The San Andreas appears as a red line running down the left side of the state. Better seismic sensors detect weaker earthquakes, so milder quakes don’t appear in the early years of the animation.

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

See the full article here .

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From COSMOS: ” ‘Locked, loaded and ready to roll’: San Andreas fault danger zones”

COSMOS

05 December 2016
Kate Ravilious

The Carrizo Plain in eastern San Luis Obispo County, California, contains perhaps the most strikingly graphic portion of the San Andreas fault. Roger Ressmeyer / Corbis / VCG

A series of small earthquakes up to magnitude 4 started popping off right next to the San Andreas fault at the end of September, giving Californian seismologists the jitters.

This swarm of more than 200 mini-quakes radiated from faults under the Salton Sea, right down at the southern end of the San Andreas fault.

And although the small quakes only released tiny amounts of energy, the fear was that this fidgeting could be enough to trigger an earthquake on the big fault. “Any time there is significant seismic activity in the vicinity of the San Andreas fault, we seismologists get nervous,” said Thomas Jordan, director of the Southern California Earthquake Centre in Los Angeles.

Because despite a plethora of sensitive instruments, satellite measurements and powerful computer models, no-one can predict when the next big one will rattle the Golden State.

Cosmos magazine / Getty Images

Slicing through 1,300 kilometres of Californian landscape from Cape Mendocino in the north-west all the way to the Mexican border in the south-east, the San Andreas fault makes itself known.

Rivers and mountain ranges – and even fences and roads – are offset by the horizontal movement of this “transform” fault, where the Pacific Ocean plate to the west meets the North American plate to the east. The fault moves an average of around 3.5 centimetres each year, but the movement comes in fits and starts. Large earthquakes doing most of the work, punctuating long periods of building pressure.

The fault divides roughly into three segments, each of which tends to produce a big quake every 150 to 200 years.

The last time the northern segment (from Cape Mendocino to Juan Bautista, south of San Francisco) released stress was during the devastating magnitude-7.8 San Francisco Bay quake in 1906, which killed thousands and destroyed around 80% of San Francisco.

Meanwhile, the central section, from Parkfield to San Bernardino, has been quiet for longer still, with its last significant quake in 1857, when a magnitude-7.9 erupted underneath Fort Tejon.

But most worrying of all is the southern portion (from San Bernardino southwards through the Coachella Valley), which last ruptured in the late 1600s. With more than 300 years of accumulated strain, it is this segment that seismologists view as the most hazardous.

“It looks like it is locked, loaded and ready to roll,” Jordan announced at the National Earthquake Conference in Long Beach in May 2016.

This explains why the recent earthquake swarm was considered serious enough for the United States Geological Survey to issue a statement: that the risk of a magnitude-7 quake in Southern California was temporarily elevated from a one in 10,000 chance to as much as a one in one in 100.

“We think that such swarms of small earthquakes indicate either that fluids are moving through the crust or that faults have started to slip slowly,” says Roland Bürgmann, a seismologist at University of California, Berkeley. “There is a precedent for such events having the potential to trigger earthquakes.”

And last year he showed it’s not just the San Andreas fault we need to worry about. Working near the northernmost segment of the fault, Bürgmann and his colleagues used satellite measurements and data from instruments buried deep underground to map out the underground shape of two smaller faults – the Hayward and Calaveras – which veer off to the east of San Francisco. These two smaller faults, which are known to be capable of producing their own sizeable earthquakes (up to magnitude 7), turned out to be connected [Geophysical Research Letters]. Until now, sediments smothered the link.

And in October, another study published in Science Advances showed that the Hayward fault is connected by a similarly direct link to a third fault to the north – the Rodgers Creek fault.

“This opens up the possibility of an earthquake that could rupture through this connection, covering a distance of up to 160 kilometres and producing an earthquake with magnitude much greater than 7,” Bürgmann says.

“It doesn’t mean that this will happen, but it is a scenario we shouldn’t rule out.”

Down the other end of the San Andreas fault, Julian Lozos from the California State University in Los Angeles has been testing various earthquake scenarios using a detailed computer model of the fault system.

He too has shown that a seemingly minor side-fault – known as the San Jacinto – is more of a worry than previously thought. In this case, the San Jacinto falls short of intersecting the San Andreas by around 1.5 kilometres, but Lozos’ model suggests large earthquakes can leap this gap.

“We already know that the San Andreas is capable of producing a magnitude-7.5 on its own, but the new possibility of a joint rupture with the San Jacinto means there are now more ways of making a magnitude-7.5,” says Lozos, whose findings were published in Science Advances in March this year.

By feeding historic earthquake data into his model, he showed that the magnitude-7.5 earthquake that shook the region on 8 December 1812 is best explained by a quake that started on the San Jacinto but hopped across onto the San Andreas and proceeded to rupture around 50 kilometres north and southwards.

If such a quake were to strike again today, the consequences could be devastating, depending on the rupture direction.

“The shaking is stronger in the direction of unzipping,” explains Lozos. And in this case, the big worry is a northward unzipping, which would funnel energy into the Los Angeles basin.

In 2008, the United States Geological Survey produced the ShakeOut Scenario: a model of a magnitude-7.8 earthquake, with between two and seven metres of slippage, on the southern portion of the San Andreas fault.

Modern buildings could generally withstand the quake, thanks to strict modern building codes, but older buildings and any buildings straddling the fault would likely be severely damaged.

But the greatest concern was the effect the movement would have on infrastructure – slicing through 966 roads, 90 fibre optic cables, 39 gas pipes and 141 power lines. Smashed gas and water mains would enable fires to rage, causing more damage than the initial shaking of the quake.

The overall death toll was estimated at 1,800, and the long-term consequences expected to be severe, with people living with a sequence of powerful aftershocks, and a long slow road to recovery. Simply repairing water mains, for instance, could take up to six months.

In this simulation, the city of Los Angeles doesn’t take a direct hit, since it lies some way from the San Andreas fault. But there is another scenario which keeps Jordan awake at night.

Back in 1994, a magnitude-6.7 “Northridge” earthquake struck the San Fernando valley, about 30 kilometres north-west of downtown Los Angeles, killing 57 people and causing between US$13 and $40 billion of damage – the costliest natural disaster in the US at that time.

Collapsed overpass on Highway 10 in the Northridge/Reseda area – a result of the 1994 earthquake. Visions of America / UIG / Getty Images

“This was a complete eye-opener for us all, as it occurred on a blind thrust fault that no-one knew existed,” says Jordan. Geologists have since worked overtime to discover these hidden faults, and in 1999 they found that Los Angeles itself sits atop the Puente Hills fault – a steeply angled “thrust” fault that is thought to produce earthquakes of greater than magnitude 7 every few thousand years.

“We are more likely to see a large earthquake on the San Andreas fault in the short to medium term, but we still have to accept that this thrust fault could move at any time, and because of its location underneath Los Angeles, the consequences would be very severe,” says Jordan.

Much of Los Angeles is underlain by soft sediments, which wobble furiously when rattled by a quake, and it is these areas that would likely sustain the most damage.

Thankfully, the Los Angeles city council is taking the risk seriously. Models such as ShakeOut Scenario motivated the city to produce emergency plans and retrofit dangerous buildings. Seismologists such as Jordan and Lozos live in Los Angeles, but confess that the risk does affect their everyday life.

“It crosses my mind when I drive over the freeway that collapsed in 1994, or when I’m deciding what kind of house to live in,” says Lozos. “Others mock me for worrying, but as a seismologist, I know that the longer you go without a quake the greater the chances of a quake are.”

Meanwhile, Jordan, who lives in a house underlain by solid granite bedrock, justifies his decision to live in this precarious part of the world: “If you want to hunt elephants, you have to go to elephant country.”

See the full article here .

You can help catch earthquakes.

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

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From Science Alert: “A SECOND fault line running parallel to San Andreas has just been identified”

Science Alert

And it might be holding everything together.

5 OCT 2016
BEC CREW

The San Andreas Fault. Credit: US Geological Survey

Just days after a cluster of more than 200 small earthquakes shook the Salton Sea area of Southern California, scientists have found evidence of a second fault line that runs parallel to the massive San Andreas Fault – one of the state’s most dangerous fault lines.

The new fault appears to run right through the 56-km-long Salton Sea in the Colorado Desert, to the west of the San Andreas Fault. Now that we know it’s there, seismologists will be forced to reassess earthquake risk models for the greater Los Angeles area.

“This previously unidentified fault represents a new hazard to the region and holds significant implications for fault models … and, consequently, models of ground-motion prediction and southern San Andreas Fault rupture scenarios,” the team from the Scripps Institution of Oceanography and the Nevada Seismological Laboratory reports.

Now known as the Salton Trough Fault, the newly mapped fault has been hidden for all this time because it’s submerged beneath the Salton Sea – a vast, salty rift lake that formed as a result of all the tectonic activity in the area.

The team had to use an array of instruments, including multi-channel seismic data, ocean-bottom seismometers, and a surveying method called light detection and ranging (LiDAR), to precisely map fault inside several sediment layers both in and surrounding the lakebed.

“The location of the fault in the eastern Salton Sea has made imaging it difficult, and there is no associated small seismic events, which is why the fault was not detected earlier,” says Scripps geologist Neal Driscoll.

Oddly enough, the fact that we now know there’s an extra fault line running parallel to the San Andreas Fault doesn’t necessarily mean the area is more prone to earthquakes than we originally thought.

It might actually solve the mystery of why the region has been experiencing LESS earthquakes than expected.

As the team explains, recent research has revealed that the region has experienced magnitude-7 earthquakes roughly every 175 to 200 years for the last 1,000 years.

But that’s not been the case more recently. In fact, a major rupture on the southern portion of the San Andreas Fault has not occurred in the last 300 years, and researchers think the region is long overdue for a major quake.

Now they have to figure out what role the Salton Trough Fault could have played in all that.

“The extended nature of time since the most recent earthquake on the Southern San Andreas has been puzzling to the earth sciences community,” said one of the Nevada team, seismologist Graham Kent.

“Based on the deformation patterns, this new fault has accommodated some of the strain from the larger San Andreas system, so without having a record of past earthquakes from this new fault, it’s really difficult to determine whether this fault interacts with the southern San Andreas Fault at depth or in time.”

A map of the new fault line, STF. Credit: Sahakian et. al.

On Monday morning, ominous rumblings started to emanate from deep underneath the Salton Sea, and then a ‘swarm’ of small earthquakes – three measuring above magnitude 4 – ruptured at the nearby Bombay Beach.

The ruptures continued for roughly 24 hours, with more than 200 small earthquakes having been recorded in the area.

These small earthquakes – or temblors – were not very severe, but this is just the third time since records began in 1932 that the area has experienced such an event. And this one had more earthquakes than both the 2001 and 2009 events.

The event caused the US Geological Survey to increase the estimated risk of a magnitude 7 or greater earthquake in the next week from to between 1 in 3,000 and 1 in 100. To put that in perspective, without any quake swarms, the average risk for the area sits at around 1 in 6,000.

Fortunately, the increased risk now appears to have passed, and according to the Los Angeles Times, California governor’s Office of Emergency Service just announced that the earthquake advisory period is now officially over.

Of course, for those living in the area, it’s cold comfort, because the southern San Andreas Fault is still “locked, loaded, and ready to go”. Let’s hope the discovery of the Salton Trough Fault will make it easier for seismologists to at least predict when that will happen.

The research has been published in the Bulletin of the Seismological Society of America.

See the full article here .

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From GIZMODO: “Massive Earthquake Along the San Andreas Fault Is Disturbingly Imminent”

GIZMODO

9.30.16
George Dvorsky

The USGS estimates a 1 in 100 chance of the San Andreas Fault rupturing between now and October 4. (Image: SanAndreasFault.org)

A series of quakes under the Salton Sea may be a signal that the San Andreas Fault is on the verge of buckling. For the next few days, the risk of a major earthquake along the fault is as high as 1 in 100. Which, holy crap.

The United States Geological Survey has been tracking a series of earthquakes near Bombay Beach, California. This “earthquake swarm” is happening under the Salton Sea, and over 140 events have been recorded since Monday September 26. The quakes range from 1.4 to 4.3 in magnitude, and are occurring at depths between 2.5 to 5.5 miles (4 to 9 km).

Quakes recorded under the Salton Sea on September 27, 2016. (Image: USGS)

For seismologists, these quakes could represent some seriously bad news. The swarm is located near a set of cross-faults that are connected to the southernmost end of the San Andreas Fault. Troublingly, some of these cross-faults could be adding stress to the San Andreas Fault when they shift and grind deep underground. Given this region’s history of major earthquakes, it’s got some people a bit nervous.

Calculations show that from now until October 4, the chance of a magnitude 7 or greater earthquake happening along the Southern San Andreas Fault is as high as 1 in 100, and as low as 1 in 3,000. On the plus side, the likelihood of it happening decreases with each passing day. These estimates are based on models developed to assess the probabilities of earthquakes and aftershocks in California.

“Swarm-like activity in this region has occurred in the past, so this week’s activity, in and of itself, is not necessarily cause for alarm,” cautions the USGS.

That being said, this is only the third swarm that has been recorded in this area since sensors were installed in 1932, and it’s much worse than the ones recorded in 2001 and 2009. This particular stretch of the San Andreas Fault hasn’t ruptured since 1680, and given that big quakes in this area happen about once every 150 to 200 years, this fault line is considerably overdue.

A big fear is that the rupturing of the southern portion of the San Andreas fault could cause a domino effect along the entire stretch, cracking the fault from Imperial County through to Los Angeles County. Another possibility is that the Salton Sea swarm could cause the nearby San Jacinto fault system to rupture, which would in turn trigger the collapse of the San Andreas Fault.

Should the Big One hit, it won’t be pretty. Models predict a quake across the southern half of California with a magnitude around 7.8. Such a quake would cause an estimated 1,800 deaths, 50,000 injuries, and over $200 billion in damage.

But as the USGS researchers point out, this is far from an inevitability. The swarm under the Salton Sea may subside, or fail to influence the gigantic fault nearby. Moreover, the estimates provided by the scientists are exactly that—estimates. The science of earthquake prediction is still very much in its infancy, and these models are very likely crunching away with insufficient data. No need to panic just yet.

See the full article here .

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“We come from the future.”

From Eos: “Tiny, Deep Quakes Increase on San Andreas as Tides Tug on Fault”

Eos

26 July 2016
Amy Coombs

Aerial view of the San Andreas Fault at the Carrizo Plain. The number of deep, slow-moving earthquakes that rumble near here rises and falls with each tidal cycle. Credit: Ikluft

Much like ocean waters rise and fall during daily tidal cycles, the Earth’s crust bows outward, then relaxes every day, pulled by the Moon. The ocean also rises and falls on 2-week tidal cycles when the pull of the Sun reinforces the tug of the Moon, a phenomenon also observed in Earth’s crust.

According to new measurements, this bulging of the crust every 2 weeks cyclically increases the numbers of small earthquakes that take place deep in the San Andreas Fault. These temblors occur between 15 and 30 kilometers underground and release too little energy too slowly to be felt by anyone on the surface.

What’s more, the pattern of these slow-moving earthquakes reveals something unexpected—that they “are most common during the week when tides are growing rather when tides are the biggest,” said Nicholas van der Elst, a geophysicist at the Earthquake Science Center at the U.S. Geological Survey (USGS) in Pasadena, Calif. Van der Elst and his team published the findings on 18 July in the Proceedings of the National Academy of Sciences of the United States of America.

The new study shows no connections between these “low-frequency earthquakes,” as researchers refer to them, and the sudden, ground-shaking earthquakes that typically originate much closer to the surface and can cause widespread destruction and death. However, their very presence reveals information about the deep mechanics of the fault.

Recording Fault Slippage

Despite their “low-frequency” label, these earthquakes are detected more frequently than any other class of quakes near Parkfield, Calif.—the section of the San Andreas Fault observed in the study. More than a thousand of these low-level seismic slips register every day at Parkfield, but because of their depth and low magnitudes (<1) people can’t feel them. Scientists refer to them as “low frequency” because they are characterized by slow seismic waves of compression and expansion analogous to low-frequency (i.e., low-pitch) sounds.

Seismologists from the USGS and Northern California Seismic Network recorded these slow quakes near Parkfield with sensitive seismic equipment placed in deep holes. They set out to record small tremors of slightly greater magnitude in areas where the fault is already known to churn with deep activity.

The low-frequency quakes became apparent only when scientists used algorithms to extract weak signals from background noise. By contrast, in the relatively shallow areas where the “big one” might hit, the fault moves far less, allowing stress to build up until a large quake occurs, said van der Elst.

Quake Tally Rises as Biweekly Tide Waxes

Finding that the crustal tide affects deep, little quakes isn’t entirely new. Scientists previously looked into the frequency of earthquakes during daily Earth tides, which sometimes lift rock by a few centimeters over a 12-hour cycle akin to the timing of ocean tides.

Although those past findings proved inconclusive in the shallow regions of the fault where bigger earthquakes strike, results showed that deep, low-frequency earthquakes take place 50% more often when the daily crustal tides hit their maximum heights.

To learn if the total number of small, deep earthquakes rises and falls also with the fortnightly tide, van der Elst and his colleagues returned to data from Parkfield to analyze 81,000 low-frequency quakes and found that their abundance correlated statistically with the 2-week tidal pattern.

It turns out that low-frequency earthquakes are 10% more common during weeks when the biweekly Earth tide is growing. Van der Elst and his team identified two time periods each month when the low-level, deep quakes were most common, and both correlated with the two waxing cycles of the fortnightly tide, when tension builds in the fault, rather than the tidal peaks, when tension is greatest.

The scientists suggest why the number of quakes doesn’t surge again during the waning phase even though the tidal contribution to stress is just as large in that period: According to van der Elst, the boost in earthquake numbers during the waxing period likely relieves fault tension so that little is left to be released during waning. However, during the lull between waxing periods, the movement of the fault’s adjoining tectonic plates builds stress up again. Then, “when the tide begins to rise,” said van der Elst, “the fault is that much closer to failure and produces a bigger crop of low-frequency earthquakes early on.”

Peering into a Fault’s Depths

Although the results “are not directly relevant to forecasting damaging earthquakes, [they] open a new window to deep faulting, which remains mysterious in many ways,” commented John Vidale of the University of Washington in Seattle. Vidale did not participate in the study.

The results may provide valuable insights into the working of the deep fault, according to van der Elst. For example, only a weak fault would respond to the small amount of stress caused by tides, and the sensitivity to tides at deep levels might indicate the presence of pressurized fluids that lubricate the fault far below ground, he suggested.

Also, “variations in fault response over the fortnightly cycle tells you something about how long it takes for the fault to reaccumulate stress after an episode of low-frequency earthquakes,” said van der Elst. Future studies will explore these and other mechanisms.

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 Science Alert: “Scientist says the San Andreas fault is ‘locked, loaded, and ready to roll’ “

Science Alert

5 MAY 2016
FIONA MACDONALD

That can’t be good.

Southern California Earthquake Centre

California’s San Andreas fault has been quiet for far too long and is overdue for a major earthquake, a leading geoscientist has announced. In a conference this week, the state was warned to prepare for a potential earthquake as strong as magnitude 8.0.

“The springs on the San Andreas system have been wound very, very tight. And the southern San Andreas fault, in particular, looks like it’s locked, loaded and ready to go,” said Thomas Jordan, director of the Southern California Earthquake Centre.

Jordan gave his warning in the keynote talk of the annual National Earthquake Conference in Long Beach, the Los Angeles Times reports.

Here’s why he’s so worried: research has shown that the Pacific plate is moving northwest relative to the North American plate at a rate of around 5 metres (16 feet) every 100 years – and that’s building up a whole lot of tension along the San Andreas fault line that needs to be relieved regularly.

But the last time southern California experienced a major shake-up was in 1857, when a magnitude 7.9 quake rupture almost 300 km (185 miles) between Monterey County and the San Gabriel Mountains.

Further south, areas of the fault line have been quiet even longer, with San Bernardino county not moving substantially since 1812, and the region near the Salton Sea remaining still since the late 1600s.

All of this means that there’s a lot of tension underneath California right now. Last year, Jordan’s team found there’s a 7 percent chance the state will experience a magnitude 8.0 quake in the next three decades.

And that’s a big problem. Back in 2008, a US Geological Survey report* found that a magnitude 7.8 earthquake on the southern San Andreas fault could cause more than 1,800 deaths, 50,000 injuries, US$200 billion in damage, and long-lasting infrastructure disruptions – such as six months of compromised sewer systems and ongoing wildfires.

Even though Los Angeles isn’t on the San Andreas fault line, simulations by the Southern California Earthquake Centre show that the shaking would quickly spread there:

Access mp4 video here .

According to their modelling, that size earthquake could cause shaking for nearly 2 minutes, said Jordan, with the strongest activity in the Coachella Valley, Inland Empire and Antelope Valley.

The reason Los Angeles is at so much risk is because it’s built over a sedimentary basin, and the seismic waves spread and get trapped there to cause more extreme and longer-lasting shaking. As you can see in the magnitude 8.0 simulation:

Access mp4 video here .

While Jordan praised recent initiatives to earthquake retrofit buildings in LA, he warned that the rest of the state needs to get ready for the next big one, by making residents more aware of ways to stay safe during an earthquake and when and how to evacuate.

“We are fortunate that seismic activity in California has been relatively low over the past century,” Jordan explained last year. “But we know that tectonic forces are continually tightening the springs of the San Andreas fault system, making big quakes inevitable.”

*Science paper
The ShakeOut Scenario

See the full article here .

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