From temblor : “Tectonic mystery swirls as earthquake rocks California-Nevada border”

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From temblor

July 9, 2021
Ian Pierce-University of Oxford (UK)

On the afternoon of July 8, 2021, a magnitude-6.0 earthquake rocked much of central California and western Nevada. Intense shaking that lasted as long as 20 seconds was reported 80 miles (~130 kilometers) away in Reno, while the Bay Area, Central Valley, Southern California and even Las Vegas all shook as well. Reports of damages are slowly trickling in from many of the remote communities nearest the shaking and videos of car-sized boulders on a major highway have gone viral. Since the mainshock less than 24 hours ago (at the time of posting), more than 100 aftershocks above magnitude 2.5 have rocked the region. More than 25,600 people have reported feeling shaking to the U.S. Geological Survey’s (USGS) Did You Feel It? website. If you felt the mainshock or any of the aftershocks — or if you didn’t — report them.

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Map showing earthquakes that have rocked the Antelope Valley area, south of Lake Tahoe, since yesterday afternoon.

This earthquake originated in the seismically busy Central Walker Lane between Yosemite National Park in California and Carson City Nevada, in the southernmost part of Antelope Valley. In the last three years, four large earthquakes — greater than magnitude 6.0 — have struck the Walker Lane region. What’s driving all this seismic activity and what does it mean for the earthquake hazards far from the famed San Andreas Fault?

Busy Walker Lane

The Walker Lane is a diffuse zone of normal and strike-slip faults. It follows an approximately 60-mile (100-kilometer)-wide swath along the Eastern Sierras and California/Nevada border, reaching from Death Valley and the Garlock Fault in the south to north of the Honey Lake Valley region. The Walker Lane Fault system accommodates roughly 20 percent of the 2-inch (50-millimeter) per year right-lateral shear between the Pacific and North American Plates, while the remaining 80 percent is accommodated along the more well-known San Andreas Fault system.

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Annotated map showing locations of earthquakes greater than or equal to magnitude-6 in the Walker Lane region.

The Walker Lane has been getting much attention recently, and for good reason. In the last three years far more moderate earthquakes have occurred along the Walker Lane Fault system than any other single fault system in the western United States. This earthquake is the fourth event larger than magnitude-6.0 since the 2019 Ridgecrest Earthquake Sequence that included magnitude-6.4 and magnitude-7.1 earthquakes, and the 2020 magnitude-6.5 Monte Cristo Range earthquake. In 2021 alone, yesterday’s earthquake joins a series of several other widely felt events ranging from magnitude 4 to 5 near Lake Tahoe and the Northern Sierras.

Yet, the Walker Lane didn’t start popping off events in 2019. In 2016 the Nine Mile Ranch sequence produced three events of about magnitude-5.5 near Hawthorne, Nev., in less than an hour, following a similar sequence from 2011. In 2008, the Mogul sequence rocked Reno, Nev., with a magnitude-4.7 quake. The largest-known Walker Lane event was the 1872 magnitude-7.4 Owens Valley earthquake, which is roughly the maximum magnitude we expect of an earthquake along any single fault in this system.

Decades of paleoseismic and tectonic studies have revealed dozens of faults throughout the Walker Lane some with evidence of large prehistoric earthquakes that likely exceeded magnitude-7.0. For example, the most recent earthquake along the Genoa Fault near Carson City occurred about 450 years ago (Ramelli et al., 1999). The fault running beneath the west shore of Lake Tahoe most recently ruptured about 5,500 years ago (Pierce et al., 2017).

A tectonic mystery

Shifting attention to the tectonics of the Central Walker Lane where this most recent magnitude-6.0 event occurred, an unresolved tectonic mystery swirls. Using high accuracy stationary GPS stations, we can observe — in real time — the crest of the Sierra Nevada sliding northwest at a rate of about 0.3 inches (7 millimeters) per year relative to Fallon, Nev., shearing the region spanning Antelope, Smith, and Mason Valleys. Yet, geologically speaking, we cannot find sufficient strike-slip faulting to account for this observed shear.

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Overview of study area of Pierce et al., 2020, that includes Antelope Valley. Dark gray hillshades indicate lidar data. Red lines show mapped faults. Bold black lines show fault contacts between bedrock and alluvial sediments. Thin black lines come from the USGS Quaternary fault and fold database. Credit: Pierce et al., 2020, CC BY 4.0.

While a number of hypotheses have been proposed to explain this mismatch, we expect that future large earthquakes will show complex, transient and discontinuous deformation, as opposed to long-lasting fault strands that produce the fault scarps, large offsets of features in the landscape, and other geomorphologic features we would require to measure long-term faulting rates (Pierce et al., 2020). This more subtle, less dramatic style of deformation was witnessed in the 2020 Monte Cristo Range earthquake, as well as other earlier Walker Lane events. Other explanations for the missing measurable shear that we expect based on GPS data include clockwise rotations of basins and bounding normal faults, and obliquely slipping faults that bound the rangefronts of the mountains in this area.

The fault responsible for the July 8 magnitude-6.0 event produced a north-striking normal moment tensor — the beachball diagram seismologists use to determine both the orientation of a fault, and which way it moved. Normal faulting is consistent with the local patterns of faulting in Antelope Valley. In other words, the quake occurred on a north-striking fault that moves because of east-west directed extension, similar to what we would expect for the north-oriented Antelope Valley Fault that bounds the range. This fault does not have a significant oblique component, as one might expect if this range were accommodating right-lateral shear — the motion recorded by the San Andreas Fault, and the overall movement of the Walker Lane as recorded by GPS. This supports the conclusion of our 2020 paper suggesting this range does not exhibit oblique faulting — it is mostly normal.

Underappreciated hazards

All told, eastern California and western Nevada have much underappreciated earthquake hazards. While these hazards are well known to the earthquake science community, the public seems to view these moderate magnitude-5 to 6 events as “the big ones” when in reality, were the inevitable magnitude-7 event to occur in one of the rapidly developing communities of the region, the losses to life and property would be devastating.

Everyone living in this region should not only keep an earthquake kit and have a plan for inevitable forthcoming quakes, but they should also make sure their homes are prepared for earthquakes. There are a number of cost-effective measures that can be readily applied by homeowners to mitigate damage, like securing hot water heaters to walls and securing foundations. Finally, these moderate events should serve as a warning to our community leaders, and communities should encourage business owners to retrofit the relatively large number of unreinforced masonry structures in many of the historic districts of Reno, Carson Valley, Truckee, and Tahoe.

Remember, if you feel shaking, the U.S. Geological Survey says to drop, cover and hold on.

References:

Pierce, I. K., Wesnousky, S. G., & Owen, L. A. (2017). Terrestrial cosmogenic surface exposure dating of moraines at Lake Tahoe in the Sierra Nevada of California and slip rate estimate for the West Tahoe Fault. Geomorphology, 298, 63-71.

Pierce, I. K., Wesnousky, S. G., Owen, L. A., Bormann, J. M., Li, X., & Caffee, M. (2020). Accommodation of Plate Motion in an Incipient Strike‐Slip System: The Central Walker Lane. Tectonics, 40(2), e2019TC005612. doi: 10.1029/2019TC005612

Ramelli, A. R., Bell, J. W., Depolo, C. M., & Yount, J. C. (1999). Large-magnitude, late Holocene earthquakes on the Genoa fault, west-central Nevada and eastern California. Bulletin of the Seismological Society of America, 89(6), 1458-1472.

See the full article here .


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Earthquake Alert

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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.

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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

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

QuakeAlertUSA

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About Early Warning Labs, LLC

Early Warning Labs, LLC (EWL) is an Earthquake Early Warning technology developer and integrator located in Santa Monica, CA. EWL is partnered with industry leading GIS provider ESRI, Inc. and is collaborating with the US Government and university partners.

EWL is investing millions of dollars over the next 36 months to complete the final integration and delivery of Earthquake Early Warning to individual consumers, government entities, and commercial users.

EWL’s mission is to improve, expand, and lower the costs of the existing earthquake early warning systems.

EWL is developing a robust cloud server environment to handle low-cost mass distribution of these warnings. In addition, Early Warning Labs is researching and developing automated response standards and systems that allow public and private users to take pre-defined automated actions to protect lives and assets.

EWL has an existing beta R&D test system installed at one of the largest studios in Southern California. The goal of this system is to stress test EWL’s hardware, software, and alert signals while improving latency and reliability.

Earthquake Early Warning Introduction

The United States Geological Survey (USGS), in collaboration with state agencies, university partners, and private industry, is developing an earthquake early warning system (EEW) for the West Coast of the United States called ShakeAlert. The USGS Earthquake Hazards Program aims to mitigate earthquake losses in the United States. Citizens, first responders, and engineers rely on the USGS for accurate and timely information about where earthquakes occur, the ground shaking intensity in different locations, and the likelihood is of future significant ground shaking.

The ShakeAlert Earthquake Early Warning System recently entered its first phase of operations. The USGS working in partnership with the California Governor’s Office of Emergency Services (Cal OES) is now allowing for the testing of public alerting via apps, Wireless Emergency Alerts, and by other means throughout California.

ShakeAlert partners in Oregon and Washington are working with the USGS to test public alerting in those states sometime in 2020.

ShakeAlert has demonstrated the feasibility of earthquake early warning, from event detection to producing USGS issued ShakeAlerts ® and will continue to undergo testing and will improve over time. In particular, robust and reliable alert delivery pathways for automated actions are currently being developed and implemented by private industry partners for use in California, Oregon, and Washington.

Earthquake Early Warning Background

The objective of an earthquake early warning system is to rapidly detect the initiation of an earthquake, estimate the level of ground shaking intensity to be expected, and issue a warning before significant ground shaking starts. A network of seismic sensors detects the first energy to radiate from an earthquake, the P-wave energy, and the location and the magnitude of the earthquake is rapidly determined. Then, the anticipated ground shaking across the region to be affected is estimated. The system can provide warning before the S-wave arrives, which brings the strong shaking that usually causes most of the damage. Warnings will be distributed to local and state public emergency response officials, critical infrastructure, private businesses, and the public. EEW systems have been successfully implemented in Japan, Taiwan, Mexico, and other nations with varying degrees of sophistication and coverage.

Earthquake early warning can provide enough time to:

Instruct students and employees to take a protective action such as Drop, Cover, and Hold On
Initiate mass notification procedures
Open fire-house doors and notify local first responders
Slow and stop trains and taxiing planes
Install measures to prevent/limit additional cars from going on bridges, entering tunnels, and being on freeway overpasses before the shaking starts
Move people away from dangerous machines or chemicals in work environments
Shut down gas lines, water treatment plants, or nuclear reactors
Automatically shut down and isolate industrial systems

However, earthquake warning notifications must be transmitted without requiring human review and response action must be automated, as the total warning times are short depending on geographic distance and varying soil densities from the epicenter.