From temblor: “Significant damage following M=6.5 Chinese earthquake in area stressed by deadly 2008 Wenchuan quake”

1

temblor

August 10, 2017
David Jacobson

1
The M=6.5 earthquake in southwestern China occurred near Jiuzhai National Park, a popular tourist destination. So far, 19 people are known to have died as a result of this earthquake, and based on photos, there is significant damage. (Photo from: Flickr)

At 9:19 p.m. local time (8 Aug), a M=6.5 earthquake struck the Sichuan-Gansu border region in southwestern China. According to both the USGS and the European-Mediterranean Seismological Centre (EMSC), the quake occurred at a depth of 10 km in a mountainous region, near Jiuzhai National Park. This area is on the edge of the Tibetan Plateau and is extremely popular amongst tourists because of spectacular waterfalls and blue and green lakes. So far, 19 people are confirmed to have been killed by this event, and there is photo evidence of significant damage, which the USGS PAGER system estimates could be moderate to high near the epicenter, where very strong shaking was recorded.

2
This Temblor map shows the location of today’s M=6.5 earthquake in southwestern China. The quake is known to have killed at least 5 people, with dozens more injured.

Now that a few days have past, new photography which has come in from the area, illustrating that damage in nearby Jiuzhai National Park is significant (See below). This area brings in a significant amount of money to the area from tourism, and with the damage sustained, local officials are worried about the health of local businesses. At the time of the earthquake, local officials say there were 30,000 tourists in the area. The majority of these people have been evacuated and tourists are told to stay away.

3
Before and after images of Jiuzhai National Park in southwestern China. Many of these spectacular blue pools are separated by waterfalls and natural barriers which collapsed in the earthquake. (Photos from: China News (Left) and Getty Images (right))

4
The M=6.5 earthquake in southwestern China resulted in significant landslides which blocked and destroyed roads in addition to turning the blue pools in Jiuzhai National Park brown and murky. (Photo from: Shutterstock)

Based on the USGS focal mechanism, the M=6.5 earthquake was strike-slip with a thrust component. However, at this time we cannot be sure of the strike of the fault on which the quake occurred due to location inconsistencies between the USGS and EMSC and the numerous lineaments in the area. In this portion of the Tibetan Plateau, fault motion is dominated by left-lateral strike-slip faults, including the Altyn Tagh, Kunlun, and Haiyuan fault zones. Additionally, the location of the earthquake is approximately 280 km northwest of the epicenter of the 2008 M=7.9 Wenchuan earthquake which killed over 87,000 people. That earthquake occurred on the Longmenshan Fault, and was a thrust (compressional) event.

Even though the earthquake struck nearly 300 km from the Wenchuan earthquake, based on the figure below, one can see that this area saw a significant stress increase, which more than doubled the likelihood of a M=6+ earthquake. The side-by-side figures below show the observed rates of seismicity prior to the Wenchuan earthquake (left), and the forecasted seismicity in the 10 years following as a result of the stress imparted by the Wenchuan (The location of the August 8th quake is labeled with a star). This comparison shows that due to the Wenchuan earthquake, the area around today’s event went from having a 4% chance of experiencing a large quake, to 10%.

5
These side-by-side figures from Toda et. al., 2008 show the observed seismicity in the 10 years prior to the Wenchuan earthquake, as well as the 10 years after as a result of the stress imparted by the Wenchuan. The black stars represent the two largest (M>6) earthquakes since the Wenchuan earthquake, both of which occurred in areas which saw stress increases. What is evident from these figures is that as a result of the Wenchuan earthquake, the location of the August 8th event went from having a 4% chance of experiencing a M=6+ quake to a 10% chance. The green rectangle represents the 2008 Wenchuan fault rupture.

Based on the Global Earthquake Activity Rate (GEAR) model, which is available in Temblor, this earthquake can be seen as surprising. This model uses global strain rates and the last 40 years of seismicity to forecast the likely earthquake magnitude in your lifetime anywhere on earth. In the figure below, one can see that GEAR would forecast a M=5.75 earthquake in this region, significantly lower than the magnitude (M=6.5) of this event. This illustrates the importance of incorporating stress transfer into the likelihood of experiencing large earthquakes. GEAR does not, which is why it would see this quake as surprising.

6
This Temblor map shows the Global Earthquake Activity Rate (GEAR) model for southwestern China around the location of the August 8th M=6.5 earthquake. This model uses global strain rates and the last 40 years of seismicity to forecast the likely earthquake magnitude in your lifetime anywhere on earth. Based on the GEAR model, today’s earthquake should be seen as surprising, for it projects that only a M=5.75 quake is likely in your lifetime.

References
USGS
European-Mediterranean Seismological Centre
Shinji Toda, Jian Lin, Mustapha Meghraoui, and Ross S. Stein, 12 May 2008 M = 7.9 Wenchuan, China, earthquake calculated to increase failure stress and seismicity rate on three major fault systems, GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L17305, doi:10.1029/2008GL034903, 2008.

See the full article here .

Please help promote STEM in your local schools.

STEM Icon

Stem Education Coalition

You can help many citizen scientists in detecting earthquakes and getting the data to emergency services people in affected area.
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).

BOINCLarge

BOINC WallPaper

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

Earthquake country is beautiful and enticing

Almost everything we love about areas like the San Francisco bay area, the California Southland, Salt Lake City against the Wasatch range, Seattle on Puget Sound, and Portland, is brought to us by the faults. The faults have sculpted the ridges and valleys, and down-dropped the bays, and lifted the mountains which draw us to these western U.S. cities. So, we enjoy the fruits of the faults every day. That means we must learn to live with their occasional spoils: large but infrequent earthquakes. Becoming quake resilient is a small price to pay for living in such a great part of the world, and it is achievable at modest cost.

A personal solution to a global problem

Half of the world’s population lives near active faults, but most of us are unaware of this. You can learn if you are at risk and protect your home, land, and family.

Temblor enables everyone in the continental United States, and many parts of the world, to learn their seismic, landslide, tsunami, and flood hazard. We help you determine the best way to reduce the risk to your home with proactive solutions.

Earthquake maps, soil liquefaction, landslide zones, cost of earthquake damage

In our iPhone and Android and web app, Temblor estimates the likelihood of seismic shaking and home damage. We show how the damage and its costs can be decreased by buying or renting a seismically safe home or retrofitting an older home.

Please share Temblor with your friends and family to help them, and everyone, live well in earthquake country.

Temblor is free and ad-free, and is a 2017 recipient of a highly competitive Small Business Innovation Research (‘SBIR’) grant from the U.S. National Science Foundation.

ShakeAlert: Earthquake Early Warning

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 by 2018.

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, depending on the distance to the epicenter of the earthquake. For very large events like those expected on the San Andreas fault zone or the Cascadia subduction zone the warning time could be much longer because the affected area is much larger. ShakeAlert can give enough time to slow and stop 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 by 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” test 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. This “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

Advertisements