From Stanford: “Stanford researchers find similar characteristics in human-induced and natural earthquakes”

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August 2, 2017
Danielle Torrent Tucker

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A magnitude 5.6 earthquake likely induced by injection into deep disposal wells in the Wilzetta North field caused house damage in central Oklahoma on Nov. 6, 2011. Research conducted by Stanford scientists shows human-induced and naturally occurring earthquakes in the central U.S. share the same shaking potential and can thus cause similar damage. (Image credit: Brian Sherrod, USGS)

Whether an earthquake occurs naturally or as a result of unconventional oil and gas recovery, the destructive power is the same, according to a new study appearing in Science Advances Aug. 2. The research concludes that human-induced and naturally occurring earthquakes in the central U.S. share the same shaking potential and can thus cause similar damage.

The finding contradicts previous observations suggesting that induced earthquakes exhibit weaker shaking than natural ones. The work could help scientists make predictions about future earthquakes and mitigate their potential damage.

“People have been debating the strength of induced earthquakes for decades – our study resolves this question,” said co-author William Ellsworth, a professor in the Geophysics Department at Stanford’s School of Earth, Energy & Environmental Sciences and co-director of the Stanford Center for Induced and Triggered Seismicity (SCITS). “Now we can begin to reduce our uncertainty about how hard induced earthquakes shake the ground, and that should lead to more accurate estimates of the risks these earthquakes pose to society going forward.”

Induced quakes

Earthquakes in the central U.S. have increased over the past 10 years due to the expansion of unconventional oil and gas operations that discard wastewater by injecting it into the ground. About 3 million people in Oklahoma and southern Kansas live with an increased risk of experiencing induced earthquakes.

“The stress that is released by the earthquakes is there already – by injecting water, you’re just speeding up the process,” said co-author Gregory Beroza, the Wayne Loel Professor in geophysics at Stanford Earth and co-director of SCITS. “This research sort of simplifies things, and shows that we can use our understanding of all earthquakes for more effective mitigation.”

Oklahoma experienced its largest seismic event in 2016 when three large earthquakes measuring greater than magnitude 5.0 caused significant damage to the area. Since the beginning of 2017, the number of earthquakes magnitude 3.0 and greater has fallen, according to the Oklahoma Geological Survey. That drop is partly due to new regulations to limit wastewater injection that came out of research into induced earthquakes.

Stress drop

To test the destructive power of an earthquake, researchers measured the force driving tectonic plates to slip, known as stress drop – measured by the difference between a fault’s stress before and after an earthquake. The team analyzed seismic data from 39 manmade and natural earthquakes ranging from magnitude 3.3 to 5.8 in the central U.S. and eastern North America. After accounting for factors such as the type of fault slip and earthquake depth, results show the stress drops of induced and natural earthquakes in the central U.S. share the same characteristics.

A second finding of the research shows that most earthquakes in the eastern U.S. and Canada exhibit stronger shaking potential because they occur on what’s known as reverse faults. These types of earthquakes are typically associated with mountain building and tend to exhibit more shaking than those that occur in the central U.S. and California. Although the risk for naturally occurring earthquakes is low, the large populations and fragile infrastructure in this region make it vulnerable when earthquakes do occur.

The team also analyzed how deep the earthquakes occur underground and concluded that as quakes occur deeper, the rocks become stronger and the stress drop, or force behind the earthquakes, becomes more powerful.

“Both of these conclusions give us new predictive tools to be able to forecast what the ground motions might be in future earthquakes,” Ellsworth said. “The depth of the quake is also going to be important, and that needs to be considered as people begin to revise these ground-motion models that describe how strong the shaking will be.”

The scientists said that the types of rocks being exploited by unconventional oil and gas recovery in the U.S. and Canada can be found all over the world, making the results of this study widely applicable.

“As we can learn better practices, we can help ensure that the hazards induced earthquakes pose can be reduced in other parts of the world as well,” Ellsworth said.

Additional authors include lead author Yihe Huang, a former postdoctoral researcher at Stanford and now an assistant professor at the University of Michigan. The study was supported by the Stanford Center for Induced and Triggered Seismicity.

Media Contacts

Gregory Beroza
School of Earth, Energy & Environmental Sciences:
(650) 723-4958 (office)
(650) 319-5636 (cell)
beroza@stanford.edu

Danielle T. Tucker,
School of Earth, Energy & Environmental Sciences:
(650) 497-9541,
dttucker@stanford.edu

See the full article here .

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

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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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