From UCR: “Better Understanding Post-Earthquake Fault Movement”

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UC Riverside

July 18, 2016
Sean Nealon
Tel: (951) 827-1287
sean.nealon@ucr.edu

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Schematic summary of research findings showing the sequence of slip behavior.

Preparation and good timing enabled Gareth Funning and a team of researchers to collect a unique data set following the 2014 South Napa earthquake that showed different parts of the fault, sometimes only a few kilometers apart, moved at different speeds and at different times.

Aided by GPS measurements made just weeks before the earthquake and data from a new radar satellite, the team found post-earthquake fault movement, known as afterslip, was concentrated in areas of loosely packed sediment. Areas where the fault passed through bedrock tended to slip more during the actual earthquake.

Sections of Highway 12, which runs through the earthquake zone, were broken during the initial 6.0 magnitude earthquake and were further damaged in the coming days due to afterslip. In some areas the afterslip damage exceeded the initial damage from the earthquake.

“No one has seen variability in afterslip like we saw,” said Funning, an associate professor of earth sciences at the University of California, Riverside. “This helps us address a big question: Can we use geology as a proxy for fault behavior? Our findings suggest there is a relationship between those two things.”

The findings could have significant implications for earthquake hazard models, and also for planning earthquake response. If geological information can give a guide to the likely extent of future earthquakes, better forecasts of earthquake damage will be possible. And if areas likely to experience afterslip can be identified in advance, it can be taken into account when building or repairing infrastructure that crosses those faults.

California, in particular the Hayward and Calaveras Faults, which run along the east side of the San Francisco Bay, seems more susceptible to afterslip than other earthquake-prone regions throughout the world, Funning said.

The findings on the South Napa earthquake were recently published in paper, Spatial variations in fault friction related to lithology from rupture and afterslip of the 2014 South Napa, California, earthquake, in the journal Geophysical Research Letters.

Funning’s work in the region just north of San Francisco dates back to 2006, when he was a post-doctoral researcher at UC Berkeley and noticed the area wasn’t that well studied, at least compared to the central Bay Area.

He continued the research after he was hired at UC Riverside and received funding from the United States Geological Survey to conduct surveys using GPS sensors in earthquake prone areas throughout Marin, Napa, Sonoma, Mendocino and Lake counties.

He began the most recent survey in July 2014. When the South Napa earthquake struck on Aug. 24, 2014, he and three other researchers were in Upper Lake, CA in Lake County, about 70 miles north of the earthquake’s epicenter, making additional measurements.

The earthquake occurred at 3:20 a.m. By noon, Funning and the other researchers, Michael Floyd (a former post-doctoral researcher with Funning who is now a research scientist at the Massachusetts Institute of Technology), Jerlyn Swiatlowski (a graduate student working with Funning) and Kathryn Materna (a graduate student at UC Berkeley), had deployed additional GPS sensors in the earthquake zone in locations that they had, fortuitously, measured just seven weeks earlier.

In total, there were more than 20 GPS sensors set up by Funning’s team and scientists from the United States Geological Survey. They left the equipment out for four weeks following the earthquake.

They then combined the GPS sensor data with remote sensing data. The South Napa earthquake was the first major earthquake to be imaged by Sentinel-1A, a European radar imaging satellite launched in 2014 that provides higher resolution information than was previously available.

In addition to Funning, authors of the paper are: Floyd, Richard J. Walters, John R. Elliott, Jerry L. Svarc, Jessica R. Murray, Andy J. Hooper, Yngvar Larsen, Petar Marinkovic, Roland Bürgmann, Ingrid A. Johanson and Tim J. Wright.

See the full article here .

Meet The Quake-Catcher Network

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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
QCN Quake Catcher Network map

Please help promote STEM in your local schools.

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Stem Education Coalition

UC Riverside Campus

The University of California, Riverside is one of 10 universities within the prestigious University of California system, and the only UC located in Inland Southern California.

Widely recognized as one of the most ethnically diverse research universities in the nation, UCR’s current enrollment is more than 21,000 students, with a goal of 25,000 students by 2020. The campus is in the midst of a tremendous growth spurt with new and remodeled facilities coming on-line on a regular basis.

We are located approximately 50 miles east of downtown Los Angeles. UCR is also within easy driving distance of dozens of major cultural and recreational sites, as well as desert, mountain and coastal destinations.