From temblor: “M=4.1 Santa Barbara earthquake highlights local quake hazards”

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Last night’s M=4.1 earthquake in off the coast of Santa Barbara highlights a region with significant local quake hazards. (Photo from: santabarbaraca.com)

At 9:42 p.m. local time last night (16 May 2017), a M=4.1 earthquake struck offshore of Santa Barbara, California. The quake occurred at a depth of 2.3 km, and on the USGS website, over 1,400 people reported feeling the event. Having said that, Santa Barbara, 28 km from the epicenter, is home to nearly 100,000 people, and was exposed to weak shaking, so it is likely that many more people felt the earthquake. So far, there have been five recorded aftershocks to the north of the mainshock, ranging in size from M=1.8 to M=3.1. None of the earthquakes within the last nine hours was large enough to result in any damage, as only moderate shaking was experienced close to the epicenter of the M=4.1.

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Last night’s M=4.1 earthquake near Santa Barbara occurred just east of the epicenter of a M=6.8 quake in 1925. Additionally, the Red Mountain and Pitas Point faults to the east of the epicenter are capable of rupturing in M=7.7 quakes, which could generate a locally-sourced tsunami.

Based on the USGS focal mechanism, this was a purely compressional event with no component of strike-slip motion. While when most people think of faulting in California, they think of strike-slip movement, as is the case for the San Andreas and Hayward faults, in this part of the state, compression dominates, uplifting the Santa Ynez Mountains and the rest of the Transverse Ranges. The fault on which yesterday’s earthquake occurred was relatively steep (50-56°) and located approximately 3.5 km offshore. In this part of California, there are several small unnamed faults which are not believed to have been very seismically active in the last 700,000 years.

However, just to the east of last night’s quake is the south branch of the Red Mountain Fault Zone, a north-dipping thrust fault. While yearly slip along the Red Mountain Fault is low, 0.4-1.4 mm/yr, the Southern California Earthquake Data Center (SCEDC) believes that by itself, the fault is capable of M=6.0-6.8 earthquakes. Furthermore, some scientists believe that if the Red Mountain and Pitas Point Fault to the southeast were to rupture simultaneously, a M=7.7 earthquake could result, which could generate a locally-sourced tsunami, sending waves up to 30 feet high towards Santa Barbara (See figure below) (Ryan et al., 2015). Such events would cause significant damage to the region. This project was undertaken in 2012 to investigate the earthquake and tsunami hazards in Ventura Country, and as Southern California Earthquake Commission scientist David Oglesby said, “we all need to recognize that earthquake hazard doesn’t end at the water’s edge.”

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his figure from Ryan et al., 2015 shows peak tsunami amplitude from a M=7.7 earthquake on the Red Mountain and Pitas Point faults. What this illustrates is how a locally-sourced tsunami could generate 30 foot waves in Santa Barbara.

While the probability of a M=7.7 earthquake is likely very low, this part of Southern California is susceptible to moderately large quakes. By using the Global Earthquake Activity Rate (GEAR) model, we can determine what magnitude is most likely. This model, which is available in Temblor, uses global strain rates and seismicity since 1977 to determine the likely earthquake magnitude in your lifetime anywhere on earth. From the figure below, you can see that a M=6.25+ quake is likely to occur around Santa Barbara in your lifetime. The largest recorded quake in the area was a M=6.8 in 1925. Therefore, while yesterday’s quake was by no means significant, it allows us to highlight local earthquake hazards in Southern California.

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This Temblor map shows the Global Earthquake Activity Rate (GEAR) model for most of Southern California. This model uses global strain rates and seismicity since 1977 to forecast the likely earthquake magnitude in your lifetime anywhere on earth. What this map illustrates is that around Santa Barbara, a M=6.25+ earthquake is likely in your lifetime. To view the model, click the figure.

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
QCN Quake Catcher Network map

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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.

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