From Temblor: “M=5.0 Taiwan earthquake preceded by foreshock sequence”

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temblor

May 24, 2017
David Jacobson

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Southwestern Taiwan was hit by a M=5.0 earthquake today. This quake was preceded by a foreshock sequence that lasted approximately 33 hours. (Photo from: holidayssg.com)

At 9:10 p.m. local time today (24 May), a M=5.0 earthquake struck western Taiwan near the city of Chiayi, which is home to over 250,000 people. This earthquake was preceded by a foreshock sequence of five earthquakes beginning approximately 33 hours earlier. The foreshock sequence began with a M=3.6, and culminated with another M=3.6 five minutes before the M=5.0. Most earthquakes are not preceded by a foreshock sequence, making this quake rare. At this stage, there have been no reports of damage, and according to the Taiwan Central Weather Bureau, moderate shaking was felt in the M=5.0, which can rock buildings, and cause slight damage. So, close to the epicenter, it is possible that minor damage was sustained. Should we hear any reports of damage, we will update this post.

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This Temblor map shows the location of the M=5.0 earthquake in Taiwan. In addition to the location from EMSC, the USGS location is also shown to illustrate the discrepancy in the catalogs. One of the earthquakes in the foreshock sequence is also shown.

At this stage, there is a discrepancy between where the USGS and EMSC plot the location of today’s quake. The USGS has it in a stepover between the Chiuchiungkeng and Muchiliao-Liuchia faults, while EMSC has it just to the east of the Chiuchiungkeng Fault. The USGS location has been added to the Temblor map above so that this discrepancy can be seen (For any location outside the United States, Temblor shows EMSC data). The USGS has also produced a focal mechanism for this earthquake, which suggests both strike-slip and extensional components of slip, which is not consistent with the regional geology. Should a Taiwan focal mechanism come out, we will update this post.

Based on the location shown in Temblor, this earthquake was likely associated with the Chiuchiungkeng Fault, a thrust fault within the southwestern foothills of Taiwan. Because of high slip rates associated with this fault, the region is believed to have a high probability of experiencing a large magnitude earthquake. This is verified when we look at the Taiwan Earthquake Model (see below). This model shows the likelihood of strong ground motion in the next 50 years.

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This figure shows the Taiwan Earthquake Model with recent earthquakes shown. This colors in the figure represent ground motion values (g) with a 10% likelihood in 50 years. This is the spectral acceleration at a period of 0.3 seconds (3.3 Hz).

In addition to the Taiwan Earthquake Model, we can also consult the Global Earthquake Activity Rate (GEAR) model, to see what the likely earthquake magnitude is for this portion of Taiwan. This model, which uses global strain rates and seismicity since 1977, forecasts what the likely earthquake magnitude in your lifetime is for any location on earth. From the Temblor map below, one can see that a M=7.5 earthquake is likely in your lifetime. Such a quake could be devastating to the country, as a significant portion of the country’s agriculture is grown in southwestern Taiwan, and a large earthquake could damage valuable resources. Should anything change regarding the location or focal mechanism from today’s earthquake, we will update this post.

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This Temblor map shows the Global Earthquake Activity Rate (GEAR) model for Taiwan. What can be seen from this figure is that the area around today’s earthquake is susceptible to M=7.5+ quakes. Such an earthquake would be devastating to the area.

References
European-Mediterranean Seismological Centre (EMSC)
USGS
Taiwan Earthquake Model (TEM)
Taiwan Central Weather Bureau

See the full article here .

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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