From temblor: “M=5.6 earthquake strikes Ecuador-Peru border”

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temblor

June 5, 2017
David Jacobson

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Guayaquil, Ecuador’s largest city experienced weak shaking from today’s M=5.6 earthquake to the south. (Photo from: nextstoplatinamerica.com)

At 4:34 p.m. local time, a M=5.6 earthquake struck Ecuador’s southern border with Peru. While this part of South America is not heavily populated, shaking was felt in the city of Guayaquil, which is home to 3.5 million people. According to the USGS, only light shaking was felt close to the epicenter, while weak shaking was felt in Guayaquil. The USGS also estimates that damage from this quake should remain minimal, and that fatalities are unlikely. Based on reports coming in from South America, two people are reported to have been injured, and minor damage has been noted. Should more information come in, we will update this post.

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This Temblor map shows the location of today’s M=5.6 earthquake near the Ecuador-Peru border. Also shown in this figure is the city of Guayaquil, which is Ecuador’s largest city. This city of 3.5 million people experienced weak shaking in the earthquake.

Based on the reported depth from both the USGS (52 km) and the EMSC (60 km), and the thrust focal mechanism, this earthquake likely occurred on the subducting slab where the Nazca Plate slides beneath the South American. By examining the Slab 1.0 model from the USGS’ Gavin Hayes (which is also visible in Temblor as ‘Megathrust Zones’), the subducting slab should be between 50 and 60 km depth in the location of today’s earthquake. Therefore, a minor slip event on the subduction zone is the likely cause of the quake.

While this was a small earthquake, this location, and nearly the entire western margin of South America is prone to large, damaging earthquakes. The Peru-Chile Trench, which marks where the Nazca Plate begins subducting beneath the South American Plate, lies only 20-60 km offshore. It should also be pointed out that even though western South America is at risk of large earthquakes, the behavior of the subducting slab varies greatly. In much of southern Peru, northern Chile, and southern Chile, the slab dips at angles of 25° to 30°. However, in southern Ecuador, and central Chile, the slab dips at 10° or less. In these areas of “flat-slab” subduction, crustal earthquakes within the overlying South American Plate are common. In fact, in 1970, a M=7.2 earthquake just to the west of today’s quake killed at least 80 people and caused liquefaction. This quake occurred at a depth of 25 km, suggesting it was likely an upper crustal event.

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This Temblor map shows recent large magnitude subduction zone earthquakes around the location of today’s M=5.6 quake. What is evident is that there have been earthquakes several hundred kilometers to the north and south of today’s event, but none in southern Ecuador. This could mean that the area has built up a significant amount of stress, which could be released in a large subduction zone earthquake, or that the geometry of the subduction zone prevents large events from happening.

Based on the Global Earthquake Activity Rate (GEAR) model, which is available in Temblor, today’s M=5.6 earthquake should not be considered surprising. This model uses global strain rates and seismicity since 1977 to forecast what the likely earthquake magnitude is in your lifetime anywhere on earth. From the Temblor map below, one can see that around the location of today’s event, a M=6.75+ is likely. Therefore, while the moderate event today may not have caused damage or loss of life, this region of South America, like the rest of the continent is prone to experiencing large and damaging earthquakes.

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This Temblor map shows the Global Earthquake Activity Rate (GEAR) model for the area around today’s M=5.6 map. This model uses global strain rates and seismicity since 1977 to forecast the likely earthquake magnitude in your lifetime anywhere on earth. What this figure shows is that in the location of today’s earthquake, a M=6.75+ is likely. Therefore, today’s quake should not be considered surprising.

References
USGS
European Mediterranean Seismological Centre

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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