From temblor: “M=6.3 earthquake in the Aegean Sea near the Greece-Turkey border causes injuries and damage”

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temblor

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Vatera, in southern Lesbos experienced strong shaking from today’s M=6.3 earthquake. Numerous reports of damage have come in from this tourist hotspot in the eastern Aegean Sea. (Photo from: villapouloudia.gr)

At 3:28 p.m. local time, a M=6.3 earthquake struck just south of the Greek Island of Lesbos (Lesvos), near the international border with Turkey. So far, there have been 33 aftershocks in close proximity to the mainshock, with the largest being a M=4.9. According to the USGS, severe shaking was felt close to the epicenter, and there are numerous reports of damage on Lesbos, a popular tourist hotspot (see video below). Based on the USGS PAGER system, fatalities are unlikely, while economic losses are estimated to be between $10-100 million.

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This Temblor map shows the location of today’s M=6.3 earthquake south of Greek island of Lesbos. The faults on Lesbos’ southern coastline have been added to this map as they are the closest mapped active faults to today’s epicenter. Having said that, today’s quake, which was extensional in nature, likely occurred on a different structure.

The Greek island of Lesbos, is home to approximately 87,000 people, making it the most populated in the Eastern Aegean. The tectonic activity in the area is associated with the broader evolution of the Aegean Sea. Along Lesbos’ southern coastline, and extending offshore are several active faults with components of both left-lateral strike-slip and extensional motion. The main faults, which have been added to the Temblor map above are the Polichnitos-Plomari and Aghios Isidoros-Cape Magiras faults. The Polichnitos-Plomari Fault is primarily extensional, though it also has a strike-slip component. Activity along it is related to theremal activity from the nearby Polichnitos geothermal field. The Aghios Isidoros-Cape Magiras Fault on the other hand is primarily extensional with a small amount of strike-slip motion. While these faults are close to the epicenter of today’s quake, based on the strike of the event, which was almost purely extensional it likely occurred on an additional, unmapped structure within the Aegean Sea.

Due to the quake’s moderate magnitude, and shallow (9 km) depth, shaking was widely felt across the region, including in Athens, the Turkish Cities of Izmir and Istanbul, and Sofia, the capital of Bulgaria. Based on the USGS Shakemap and felt reports from the European-Mediterranean Seismological Centre, over 50 million people were exposed to some degree of shaking. However, damage appears to be isolated to the island of Lesbos, where building facades have come down, and 10 people have been injured.

The video below shows damage sustained on Lesbos in today’s M=6.3 earthquake

In addition to the M=6.3 mainshock, and the 33 aftershocks in close proximity, there also may have been two remote, dynamically-triggered aftershocks, up to 75 km away. One of these, a M=3.3 10 minutes after the mainshock was less than 15 km from Izmir. While it is possible that these quakes are incorrectly located, it is possible that they are remote aftershocks.

Based on the Global Earthquake Activity Rate (GEAR) model, which is available in Temblor, today’s M=6.3 earthquake should not be considered surprising. This model, which uses global strain rates and seismicity since 1977 forecasts what the likely earthquake magnitude is in your lifetime anywhere on earth. From the Temblor map below, one can see that in the location of today’s quake, a M=6.5+ is possible. Therefore, while this earthquake was damaging and caused injuries, a larger quake in the region could happen, resulting in more extreme damage.

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This Temblor map shows the Global Earthquake Activity Rate (GEAR) model for much of the area around the Aegean Sea. From this map, one can see that in the area around today’s M=6.3 earthquake, a M=6.5+ quake is possible. This map also shows a possible remote aftershock and the cities of Athens, Izmir, Istanbul, and Sofia, where shaking from today’s quake was felt.

References
European-Mediterranean Seismological Centre (EMSC)
Chatzipetros, A., Kiratzi, A., Sboras, S., Zouros, N., Pavlides, S., Active Faulting in the nore-eastern Aegean Sea Islands, Tectonophysics 597-598 (2013) 106-122
USGS

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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.

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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.

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