One of the interesting features of this earthquake is that it did NOT generate a large tsunami.
This research helps with assessing hazard and risk. How does this research help with assessing tsunami hazard risk? So, it helps to have a larger motion to measure when the noise level is high. That means it is hard to measure the acoustic range as precisely as we can measure the GPS part. The GNSS-acoustic position measurements of the seafloor's motion are quite noisy because the speed of sound through the water is very sensitive to ocean temperature and varies a lot with time. That means a large signal for us to measure, which is always helpful. Large earthquakes are important to study because they produce the largest motions and cause the largest changes in stress within the Earth. The most important thing we learned is that the total movement at the GPS-acoustic site offshore was much larger than had been predicted by earlier models for the earthquake. Why is studying the Chignik, Alaska, earthquake important to earthquake research? This technique is called GPS-acoustic positioning, and by repeating the survey measurements before and after the earthquake, we can measure how much the seafloor moved, and use that to better determine how the fault moved. Radio signals from the GPS satellites will not travel through water, so to get any data we must combine the GPS positioning of a floating platform with acoustic, or sound wave, positioning of the same platform relative to an array of transponders, which pick up and emit signals on the seafloor. On land, we can set up Global Positioning Systems or Global Navigation Satellite Systems-GPS and GNSS, respectively-instruments and record the positions of the plates fairly easily, but the part of the fault that slipped in the earthquake is located pretty far away from land. The biggest challenge is that the fault comes to the surface on the ocean bottom far offshore, and there are kilometers of water in the way! We need to measure how the Earth was permanently moved by the earthquake, and we really need measurements that are made right above the part of the fault that slipped. What are the challenges with studying the Alaska-Aleutian fault? This research appeared recently in the journal Science Advances. Freymueller is an internationally recognized expert in geodesy, or the study of Earth's size and shape, and serves as MSU's Endowed Chair for Geology of the Solid Earth. One in October had a magnitude of 7.4, while another quake in July 2020 measured 7.6.Jeffrey Freymueller, a professor in the College of Natural Science at Michigan State University, is researching this earthquake to learn more about exactly where that slip occurred (and how much) to better understand how faults work and to help evaluate the risk of future earthquakes and tsunamis. The 1964 quake claimed the lives of more than 250 people, destroying Anchorage and unleashing a tsunami that wreaked havoc across the Gulf of Alaska.Īlaska was struck by two weaker earthquakes last year. An earthquake in Anchorage in 2018 caused significant damage Image: Reuters/N. The US state is part of the seismically active Pacific Ring of Fire where earthquakes are very common. Has Alaska been hit by earthquakes before?Īlaska was was hit by a 9.2-magnitude earthquake in March 1964, the strongest ever recorded in North America. When plates snap back into position, the energy from this movement can cause huge waves to form. Japanese public broadcaster NHK reported that there is no risk of tsunami damaging Japan's coast after it said there might be small changes to tide levels.Įarthquakes are the result of sudden movement along faults within the Earth caused by the release of built-up pressure at plate boundaries. Officials at the Pacific Tsunami Warning Center scrapped the alerts when it emerged that the threat was not as great as first feared. In Seward on the Kenai Peninsula, south of Anchorage, sirens blared as residents were ordered to move to higher ground. In Alaska, there were no immediate reports of injuries or damage. Several coastal communities had been evacuated as a precaution. But authorities later canceled those warnings. Tsunami warnings were issued for Alaska, Hawaii, and the Pacific territories of Guam and the Northern Mariana Islands. Image: Deutsche Welle (DW) Why were the tsunami warnings canceled? The earthquake hit 56 miles (91 kilometers) southeast of the town of Perryville, some 500 miles from Anchorage, Alaska's biggest city. It measured the quake as having a depth of 35 kilometers (21.7 miles). The US Geological Survey (USGS) had initially reported that the magnitude was 7.2. US authorities lifted a string of tsnuami warnings after an earthquake of magnitude 8.2 struck the Alaska Peninsula on Thursday.
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