So, if you’re on top of where the epicenter is in California, you are zero kilometers away from where the earthquake is shaking. This earthquake occurred at a depth of about 32 kilometers, which is a good deal down in the earth, meaning that even if you were standing directly on top of where the earthquake was happening, you’re still 30 kilometers away from it.Ĭontrast that with something like Southern California where you can have very significant human impacts from significantly smaller events, because those faults rupture the surface. So it’s fairly sparsely populated.īut maybe more importantly is the depth of the earthquake, how deep it is in the earth. The nearby towns that received heavy shaking in places like Perryville only have 100 or so people living in them. First, the Aleutians are very sparsely populated. Stephen Holtkamp: There are a couple of factors here. The following transcript was lightly edited for clarity. Holtkamp told Alaska Public Media’s Casey Grove that it caused little apparent damage because of it remoteness and depth. Seismologist Stephen Holtkamp with the Alaska Earthquake Center is one of the researchers studying Wednesday night’s quake. Still, it was the largest earthquake in the United States in 50 years, a classic Alaska subduction zone earthquake, where the tectonic plate beneath the Pacific Ocean is subducting - sliding under - the North American plate upon which Alaska sits. RELATED: Major quake hits off the coast of Alaska, triggers tsunami warnings The magnitude 8.2 earthquake that struck off Alaska’s southwest coast Wednesday night gave nearby residents a good shake and triggered tsunami warnings, but there were no large waves or any immediate reports of major damage or injuries. Photographs of the aftermath of the NovemM7.Screenshot from Alaska Earthquake Center map.US Geological Survey: Earthquake preparedness information.UAF Geophysical Institute: General earthquake information.Three seismometers are located within the park, and other efforts to install portable seismometers or instruments regarding the movement or nature of the earth’s crust are ongoing.įor additional information on seismology of the Denali or Alaska, visit: The park supports active research on seismic activity, and collaborates with the Alaska Earthquake Information Center (AEIC) and other groups to better monitor and understand the seismic activity in and near the park. Although the park area only suffered spilled shelf items and a few road sags, at other locations about 166 km (100 miles) east of the park, roads were fractured, several homes were jostled off their foundations, and the Trans-Alaska oil pipeline lost some of its support members. The epicenters (point on the earth surface where the quakes originate) of each of these large earthquakes was about 50 km (30 miles) east of the park, on the Denali fault. The M7.9 was the largest earthquake to occur in the interior of the state in recorded history. On October 23, and November 3, 2002, the park and most of central and southern Alaska experienced a foreshock of M6.3, and a mainshock of M7.9. Historically, seismic events have not been known to damage man-made structures within the park. In November and early December of the year 2000, two earthquakes occurred on the north boundary of the park at M5.7 and M5.0, which shook local residences, and was felt as far away as Fairbanks. On May 21, 1991, a M6.1 earthquake occurred at a depth of 112 km right under Denali, and was noticed by climbing teams on the mountain who reported numerous massive snow and ice avalanches. Larger magnitude events (>M4.5) are not common in the park, but records show that a few have occurred. Generally, the highest magnitude events that occur in the park in any given year are in the neighborhood of the mid to high M4’s, and again, are often right under Denali or near the Kantishna Hills on the Northwest side of the park. Numerous faults, including the Denali fault (a major fault system), demonstrate a long history of active plate tectonics and associated earthquake activity. This seismic activity at the root of Denali suggests that uplift of the mountain continues to this day. A large share of earthquake activity is right under Denali, frequently, at very deep locations (90 – 125 km/54-75 miles deep), providing few people the opportunity to experience them. But these events are not usually felt by anyone because of the low magnitudes. Most of these earthquakes (about 70%), average between M1.5 and M2.5, and often occur near the surface (0-15 km/0-9 miles deep) at locations all over the Park. It is estimated that there are some 600 seismic events per year within the park boundaries at magnitude 1 (M1) or greater. Because of active plate tectonics, earthquakes are frequent in the Denali area.
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