Recent earthquakes in anchorage alaska9/13/2023 Aftershocks were expected to continue for around 300 days after the mainshock. Two more aftershocks hit on February 6, the first with a magnitude of 4.1, and the second coming 23 minutes later with a magnitude of 3.7. By December 3, 170 aftershocks with a magnitude over 3.0 had been noted. Over 80 aftershocks of various magnitudes were recorded throughout the day, with at least three having magnitudes greater than 5.0. Map of 2018 Anchorage earthquake and aftershocks. Aftershocks Magnitude of 2018 Anchorage earthquake and aftershocks. This faulting in the Pacific Plate is caused by downward bending while the plate is being forced under Alaska. This is a different mechanism than megathrust faults in the region, which do occur on the plate boundary itself. This implies that the earthquake was an intraslab earthquake within that plate, rather than at the plate boundary between the Pacific and North American Plates beneath the Anchorage area. The depth and mechanism are consistent with faulting within the down-going Pacific Plate. A fault dipping at 29° towards the east gives the best match to the observed seismic waveforms. The focal mechanism shows that the earthquake was a result of normal faulting. The earthquake had a magnitude of 7.1 on the moment magnitude scale using a centroid moment tensor inversion of the W-phase. This earthquake is more similar to the 2001 Nisqually earthquake located near Tacoma, Washington, than to the 1964 megathrust earthquake. Though earthquakes are common in Alaska, they often occur out at sea. The 1964 earthquake, with a magnitude of 9.2, was the largest earthquake in American history and the second largest to ever be recorded anywhere in the world. The region has experienced severe earthquakes in the past, including several megathrust earthquakes. Near Anchorage, the plates are converging at a rate of 57 mm per year. Southern Alaska lies at the eastern end of the Aleutian Trench, where the Pacific Plate is subducting beneath the North American Plate. The National Tsunami Warning Center-itself located inside the quake zone, in Palmer, Alaska, 42 miles (68 km) northeast of Anchorage-issued tsunami warnings for nearby coastal areas, including Cook Inlet and the Kenai Peninsula, but they were lifted shortly after. The earthquake could be felt as far away as Fairbanks. It was followed six minutes later by a magnitude 5.7 aftershock centered 2.5 miles (4.0 km) north-northwest of the municipality. The earthquake's epicenter was near Point Mackenzie, about 10 miles (16 km) north of Anchorage, and occurred at a depth of 29 miles (47 km). AKST (17:29 UTC), a magnitude 7.1 earthquake hit Anchorage in South Central Alaska.
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