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Alaska EarthQuake Measures 7.1 Magnitude, Leaves Less Impact

Sparingly populated Alaska region was hit by 7.1 magnitude earthquake at 1:30 AM with its epicentre located 85-KM from Anchor Point in Kenai peninsula, said US Geological Survey (USGS) but no damages have been reported so far. Otherwise, the epicentre is the same place where the world’s second largest global earthquake was ever recorded, the M 9.3 Great Alaska earthquake of March 27, 1964.

Though seismologist Michael West said it was one of the strongest earthquakes in decades, Alaska experienced 7.9 earthquake last year in Aleutian Islands. With aftershocks still going on in the range of 2.5 to 4 magnitude in the vicinity, Anchorage residents and Valdez police departments said they hadn’t received any reports of injuries.

Kenai battalion chief Tony Prior said, "No injuries. Thank God,” he said. “The second one was a major explosion. We’re fortunate that no one was hurt.” Nearly 30 homes were evacuated and put up in a shelter run by the Kenai National Guard Armory.

"It started out as a shaking and it seemed very much like a normal earthquake. But then it started to feel like a normal swaying, like a very smooth side—to—side swaying,” said Nusunginya, director of audience at the Peninsula Clarion newspaper told media.
There was considerable confusion about the magnitude as USGS first reported it as 7.1M and later scaled it down to 6.8M but soon reverted it to 7.1M. Soon 4.7M aftershock hit the region while the aftershocks are in the range of 2M now.

The impact was seen in power outages from the Matanuska Electric Association and Chugach Electric in the Anchorage area with about 4,800 customers complaining that there was no power.

2016-01-24 10:30:30 (UTC)
2016-01-24 16:00:30 (IST)

Nearby Cities
83km (52mi) E of Old Iliamna, Alaska
261km (162mi) SW of Anchorage, Alaska
295km (183mi) SW of Knik-Fairview, Alaska
648km (403mi) SSW of College, Alaska
1024km (636mi) W of Whitehorse, Canada

Tectonic View

The earthquake southwest of Anchorage, Alaska, occurred as the result of strike-slip faulting at intermediate depths, within the subducted lithosphere of the Pacific plate, said USGS. In the region of the earthquake, the Pacific plate moves northwestward with respect to North America at a rate of 60 mm/yr, and begins its decent into the mantle at the Alaska-Aleutian Trench almost 400 km to the southeast of this earthquake.

Earthquakes like this event, with focal depths between 70 and 300 km, are commonly termed "intermediate-depth" earthquakes. Intermediate-depth earthquakes represent deformation within subducted slabs rather than at the shallow plate interfaces between subducting and overriding tectonic plates. They typically cause less damage on the ground surface above their foci than is the case with similar magnitude shallow-focus earthquakes, but large intermediate-depth earthquakes may be felt at great distance from their epicenters. Earthquakes have been reliably located to depths of about 220 km in this region.

Southern Alaska frequently experiences earthquake activity in relation to the Pacific:North America subduction zone plate boundary. The shallow interface between these plates to the southeast of the January 24, 2016 earthquake was the location of the second largest global earthquake ever recorded, the M 9.3 Great Alaska earthquake of March 27, 1964.

Also 17 earthquakes of M 6 or larger have occurred within 250 km of the January 24, 2016 earthquake, the largest being an M 7.0 aftershock of the Great Alaska earthquake in July 1965. The previous largest intermediate depth earthquake in the region was a M 6.8 event in July 2001, 120 km to the southwest of the epicentre.

[tags, alaska earthquake, magnitude, confusion, usgs, impact, power outage, injuries, no deaths, no injuries, evacuation, anchorage ]

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