M 7.0 earthquake does extensive damage in Alaska by disturbing economic activities,damaging roads,uprooting trees and electricity poles,breaking gas supply ,creating cracks in walls in houses and other infrastructure disturbances.

USGS reports that this Magnitude  7.0 earthquake occured at a place about 13km North of Anchorage in the state of  Alaska of USA.It occured at 2018-11-30 17:29:28 (UTC) at 61.340°N 149.937°W at 40.9 km depth.

 

After the main shock of magnitude 7 ,many smaller temblors continued to hit  parts of Alaska on Saturday .The authorities in Alaska city of Anchorage has launched extensive  recovery efforts.At many places power supply is disrupted. The electricity supply companies in Anchorage  are making all efforts to restore power to their consumers.

Bill Walker, the Governor of Alaska said that repair of roads damaged due to earthquake will take many weeks.

Fortunately,no deaths has been reported in this earthquake.However, the  Anchorage area witnessed sever  damage from this quake. Infrastructure like roads ,buildings,power lines etc are extensively damaged.At many places power supply is disrupted.

Gas companies are employing additional manpower to check leakage and restore supply in localities where gas connections are disrupted.

The President of USA,Donald Trump,has issued an emergency declaration for Alaska.

Earthquake in Alaska is common

Earthquake in Alaska is common as it witnesses  an earthquake about every 12 minutes on an average.However,most of these quakes are very small and insignificant.

Second largest recorded earthquake in the world However,Anchorage has witnessed the biggest ever earthquake of magnitude 9.2  on 28th March in 1964 in USA. This biggest ever earthquake caused 129 deaths and extensive damage and economic loss.The easternmost megathrust earthquake was the March 28, 1964 M9.2 Prince William Sound earthquake, currently the second largest recorded earthquake in the world. The event had a rupture length of roughly 700 km extending from Prince William Sound in the northeast to the southern end of Kodiak Island in the southwest. Extensive damage was recorded in Kenai, Moose Pass, and Kodiak but significant shaking was felt over a large region of Alaska, parts of western Yukon Territory, and British Columbia, Canada. Property damage was the largest in Anchorage, as a result of both the main shock shaking and the ensuing landslides. This megathrust earthquake also triggered a devastating tsunami that caused damage along the Gulf of Alaska, the West Coast of the United States, and in Hawaii. [caption id=attachment_3696 align=aligncenter width=803] Map showing pattern of earthquake waves of M 7.0 13km N of Anchorage Alaska,USA[/caption]

The U.S. Geological Survey  has cancelled the Tsunami warning issued earlier.It has said that no destructive tsunami has been recorded and no tsunami danger exists for the U.S. west coast, British Columbia and Alaska.

said that aftershocks are expected to continue for some time but projected there is a low probability, about 4 percent, of another earthquake equal or greater than magnitude 7.0. There federal agency said there is a 27 percent change of a magnitude 6.0 or greater.

Alaska witnessed a magnitude 7.9 earthquake last year southeast of Kodiak Island.

Seismotectonics of Alaska

The Aleutian arc extends approximately 3,000 km from the Gulf of Alaska in the east to the Kamchatka Peninsula in the west. It marks the region where the Pacific plate subducts into the mantle beneath the North America plate. This subduction is responsible for the generation of the Aleutian Islands and the deep offshore Aleutian Trench. Curvature of the arc [caption id=attachment_3697 align=alignnone width=815] The Aleutian arc extends approximately 3,000 km from the Gulf of Alaska in the east to the Kamchatka Peninsula in the west.[/caption] The curvature of the arc results in a westward transition of relative plate motion from trench-normal (i.e., compressional) in the east to trench-parallel (i.e., translational) in the west, accompanied by westward variations in seismic activity, volcanism, and overriding plate composition. The Aleutian arc is generally divided into three regions: the western, central, and eastern Aleutians. The Pacific plate is moving northwest Relative to a fixed North America plate, the Pacific plate is moving northwest at a rate that increases from roughly 60 mm/yr at the arcs eastern edge to 76 mm/yr near its western terminus. The eastern Aleutian arc extends from the Alaskan Peninsula in the east to the Fox Islands in the west. Motion along this section of the arc is characterized by arc-perpendicular convergence and Pacific plate subduction beneath thick continental lithosphere. This region exhibits intense volcanic activity and has a history of megathrust earthquakes.

Tectonic Summary

The November 30, 2018, Mw 7.0 earthquake near Anchorage, Alaska, occurred as the result of normal faulting at a depth of about 40 km. Focal mechanism solutions for the event indicate slip occurred on a moderately dipping fault striking north-south (dipping either to the east at about 30 degrees, or the west at about 60 degrees). At the location of this earthquake, the Pacific plate is moving towards the northwest with respect to the North America plate at about 57 mm/yr, subducting beneath Alaska at the Alaska-Aleutians Trench, approximately 150 km south-southeast of this event. The location and mechanism of this earthquake indicate rupture occurred on an intraslab fault within the subducting Pacific slab, rather than on the shallower thrust-faulting interface between these two plates. Earthquakes are common in this region. Over the past century, 14 other M 6+ earthquakes have occurred within 150 km of the November 30, 2018 event. Two of these – a M 6.6 earthquake in July 1983 and a M 6.4 event in September 1983 – were at a similarly shallow depth and caused damage in the region of Valdez. The M 9.2 great Alaska earthquake of March 1964, was an interface thrust faulting earthquake that ruptured over several hundred kilometers between Anchorage and the Alaska-Aleutians trench, and to the southwest.   ..... .... Login with Google and support us
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