Saturday, 3 August 2013

Magnitude 4.5 Earthquake off the coast of northern California.

A Magnitude 4.5 Earthquake at a depth of 19.3 km occurred roughly 20 km off the coast of Eureka in north California at 7.25 pm local time on Friday 2 August 2013 (2.25 am on Saturday 3 August, GMT), according to the United States Geological Survey. This is a moderately large quake, but unlikely to cause any problems this deep and this far offshore, though it was felt throughout the Eureka area.

The approximate location of the 2 August 2013 Eureka Earthquake. Google Maps.

California is extremely prone to Earthquakes due to the presence of the San Andreas Fault, a tectonic plate margin that effectively bisects the state. The west of California, including Santa Barbara and Los Angeles, is located on the Pacific Plate, and is moving to the northwest. The east of California, including Fresno and Bakersfield is on the North American Plate, and is moving to the southeast. The plates do not move smoothly past one-another, but constantly stick together then break apart as the pressure builds up. This has led to a network of smaller faults that criss-cross the state, so that Earthquakes can effectively occur anywhere.

Witness accounts of Earthquakes can help geologists to understand these events and the underlying structures that cause them. If you felt this quake (or if you were in the area but did not, which is also useful information) then you can report it to the United States Geological Survey here.



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1 comment:

  1. I was at home in Eureka, California reading when the 8/2/13 incident occurred at approximately 7:25. At first I thought that it was an explosion in that a sound similar to such preceded the event. That was followed by a distant rumble that became louder as it approached, then the shake. I have lived in California all of my life and thought that the
    magnitude might be greater. As it was daylight, I exited the house to question others who were standing on the street. One person shouted to another, "Did you feel that?" A gardener two houses away using a leaf blower felt nothing as the equipment vibrated.
    It is interesting to note that this is the second time that I have experienced the sound of
    an explosion before a quake. Also, the rumbling
    sound became more distinct as it traveled toward
    me.

    ReplyDelete