Tuesday 18 March 2014

Los Angeles shaken by Magnitude 4.4 Earthquake.

The United States Geological Survey recorded a Magnitude 4.4 Earthquake at a depth of 9.9 km, roughly 9 km to the northwest of Westwood, at about 6.25 am local time (about 1.25 pm GMT) on Monday 17 March 2014. There are no reports of any damage or casualties associated with this quake, though it was felt across much of southern California.

The 17 March 2014 Los Angeles Earthquake caused minor disruption, but no serious damage. Getty Images.

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.

The approximate location of the 17 March 2013 Los Angeles Earthquake. Google Maps.

Typically the Los Angeles Basin would be expected to suffer a quake in excess of Magnitude 4.0 roughly once per year, but this is the first such event since the Magnitude 5.5 Chino Hills Earthquake of July 2008. This has led to some concern in the area, as an absence of seismic activity near an active fault can indicate a build up of stress leading to an exceptionally large quake. The 17 March 2014 event will go some way to assuaging these fears, although there is some concern that it may preclude a larger event.

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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