Large earthquake strikes offshore of El Salvador

Large earthquake strikes offshore of El Salvador

Magnitude 7.2, offshore south of San Miguel, El Salvador

A large subduction earthquake struck about 100 kilometres off the coast of El Salvador at 03:51 UTC, causing damage in many several communities near to the Pacific coast. Reports indicate minor damage in San Miguel, including a major hospital and some walls with heights in excess of 4 metres.

The earthquake was caused by the subduction of the Cocos Plate below the Caribbean Plate. Earthquakes occur commonly along this convergent plate boundary, including the April Mw 6.6 quake in Nicaragua, and the March Mw 6.1 quake. Quakes are rarely deadly, and the last magnitude 7.0+ quake in this region was the magnitude 7.6 quake in Costa Rica in 2012.

Nicaragua's seismic institute INETER has recorded nine aftershocks to the earthquake over Ml 3.0, the largest a magnitude 4.6 at 13:27 UTC. This is about 1.5 magnitude levels below the expected magnitude for the largest aftershock, according to the Gutenberg-Richter Law. There also appear to have been a relatively low number of aftershocks over Ml 3.0; for example, the Van Earthquake of October 2011 had 34 aftershocks over magnitude 4.0 in the first ten hours of its aftershock sequence, which is about 11 times as many as this quake has had in the same time period.

List of Aftershocks (INETER)

Ml 4.0 - 04:01 UTC

Ml 3.8 - 04:06 UTC

Ml 3.6 - 04:47 UTC

Ml 3.4 - 04:49 UTC

Ml 3.6 - 05:04 UTC

Ml 4.2 - 06:09 UTC

Ml 3.7 - 06:11 UTC

Ml 3.1 - 07:18 UTC

Ml 4.6 - 13:27 UTC

This article was written on the 14th October 2014 by J H Gurney.