Sunday, July 1, 2012

Strong Quake Swarm SSW of Cerro Prieto, Mexico

A minor swarm of earthquakes hit several miles SSW of Cerro Prieto in Mexico, near the US border (and my hometown of San Diego County). The largest quake was measured at 4.7 by USGS, however there were two subsequent tremblors of 4.6, and 4.1, as well as many magnitude 3 and under. This occurred along the same fault line that eventually transforms into the San Andreas fault, and begins between mainland Mexico, and Baja California, Mexico.

No damage has been reported so far.

The epicenters of the quakes are several miles south of the epicenter of the last large quake in the region, (a 7.4 magnitude quake in 2010 that was dubbed "The Easter Quake). I was present very near the epicenter and experienced this firsthand. The current quake swarm is likely a result of this quake, as the region has experienced many minor to somewhat large tremors since the Easter Quake. This is most likely due to crustal adjustments, and settling, and not a precursor toward volcanic eruption. However just NW of the epicenter lies a more than 10,000 year old small volcano cone name Cerro Prieto. Just NNW of that cone, lies the Salton Sea, another volcanic center which has also experienced Holocene eruptions, and is, as well as Cerro Prieto, an actively producing geothermal field.

The GVP describes local Cucapas Indian legends of a monster rising from the earth and emitting "Fire tongues", which has been interpreted to mean a description of the growing volcano in its infancy. While neither Cerro Prieto nor the Salton Sea has seen any volcanic activity during recent historical times, it is an area that will likely have an eruption in the earth's future. Current displays of volcanic activity can be found at the Salton Sea by way of fumeroles, and mud volcanoes, as well as the geothermal power plants in the area. In the Cerro Prieto region, geothermal plants dot the area, and during some quakes, it has been reported that spouts of sulfuric smelling water, red in color, emanate from the landscape like geysers, however only briefly.

During the 7.4 magnitude quake, the area was lightly reported to have had increased surface activity from geothermal forces.

The activity in the area is caused by light crustal spreading, and impaction northward. As the plate grind North, they also spread slightly at the Pacific/North American Plate boundary, near San Diego, CA, pulling Baja California away from mainland Mexico, yet upwards toward the mainland USA.

The current quakes are not volcanic in nature, however the area will someday experience eruptive activity. In the near future however, this is not likely to happen.

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