Cal Tech is monitoring this earthquake swarm closely because of its proximity to other faults, notably the Imperial and San Andreas, although there is no indication that this swarm won’t subside like the many swarms that have occurred in this area.
An earthquake swarm began the morning of August 10, 2020 PDT under the Southern part of the Salton Sea along the Brawley Fault Zone, a fault that connects the San Andreas Fault to the Imperial Fault, The swarm started at 8:09 a.m. PDT August 9. The largest, at 8:56 a.m. PDT, was a magnitude 4.6. Over 90 earthquakes have occurred so far, ranging from 1.3 to 4.0. Where’s Dwayne Johnson when you need him?
Dr. Jen Andrews, staff seismologist at Cal Tech Seismological Laboratory was able to verify that the quakes are not related to any magmatic movement or geothermal plant activity, but appear to be related to the Elmore Ranch and Brawley fault zone faults. Fault depths are within expected range for these fault zones, ranging from 1.2 to 17.9 kilometers depth.
There were 3 previous swarms along the zone in 2001, 2009 and 2016, north of the present swarm.
However the U.S.G.S. (United States Geological Survey) is currently running scenarios including data from this swarm, to see if the swarm could be impacting seismic stress – relieving or increasing it – in the area. The situation, although not a cause for alarm, is significant enough to merit ongoing monitoring and study by Cal Tech and the U.S.G.S.
Seismically Active Area
The Brawley Fault last ruptured October 15, 1979 as part of the 6.4 magnitude Imperial Valley earthquake. During that quake, 13 kilometers (8 miles) of the Brawley fault ruptured, along with 30 kilometers of the Imperial Fault and one kilometer of the Rico fault.
The Elmore Ranch fault last ruptured on November 23, 1987 in the 6.2 magnitude Elmore Ranch earthquake. The next day the nearby Superstition Hills fault ruptured in a 6.6 magnitude quake.
Concerns of Volcanic Activity
There was some theorizing that these quakes could be related to magmatic activity, but according to the source at Cal Tech, that is not the case. There is always concern about quakes in the southern end of the Salton Sea because of the presence of potential volcanic activity. The earth’s crust has fractured into multiple plates which move around, carrying continents and oceans, powered by upwelling magma from deep within the earth.
The San Andreas Fault, which runs along the eastern edge of the Salton Sea, is the boundary between two gigantic plates, the Pacific and the North American. At this part of the boundary, the plates are pulling apart, creating the Salton Trough, or rift valley, in which lies the Salton Sea. The trough is so deep that the surface of the Salton Sea is 224 feet BELOW sea level. The continental crust below the sea and the rest of the rift valley is so thinned by this spreading that magma has been able to reach the surface as recently as 1800 years ago, forming the Obsidian Buttes at the southern end of the Salton Sea. The area is on the U.S.G.S. Earthquake Monitoring list because of the potential for future eruptions.
Mud Volcanoes
The proximity of magma to the surface in this area has enabled the operation of geothermal energy plants on the eastern shore of the Sea. The magma also has produced a fascinating field of bubbling mud geysers at the southeastern end of the Salton Sea. Water steam-heated up to 700° F. by magma carries sediment and minerals to the surface, creating mini-mud volcanoes or bubbling pools of mud.
Further Reading
- https://www.usgs.gov/volcanoes/salton-buttes/
- https://scedc.caltech.edu/significant/imperial1979.html
- https://earthobservatory.nasa.gov/images/81711/salton-trough
- https://scedc.caltech.edu/significant/elmoreranch1987.html
- https://scedc.caltech.edu/significant/brawley.html
- https://earthobservatory.nasa.gov/images/81711/salton-trough
- https://volcano.si.edu/volcano.cfm?vn=323200
- https://en.wikipedia.org/wiki/Salton_Sea
- https://en.wikipedia.org/wiki/Salton_Trough
- https://www.desertsun.com/story/tech/science/energy/2017/08/16/warren-buffetts-berkshire-hathaway-nixes-salton-sea-geothermal-plant/570131001/
- https://en.wikipedia.org/wiki/Tectonics
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