From Yellowstone to Hawaii to the Gulf of Mexico, the Earth has been shaking and trembling in ways that have some people wondering what’s going on, and others warning that something bigger – much bigger is on the horizon.
Los Angeles Times The conversation about what’s happening only intensified on Tuesday after residents of Southern California were jolted awake with a 4.5 earthquake at 4:49 am. The epicenter was near San Gorgonio Pass about 85 mile east of downtown Los Angeles, but it was felt from San Diego to Santa Clarita. Here’s more from the Los Angeles Times: Tuesday’s earthquake occurred along a section of the San Andreas fault zone known for having smaller earthquakes as well as larger ones, said Caltech seismologist Egill Hauksson. It’s known as the “San Gorgonio knot,” named because there are so many small faults that intersect there as the San Andreas fault bends from a northwest-southeast direction to an east-west orientation.
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Wikimedia Commons On other parts of the San Andreas fault, where the geometry is simple and the fault is smooth, smaller earthquakes are much less likely to happen, because once a temblor begins, it can more easily grow into a larger earthquake. “Historically, this area around Mt. San Gorgonio is the only part of southern San Andreas fault that produces smaller quakes,” said the Southern California Seismic Network report, which was co-written by Hauksson. Since 1932, there have been 46 earthquakes of magnitude 4 or greater within six miles of Tuesday’s earthquake. Hauksson called today’s quake just a minor adjustement in build-up of strain in the tectonic plates that meet alont the San Sandreas fault.
Flickr More from the LA Times: Every 100 years, the Pacific plate moves about 16 feet northwest relative to the North American plate. That accumulating strain must be released, eventually, by large earthquakes. A U.S. Geological Survey scenario of a hypothetical magnitude 7.8 earthquake envisions the rupturing of the San Andreas fault between the Salton Sea and Lake Hughes near the Grapevine section of Interstate 5.
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Wikimedia Commons Such a quake could cause a death toll of 1,800; sever pipelines, power lines, roads, railways and aqueducts that cross the San Andreas fault, such as along the Cajon Pass (Interstate 15), the San Gorgonio Pass (Interstate 10) and along Highway 14; and cause strong shaking in downtown L.A. for 55 seconds — nearly eight times longer than what was felt in the 1994 Northridge earthquake. Let’s hope that scenario doesn’t play out any time soon!
