Scientists from the Massachusetts Institute of Technology, the University of California at Riverside and the US Geological Survey have conducted a new study, which found that faults in the state of California pose a much more serious threat of destruction than previously thought.
Experts studied earthquakes that hit the Californian cities of Napa and San Francisco in 2014. The element had a magnitude of 6 and occurred on August 24th. At the same time, first an earthquake followed in the city of Napa, and after the aftershocks subsided, the blow fell on San Francisco. Then a seismic event led to the destruction of buildings and infrastructure.
A team of scientists led by Michael Floyd, using satellite data and GPS measurements, established that the earthquakes first occurred due to stress in the Napa Valley fault. Many aftershocks followed, and after a short lull the blow fell on San Francisco.
Previously, it was believed that earthquakes are the result of the release of energy, which is accumulated as a result of surface movement along faults, after which this stress allegedly decreases. However, the results of the study showed that this is not entirely true. Floyd and his colleagues found that surface movement in the fault region leads to earthquakes, with the result that the stress on one geological fault decreases, but at the same time increases in the region of nearby faults. At the same time, in other places the surface can also begin to move. As a result, aftershocks after the main tremor can continue even for a month, and even provoke new powerful tremors, as happened in San Francisco on August 24.
As the researchers note, such events are caused by different soil structures in different parts of the state. It is worth noting that the new study fully supports the theory that one large earthquake in California could trigger a series of catastrophes on the domino principle. Then the study was carried out by experts from Mexico, the University of California at Davis and the US Geological Survey. At the same time, the new feature of the faults poses an even greater threat than geologists previously thought.
The research results are published in Geophysical Research Letters.