A new paper released by the US Geological Survey states that the chance California will suffer an earthquake with a magnitude bigger than 8.0 on the Richter scale has gone up to 7%, up from the previous estimate of 4,7%.
The risk of lower magnitude, but still serious earthquakes, is even higher, especially in the San Francisco Bay Area. The study itself, named the “Third Uniform California Earthquake Rupture Forecast” bases its estimates on a time span ranging to 2044.
“The new likelihoods are due to the inclusion of possible multi-fault ruptures, where earthquakes are no longer confined to separate, individual faults, but can occasionally rupture multiple faults simultaneously” explained lead study author Ned Field, a research at the USGS.
The paper also calculates the chance earthquakes will happen alongside individual fault lines that run through the state. The biggest possibility of an earthquake with a magnitude of at least 6.7 is around Hayward Fault line, near the Santa Clara county city of Milpitas, with 22.3% chance of serious seismic activity over the next thirty years.
However, the frequency of earthquakes happening near the 6.7 mark has decreased from almost one every 5 years to one every 6.3 years. California is such a high seismic activity-risk zone because of the complex and intertwined system of fault lines it has.
An earthquake of magnitude 8.0 or more would be only the second to hit the lower 48 US states in the history of recorded seismic activity, and the first since the formation of the United States as a nation.
The only previous one was the Cascadia Subduction Zone earthquake, which hit a 600 mile wide region pertaining today to the states of California, Washington and Oregon with a magnitude of 9.0 in January 1700. It was so intense that records of it suggest it also created damage on the shores of Japan.
Besides that, the largest earthquake in California was the Fort Tejon 1857 earthquake, with a magnitude of 7.9. However, earthquakes don’t necessarily need to match its intensity to cause widespread disaster.
The 6.7 magnitude Northridge earthquake in 1994 managed to destroy an Interstate 5 connector and caused over $15 billion in damage. The consequences of a large earthquake range from the destruction of houses and loss human lives to irreparable damage to irrigation systems, transport networks and disruption of communications infrastructure.
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