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Salton Trough and Earthquake Risk


Last updated 10/12/2016 at 10:25am

Following the discovery of a new fault under the Salton Sea by a team of seismologists, questions have been raised in the press as to whether the new information raises the risk of larger quakes. According to the teams provisional, and somewhat speculative data, the fault is believed to be many thousands of years old, and lies roughly parallel to, and is only kilometers from, the famous San Andreas fault.

As part of a National Science Foundation-funded project to get seismic images of the Salton Sea, the team stumbled upon the fault. Rather than focusing on the salt layers piled up in the sea’s belly, the team’s seismic imagers detected deformation and asymmetry in the sediment beneath the surface—evidence of a fault. “We were expecting to see some little faults within the profile, but not something like this,” says Valerie Sahakian, lead author of the study and a seismologist at USGS’ Earthquake Science Center. “Because it runs so close to the San Andreas, they could interact, but we don’t know how.”

Despite growing alarm about what the Salton Trough fault means for the San Andreas’, finding a new fault nearby doesn’t increase earthquake risk.

It’s impossible to know if the Salton Trough fault is taking the San Andrea’s share of the strain. Seismologists still aren’t clear on how the Salton Trough fault fits into its neighboring fault system. The ends of the San Andreas and Imperial faults fall a little to the side of each other, scientists expected to find small faults running perpendicular to the San Andreas, not parallel. “When you get to an offset, the relative motion of plates has to be accounted in another complicated way, with lots of interactions with little faults,” says Richard Allen, director of the seismological lab at Berkeley. “The discovery of this new fault forces the scientific community to probe what we do and don’t understand understand about the accommodation of strain between San Andreas and Imperial fault.”

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