LA's Fault System Actually In Quiet Period
The "urban fault network" under the Los Angeles metropolitan area--which does not include the San Andreas fault--is actually in a period of relative quiet. Steve Mirsky reports.
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This is going to surprise anybody who’s ever been shaken awake by a quake in southern California. But geologists say that the Los Angeles basin is actually in a period of low seismic activity and has been for about the last thousand years. That’s according to research published in the September issue of the journal Geology. The seismic lull is marked by relatively smaller and fewer earthquakes. That’s compared with other periods with a lot of rumbling and crumbling. The period of big seismic activity in the LA basin that ended a thousand years ago lasted about four thousand years. Long-term data on seismic activity indicates that the calm period lasts about 1500 to 2000 years, which gives LA another 500 to 1000 years off.
Now, the researchers are specifically referring to what’s called the urban fault network, which is under the LA metropolitan area. It does not include the San Andreas fault, which can still throw the occasional big one around. About 10 major San Andreas biggies have happened during the current LA basin lull. Nevertheless, if the current lull ends in the next millennium, LA’s future could be very shaky.
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