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Know the West

Is the San Andreas slipping?


Fill the water jugs and put the wrench back near the gas valve, Southern Californians, the Big One’s about to blow! Or not. You never can tell with these things. But geologists are watching closely a “swarm” of recent earthquakes on the Southern San Andreas Fault, the largest of which logged in at 4.8 on the moment magnitude scale at five minutes till 5 this morning.

“Science Dude” Gary Robbins of the Orange County Register reports that the many little quakes that slipped over the weekend had already prompted the Scripps Institution of Oceanography to issue what he calls a “highly unusual news advisory” about the minor temblors. “While earthquake swarm events are not precursors or indicators of a larger earthquake event,” it said, “they are jolting reminders that Southern California will experience the Big One soon.”

The science jury is still hung over whether many smaller quakes precede – or even provoke – a large one, and as Robbins reports, geologist Susan Hough reminds everybody that the probability of a major earthquake on the fault remains very low. But very low is still nonzero, and this morning’s quake and aftershocks mark the very spot down by the Salton Sea that was revealed, through the wonders of paleoseismology, to be at the southern end of a stretch that's just about due for a catastrophic rupture. It’s always wise to be prepared.

Water. Food. Cash in small bills.

You can observe freshly reported quake activity on the U.S. Geological Survey’s Web site, and also watch a probable scenario of a quake move through various Southern California’s urban areas, from the desert to the coast, in a series of cool animations.