A cluster of more than 200 small earthquakes beneath the Salton Sea in Southern California earlier this week has scientists waiting to see if the slumbering San Andreas fault nearby could be the next to move. The U.S. Geological Survey estimates that following the quake swarm at the Salton Sea on Monday and Tuesday, the likelihood of a magnitude-7 or greater earthquake being triggered is as high as 1 in 100 over the next seven days, though the odds will lower as time goes on.

But for now, local seismologists might feel their hearts racing. "When there's significant seismicity in this area of the fault, we kind of wonder if [the San Andreas] is somehow going to go active," Caltech seismologist Egill Hauksson told the Los Angeles Times. "So maybe one of those small earthquakes that's happening in the neighborhood of the fault is going to trigger it, and set off the big event."

And by big event, they mean big:

A San Andreas earthquake starting at the Salton Sea has long been a major concern for scientists. In 2008, USGS researchers simulated what would happen if a magnitude-7.8 earthquake started at the Salton Sea and then barreled up the San Andreas fault, sending shaking waves out in all directions. By the time the San Andreas fault becomes unhinged in San Bernardino County's Cajon Pass, Interstate 15 and rail lines could be severed. Historic downtowns in the Inland Empire could be awash in fallen brick, crushing people under the weight of collapsed buildings that had never been retrofitted. Los Angeles could feel shaking for a minute — a lifetime compared with the seven seconds felt during the 1994 Northridge earthquake. Shaking waves reach as far as Bakersfield, Oxnard, and Santa Barbara. About 1,600 fires spread across Southern California. And powerful aftershocks larger than magnitude-7 pulverize the region, sending shaking into San Diego County and into the San Gabriel Valley. [Los Angeles Times]

Scientists say major earthquakes happen in Southern California about once every 150 or 200 years; the last big quake at the Salton Sea-tip of the San Andreas fault was 330 years ago. Read the full chilling report at the Los Angeles Times. Jeva Lange