300-Quake 'Storm' Rattles California Trailer homes knocked off foundations, residents rattled By Mary Papenfuss, Newser User Posted Aug 27, 2012 12:03 AM CDT Updated Aug 27, 2012 3:25 AM CDT 19 comments Comments Map shows eathquake swarm that rattled southern California yesterday. (USofA95jdh) (Newser) – Some 300 earthquakes shook up Southern California in less than nine hours yesterday, and were continuing late into the night. The "quake storm" was centered in rural Imperial County near San Diego. Most temblors were minor, but at least three hit magnitudes above 5.2. Windows were shattered and trailer homes were shaken off their foundations, reports AP, but no other major damage was immediately reported. "Obviously, all this activity is related or interconnected, but it doesn't really follow the typical main shock, aftershock activity," a US Geological Survey seismologist told the Los Angeles Times. The last major quake swarm in the area occurred seven years ago. Seismologists don't completely understand what causes the phenomenon, but the region is at the intersection of the Imperial and San Andreas faults. “It’s been pretty bad," said a Brawley resident who felt 15 quakes in less than three hours. "Some of them are slow, and then they get intense. We’re so anxious right now we can’t sit still.” Brawley Mayor George Nava added: "We're all on edge here. It's not uncommon for us to have earthquakes, but at this frequency and at this magnitude, it's fairly unusual."