August 24, 2007

Report predicts quakes 15 times bigger than 1994 Northridge temblor
Daily News Wire Services

The Southland may be in the midst of a prolonged seismic lull, but once it ends metropolitan Los Angeles will suffer bigger, more frequent temblors, up to 15 times larger than the 1994 Northridge earthquake, according to research published today.

Geologists reached some of their conclusions by examining the size and frequency of quakes going back 12,000 years, finding patterns of heavy and lighter seismic activity every 1,000 to 1,500 years.

In a paper to be published today in the journal Geology, the scientists from the Southern California Earthquake Center argue that when the lull ends, metropolitan Los Angeles will experience significantly bigger and more frequent temblors - up to 15 times larger than the destructive Northridge earthquake of 1994.

That could be soon - or 500 years from now.

"We've been having fewer earthquakes than our long-term average," said James Dolan, a USC geologist and the lead author on the paper. The paper was co-written with geologists David Bowman of Cal State Fullerton and Charles Sammis of USC.

Even more dramatic is the geologists' explanation - welcomed by some scientists and questioned by others - of why the lull is occurring.

The three theorize that two of the region's most active fault zones are essentially taking turns producing earthquakes, with faults in the Mojave Desert producing bigger and more frequent quakes, while faults under Los Angeles take a break, and vice versa.