Shake, rock and roll

Seismologists in California were busy this week fighting rumors apparently floating on Twitter that a major earthquake was likely in the next few days.

Officials at Caltech say that rumor is not true -- and that no such prediction can be made.

But researchers say there has been an uptick in earthquakes this year.

The number of earthquakes greater than magnitude 4.0 in Southern California and Baja California has increased significantly in 2010. There have been 70 such quakes so far this year, the most of any year in the last decade. And it's only April. There were 30 in 2009 and 29 in 2008.

Seismologists said they are studying the uptick but cannot fully explain it. Major earthquakes tend to occur in cycles, and experts have said the region in recent years has been in a quiet cycle when it comes to sizable temblors.

I've been watching the USGS map for southern California for some time and have watched swarms of little earthquakes come and go. Fascinating, but I understand how trying to 'predict' an earthquake is nigh impossible. Just look at the 7.2 in Mexico and all the fore and aftershocks. We still don't know much except that the continent is being shoved west over the subduction zone being shoved east, the area is fractured and refractured with faults running across each other. The only thing geologists can predict is that we will get earthquakes constantly. Big and small.

So be prepared.

Bottled water, canned food, batteries

Emergency contacts, flashlights... It might be time to rock and roll, California!:

Scientists are watching closely to see if small faults crossing under the Salton Sea are transferring energy to the larger, more dangerous San Andreas fault after a series of small quake swarms in the area.

The quakes appeared to be tapering off by Monday afternoon, according to the monitoring system run by the U.S. Geological Survey and Caltech. But in a 48-hour period starting Saturday morning, 42 quakes shook just south of Bombay Beach on the Salton Sea. The quakes ranged in magnitude from 0.5 to 3.3, with three larger than 3.0 hitting the area Saturday afternoon.

[snip]

Scientists are particularly interested in the area because an earthquake that starts in Bombay Beach and ripples northwest along the San Andreas fault could be the Big One that devastates Los Angeles, said Graham Kent, a research geophysicist at UC San Diego.

These quakes appear to be taking place at the hazy intersection of several recently mapped faults crossing beneath the Salton Sea and the the San Andreas fault.

The worry for scientists comes from a case in 1987, when a magnitude-6.2 earthquake on one of the crossing faults appeared to trigger a 6.6 quake 12 hours later on the Superstition Hills fault to the south. The San Andreas fault is north of these crossing faults and the geometry is similar, Kent said.

This swarm, he said, "is a flashing yellow light that tells you to be prepared and to spend some time trying to understand the significance."

Here's a California earthquake map that notes recent activity.