Did the earth move for you?

In case you haven't heard (or live any where but SoCal) we've been experiencing a series of small earthquakes over the last two weeks. Generally they're only big enough to rattle nerves, but Thursday morning's 4.4 shaker did some minor damage, breaking dishes and scaring the hell out of the cat. It was the strongest quake I've felt in the Fontana area and I've lived here all my life. Monitoring the scanner on the way to work, I overheard the cops at Ontario International Airport discussing minor damage, such as light fixtures, etc., that fell down.

The first article explains what happened (I was one of the thousands who hit up the web to see how bad things were) while the second article, on earthquake predicting, is less reassuring.

After ground shakes, many go online for information

WEB SITE: Instant info on seismic activity is there, and residents can report their experiences.

07:20 AM PST on Friday, January 7, 2005

By HENRI BRICKEY / The Press-Enterprise

Within minutes of the 4.4 earthquake that struck north of Fontana early Thursday, seismologists in Colorado were reviewing firsthand accounts from Southern Californians who experienced the shaking.

By 5:30 p.m., more than 3,200 people from 355 ZIP codes had filed their impressions on an Internet site set up by seismologists.

Launched five years ago, the site - http://pasadena.wr.usgs.gov/ - provides nearly instant information on earthquakes as well as collects reports from the public. The U.S. Geological Survey and the California Institute of Technology sponsor the Web site.

"This is one of the most sophisticated citizen science programs out there," said David Wald, a seismologist with the National Earthquake Information Center in Golden, Colo.

Information from seismic monitoring equipment - about 350 sensors in Southern California alone - is automatically sent to the Web site. Earthquakes, even tiny ones less than magnitude 1.0, generally show up within 5 minutes on an interactive map. Site visitors can get details on epicenter, magnitude and other characteristics of the quake. They also can fill out a questionnaire, about how a quake felt.

Responses are catalogued and used to create a map showing the strength of the shaking in various areas. Scientists use the information, in part, to help confirm that ground sensors are reporting accurately when earthquakes strike, Wald said.

Getting people to tell about the quakes they experience has other advantages, according to Wald. "People use this as a catharsis. You want to tell people how you felt after experiencing an earthquake.

"It takes a little bit of the mystery out of Mother Nature."

Initially, the system was limited to Southern California, he said. The network has since expanded across the United States and throughout the world.

"The feedback and response is mind boggling," said Wald, who developed the "Did You Feel It?" monitoring system while working in the Geological Survey's Pasadena office. "We're always astonished at how many answers come in."

More than 17,000 people responded after a 4.4 magnitude earthquake in Virginia, he said.

If the system had been in place in 1994 when a 6.7 quake hit Northridge, officials would have known instantly that neighboring communities also had damage.

Fire Marshal Mike Hatfield, Cathedral City's emergency services coordinator, said his department looks at Web sites, monitors amateur radios and uses other resources to determine the extent of damage caused by earthquakes in outlying areas.

Rift develops over quakes' significance

By L.C. GREENE, Staff Writer

The swarm of small tremors in the Fontana-Rialto area that rattled good crystal and bad nerves early Thursday came as no surprise to a group of earthquake forecasters at Jet Propulsion Laboratory in La Canada Flintridge.

"It was on a hot spot,' said Andrea Donnellan, principal investigator for JPL's QuakeSim project.

The seismic team's forecast map for California shows areas likely to experience 5.0-magnitude or greater quakes over a 10-year period.

Since 2000, 30 of the 38 major earthquakes around the world have hit in QuakeSim team hot spots.

"We've had a significant amount of success forecasting the location of major earthquakes,' said team member John Rundle, director of the UC Davis Center for Computational Science and Engineering.

However, while not writing them off, Caltech seismologist Lucy Jones questioned the usefulness of QuakeSim's long-range predictions, since the team's mapped hot spots coincide with known earthquake zones.

"Maybe they just put (the hot spots) where you're going to have earthquakes anyway,' she said.

The QuakeSim team might do well to test its system to see whether it contributes something more than what is already known, Jones said.

Thursday's quakes in the Fontana-Rialto area the strongest of which was magnitude 4.4 and reportedly was felt as far west as Los Angeles' Fairfax district and as far south as Orange County didn't count toward the QuakeSim team's California forecast, which is based on larger tremors.

However, "it means the stress is being reduced,' Donnellan said.

The cluster of Fontana quakes will be included in ongoing calculations.

The small shakers occurred very near the large and historically active San Jacinto Fault, which runs from the Fontana-Rialto area through Loma Linda and on to points south.

While Thursday's quakes might have relieved a little stress, it's well known that the northern end of the San Jacinto Fault remains overdue for a major earthquake of 6.0 or greater, Donnellan said.

That bigger quake could occur by Aug. 14, said another group of earthquake predictors.

"We have reason to believe the probability of a strong earthquake in the area is increasing,' said Vladimir Keilis-Borok of UCLA, who heads a team of scientists from the United States, Russia, France and Italy.

However, the 82-year-old Russian-born seismologist and mathematical geophysicist cautions the team's forecasts are only a kind of test, to see whether the forecasting methods actually work.

These scientific data crunchers warned of a major quake last year for a broad section of the Southern California desert. It didn't happen.

However, in July 2003, the Keilis-Borok-headed team predicted a magnitude-7 or greater quake in a region around Hokkaido, Japan, by Dec. 28 of that year. On Sept. 25, 2003, a magnitude-8.1 quake rocked Hokkaido.

While Tuesday's quake swarm in the Fontana-Rialto area wasn't calibrated into the latest forecast, Keilis-Borok found the tremors interesting.

Such swarms are "a more rare event,' he said.

The difference between the Keilis-Borok experimental predictions and the QuakeSim forecasts involves both time and territory.

QuakeSim hot spots tend to be very specific areas, with the forecasts covering 10-year time spans. The Keilis-Borok time spans run over months, with targeted areas that are broader, typically covering hundreds of miles.

The Keilis-Borok team has yet to produce sufficiently consistent results, meaning the approach remains an open question, Jones said.

What successes the team claimed may have amounted to no more than random luck, she said. As for its method, "I hope it's true,' she added.

Only time will tell. And Aug. 14 is still seven months away.