Los Angeles residents may want to prepare their earthquake kits. A team of researchers from NASA's Jet Propulsion Laboratory (JPL) reports there is a 99.9 percent chance that an earthquake with at least a 5.0 magnitude will hit the area within the next two and a half years.
For their study published in Earth and Space Science on Sept. 30, JPL geophysicist Andrea Donnellan and colleagues used radar and GPS to measure the surface deformation in the Earth's crust produced by the March 28, 2014 La Habra 5.1 earthquake, which was centered between the Whittier and Puente Hills Faults.
Donnellan explained that, when the La Habra tremor struck, it relieved some of the stress in the fault system and moved some of the upper sediments in the LA basin.
The researcher, however, pointed out that those strains have enough power to set off an ever larger earthquake in the same epicenter, with Donnellan estimating the energy stored is still enough to produce about a 6.1 to 6.3 magnitude earthquake.
The researchers looked at the earthquakes that struck the region over the past eight decades and found 32 cases with a 5.0 magnitude. From this, they were able to estimate the likelihood of a sizable earthquake hitting Southern California.
"We didn't do a prediction. We were looking at the elastic energy stored in the crust," Donnellan said. "It's like silly putty. If you pull it, it stretches, and then it breaks. The Earth behaves the same way."
The findings reveal the probability of a quake similar to the La Habra earthquake striking the entire 60-mile radius of the Los Angeles area is high, with results showing a 99 percent probability that a magnitude 5.0 or stronger quake would rock Los Angeles within three years.
Seismologists at the U.S. Geological Survey (USGS), which also conducts studies of quake risks in California, questioned the research team's predictions, albeit they also have high probability figures. Based on the models they use, the USGS experts said that the likelihood of a magnitude 5.0 or 6.0 earthquake striking the region over a three-year period is 85 percent.
"The area — a 100 km radius circle centered on the city of La Habra — is a known seismically active area. For this same area, the community developed and accepted model of earthquake occurrence, 'UCERF3,' which is the basis of the USGS National Seismic Hazard Maps, gives a three-year probability of 85 percent," the USGS said. "In other words, the accepted random chance of an M5 or greater in this area in three years is 85 percent, independent of the analysis in this paper."
Photo: Ron Reiring | Flickr
