According to scientists with NASA’s Jet Propulsion Laboratory in Pasadena, a new study indicates that the Los Angeles Area has a 99.9 percent chance of experiencing an earthquake magnitude 5.0 or greater in the next three years.
Results of the study, titled “Potential for a large earthquake near Los Angeles inferred from the 2014 La Habra earthquake,” published on October 1 in the American Geophysical Union’s Earth and Space Science journal by a team of NASA geophysicists led by Dr. Andrea Donnellan, has sparked a controversy among seismologists.
The team of scientists said they estimated the chances of a major earthquake in a 60-mile radius of the L.A. area of Southern California in the next three years using airborne radar data and GPS measurements.
The measurement results showed that the area has a 99.9 percent chance of a magnitude 5.0 earthquake or greater in the next three years, the researchers said.
Donnellan explained that the recent La Habra earthquake that occurred in the spring of 2014 only relieved some of the stress in the faults. There remains enough pent-up seismic energy waiting to be released, and it could trigger a stronger quake within a 60-mile radius of the epicenter of the last earthquake.
“When the La Habra earthquake happened, it was relieving some of that stress, and it actually shook some of the upper sediments in the LA basin and moved those a little bit more,” Donnellan told CBS Los Angeles.
“There’s enough energy stored to produce about a magnitude 6.1 to 6.3 earthquake,” she added.
Evidence that the earthquake relieved only part of the overall stress in the crust came partly from the fact that the deformation caused by the quake was larger than expected for a 5.1 magnitude event.
The researchers said in their study that, “The shallow ground movements observed from this [La Habra] earthquake likely reflect strain accumulated on deeper faults, which remain locked and may be capable of producing future earthquakes.”
But seismologists with the U.S. Geological Survey have raised questions about the estimation by the JPL team.
In statement posted to its Facebook page, USGS criticized the work of the JPL team, saying that the published study does not provide sufficiently detailed explanation about how the researchers arrived at the 99.9 percent estimation.
USGS noted that the currently accepted estimate of the probability of a magnitude 5.0 earthquake or greater in the next three years is 85 percent.
“… the accepted random chance of a (magnitude five) or greater in this area in three years is 85 percent, independent of the analysis in this paper.”
USGS also said the published paper has not yet been reviewed by the National Earthquake Prediction Evaluation Council which reviews scientific forecasts and predictions of earthquakes.
The statement went on to explain that the generally accepted estimate of 85 percent was reached using “community developed and accepted model of earthquake occurrence, “UCERF3″ (Uniform California Earthquake Rupture Forecast, Version 3), which is the basis of the USGS National Seismic Hazard Maps.”
“The earthquake rate implied by the 99.9% probability is significantly higher than observed at any time previously in Southern California, and the lack of details on the method of analysis makes a critical assessment of this approach very difficult. Therefore, the USGS does not consider the analysis presented in this paper a reason to change our assessment of the hazard.”
According to 89.3 KPCC, Lucy Jones, with the USGS, said, “This is the opinion of a small group of scientists — it has not been reviewed for action as a prediction, and I wouldn’t be changing any behavior on the basis of this study.”
But even the estimation of 85 percent probability of a sizable earthquake in the L.A. area in the next three years that the USGS accepts is very high.
There is consensus among seismologists that residents of the area need to be prepared.
[Image via USGS/Facebook]