On Oct. 7 a NASA-led team of scientists published a report in the prestigious, peer-reviewed journal Earth and Space Science stating that the greater Los Angeles area – particularly near its subarb of La Habra – has a 99.9% chance of suffering a magnitude 5.0 earthquake within the next 2.5 years.
When the news of this disturbing statistic hit headlines, the US Geological Survey took action. Established in 1979, the USGS has major offices across the country that focus on policies related to Earth sciences including risk from earthquakes and damage from fracking.
In a rare event, the governemnt-run scientific agency published a public statement on Oct. 20 refuting NASA’s report and asserting their own independent estimates, which suggests an 85% probability for a magnitude-5.0 earthquake to hit the same region. The refute reads as follows:
USGS Statement on JPL La Habra Study in the news:
This paper claims a 99.9% probability of an earthquake of magnitude 5 or greater occurring in the next 3 years within a large area of Southern California without providing a clear description of how these numbers were derived. 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 3-year probability of 85%. In other words, the accepted random chance of a M5 or greater in this area in 3 years is 85%, independent of the analysis in this paper.
While the earthquake forecast presented in this paper has been published in the online journal Earth and Space Sciences, it has not yet been examined by the long-established committees that evaluate earthquake forecasts and predictions made by scientists. These committees, the California Earthquake Prediction Evaluation Council, which advises the California Office of Emergency Services, and the National Earthquake Prediction Evaluation Council, which advises the U.S. Geological Survey, were established to provide expert, independent assessment of earthquake predictions.
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.
Scientists at the USGS are not the only ones who questioned the paper’s results. Thomas Heaton, a professor of engineering seismology and the director of the Earthquake Engineering Research Laboratory at Caltech, recently told the San Gabriel Valley Tribune:
“While the authors are credible scientists, this paper does not meet my definition of science. That is, this type of slip deficit has been tried in the past, but it has been shown to have minimal predictive power.”