The “probability is 99.9 percent” that an earthquake measuring 5.0 or greater will occur within the next two and a half years on or near the same faults that caused the March 28, 2014 La Habra quake in the San Gabriel Valley, according to a study by a JPL geophysicist. 

And a much larger earthquake of magnitude 6 or above has a 35 percent chance of happening along or near the same fault lines in that time frame, the study says.  The quake could occur anywhere within 100 kilometers — about 60 miles — of the 2014 quake, the study says. 

The study that was published Oct. 1 and revised on Oct. 7 on the online Earth and Space Science website, was authored by Jet Propulsion Laboratory’s Andrea Donnellan along with a number of other earthquake scientists under the headline “Potential for a large earthquake near Los Angeles inferred from the 2014 La Habra earthquake.” 

A seismologist at Caltech, who read the study on Tuesday, cautioned against earthquake predictions, saying it isn’t an exact science and making such claims can cause “fear and confusion.” 

“As far as I’m concerned there has never been a successful earthquake prediction and a scientific breakthrough would be required for us to make a scientifically based prediction,” Thomas Heaton, professor of engineering seismology and director of the Earthquake Engineering Research Laboratory at Caltech said after reading the study. “ 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.  That said, earthquakes tend to cluster in time and space, and the fact that there have been recent events in the La Habra area tells us that there is a reasonable likelihood that there will be more.” 

JPL officials in La Canada Flintridge said Tuesday that an updated version of the study would be released soon to the public.  They declined comment on the study Tuesday. 

In advance of the study’s release, seismologists at JPL, which is operated by Caltech for NASA, scheduled a meeting with legislative staff in Sacramento just as the Assembly and state Senate were heading into their autumn recess last month.  The meeting is scheduled for next week. 

The La Habra quake in 2014 was magnitude 5.1 and caused what the Donnellan study calls “a surprising amount of damage” to local homes and businesses in the southeastern San Gabriel Valley.  The study says the earthquake “occurred between the right-lateral strike-slip Whittier fault and the Puente Hills thrust fault” and that a similar quake as large as 6.3 in scale in the near future “could occur on any or several of these faults, which may or may not have been identified by geologic surface mapping.” 

The Puente Hills fault runs from the Whittier area northwest to just south of Griffith Park in Los Angeles, and was responsible for the 1987 Whittier Narrows quake, a 5.9 temblor that killed three people.  The Whittier Fault runs along the Chino Hills range between the cities of Chino Hills and Whittier. 

Earthquake scales, including the one formerly known as the Richter scale, named after Caltech seismologist Charles Richter, vary in their descriptions between “magnitude” and “intensity.”  They rise logarithmically rather than arithmetically, so that higher numbers describe vastly greater seismic events than lower ones.  In general, 5.5 to 6.0 quakes are known to cause light damage to buildings and other structures, whereas those that rank 6.1 to 6.9 may cause a lot of damage in very populated areas.  The Loma Prieta quake in the Bay Area in 1989 measured 6.9 and caused 63 deaths.  The Northridge earthquake in 1994 measured 6.7 and caused 57 deaths. 

Study author Andrea Donnellan is a principal research scientist at JPL, and adjunct assistant professor of research in earth sciences at USC.  She is president-elect of the American Geophysical Union’s Nonlinear Geophysics Focus Group.  She received her doctorate in geophysics at Caltech in 1991.