Big earthquake a '99.9 percent' certainty on Los Angeles fault, JPL scientist's study says
This is a shake map from 5.1-magnitude earthquake that struck near La Habra on March 28, 2014.
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or near the same faults that caused the March 28, 2014 La Habra quake in the San Gabriel Valley, according to an as-yet-unpublished study by a JPL seismologist.
And a much larger earthquake of magnitude 6 or above has a 35 percent chance of happening along 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, an "abstract" or summary of which was published Oct. 1 and revised on Oct. 7 on the online Earth and Space Science website, was authored by Jet Propulsion Laboratory seismologist 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."
JPL officials in La Canada Flintridge have declined to make the full study public, saying that it will be announced in a press release "within the next day or two." They also declined to comment on the study before making it public.
In advance of the study's release, seismologists at JPL, which is operated by Caltech for NASA, requested a meeting with legislative staff in Sacramento just as the Assembly and state Senate were heading into their autumn recess last month.
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 that 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.
http://www.presstelegram.com/general-news/20151020/big-earthquake-a-999-percent-certainty-on-los-angeles-fault-jpl-scientists-study-says
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