Earthquake 'super-cycle' patterns on the Garlock fault

April 22, 2015
Seismogram being recorded by a seismograph at the Weston Observatory in Massachusetts, USA. Credit: Wikipedia

A new look at slip rate data and geologic evidence for ancient earthquakes on the central Garlock fault suggest that seismic activity along the fault may be controlled in part by "super-cycle" changes in strain that occur on thousand-year timescales.

The findings are part of an increasing body of evidence that suggests there may be large-scale coordination of earthquakes in time and space, which can cause large earthquakes to cluster in time along a single fault system, for instance. The Garlock fault runs along the northern border of the Mojave Desert in southern California. Although the immediate region around the fault is not heavily populated, earthquakes along the fault could impact most of southern California.

James Dolan of University of Southern California and colleagues' new look at the Garlock fault found that a cluster of four earthquakes during the late Holocene, about 500 to 2000 years ago, occurred at a time when the average slip rate on the fault was twice as fast as the long-term average slip rate. Previous paleoseismic results show, however, that this cluster was preceded by a 3000-year lull of very small or no slip. This "on-off" behavior of the Garlock indicates that the fault may go through "super-cycles" of strain, where the strength of the waxes and wanes over thousands of years, the researchers say. Overall, the cycles in the area may be caused by this type of super-cycle influencing the strength of many different faults in the region, including the San Andreas, Garlock and the Eastern California Shear Zone faults.

Dolan will present his research on April 22 at the annual meeting of the Seismological Society of America (SSA) in Pasadena, Calif.

Explore further: Some sections of the San Andreas Fault system in San Francisco Bay Area are locked, overdue

Related Stories

Hoodoos—key to earthquakes?

February 4, 2013

In the absence of long-term instrumental data, fragile rock formations, called hoodoos, may be key to understanding seismic hazard risk. In this study, researchers consider two hoodoos in Red Rock Canyon region to put limits ...

Seabed samples rewrite earthquake history near Istanbul

March 30, 2015

Located in the Marmara Sea, major earthquakes along the North Anatolian Fault (NAF) system have repeatedly struck what is current-day Istanbul and the surrounding region, but determining the recurrence rate has proven difficult ...

Recommended for you

Researchers pin down one source of a potent greenhouse gas

November 20, 2017

A study of a Lake Erie wetland suggests that scientists have vastly underestimated the number of places methane-producing microbes can survive—and, as a result, today's global climate models may be misjudging the amount ...

Clay mineral waters Earth's mantle from the inside

November 20, 2017

The first observation of a super-hydrated phase of the clay mineral kaolinite could improve our understanding of processes that lead to volcanism and affect earthquakes. In high-pressure and high-temperature X-ray measurements ...

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

Returners
1 / 5 (1) Apr 28, 2015
Sounds like we're gonna have a come to Jesus moment in S. California any time in the next few decades. See linked related article from October last year.
Uncle Ira
not rated yet Apr 28, 2015
Sounds like we're gonna have a come to Jesus moment in S. California any time in the next few decades


I am not S. California non. I am in S. Louisiana. I though you are too. Did they ship you out of state this last time instead of Mandeville?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.