Breaking the Strongest Link Triggered Big Baja Earthquake

UC Davis ^ | 2/15/16 | Becky Oskin

[JimSEA]

spate of major earthquakes on small faults could overturn traditional views about how earthquakes start, according to a study from researchers at the Centro de Investigación Científica y de Educación Superior in Ensenada, Mexico, and the University of California, Davis.

In the past 25 years, many of California’s biggest earthquakes struck on small faults, away from the San Andreas Fault plate boundary. These events include the Landers, Hector Mine and Napa earthquakes. Several of the quakes were unexpected, rattling areas thought seismically quiet.

A closer look at one of the surprise events, the magnitude-7.2 El Mayor-Cucapah earthquake, showed that small faults may often link together along a “keystone” fault. A keystone is the central stone that holds a masonry structure together. During the El Mayor-Cucapah earthquake, the keystone fault broke first, unlocking seven smaller faults, the study found. Cucapah earthquake, the keystone fault was not the one closest to breaking.

[JimSEA]

"One of the important outcomes of this study is you can have a whole network of faults activated together by one underpinning fault, and that’s an important concern,” said study co-author Michael Oskin, a UC Davis professor of geology. “An earthquake involving a system of small faults can be more damaging than a single event because it increases the amount of seismic energy released.”

That is the "money" quote out of the study as it has implications for numerous areas of related small faults at several points along the San Andreas Faault. Much of LA and the Haywood faults spring to mind. The "Big One" could likely be a whole bunch of little ones. Very few areas along the boundary fault can be immune.

[If You Want It Fixed - Fix It]

What about the pull of the moon that lifts tidal waters - couldn’t it also lift land mass enough to unhitch a couple of stuck plates...just enough? How about THAT for a head scratcher?!

Really!

[JimSEA]

It certainly might give some repetitive stress but the tectonic movements really build up incredible stress. Imagine the force involved in moving these massive blocks.