Three scientists at Scripps Institute of Oceanography co-authored a study published on Sunday that said floods that used to flow into what is now the Salton Sea might be linked to earthquakes on the southern portion of the San Andreas fault.
Interference with Colorado River floods that regularly flowed into what used to be the Salton Sink may have “stopped the clock” on a regular series of big earthquakes, setting the stage for a 7.5 or higher megaquake that could devastate Southern California, the scientists found.
The findings were published in the journal Nature Geoscience, and were first reported by The San Diego Union-Tribune’s signonsandiego.com web site.
The seismically active southern end of the San Andreas Fault Zone lies under the Salton Sea, a wide depression whose bottom is about 250 feet below sea level. The area was regularly flooded by the Colorado River over the relatively recent millennia, a practice that ended 100 years ago when levees were built to force the Colorado to flow into the Sea of Cortez just south of Yuma, Ariz.
Because of that diversion, the construction of upstream dams near Las Vegas and regional droughts, the Colorado has stopped flooding into the Imperial Valley and Salton Sink, a dry lakebed that was transformed into the Salton Sea after gigantic floods in 1906. The Colorado last flooded and reached the Sea of Cortez in 1982, but it now trickles into the sand about where the San Andreas fault crosses the border 155 miles east of San Diego.
The Scripps researchers who co-authored the study were Neal Driscoll, Debi Kilb and Karen Luttrell. Other researchers on the project came from the U.S. Geological Survey and the University of Nevada, Reno. The results show:
- That several once unknown fingers of the San Andreas system sit beneath the Salton Sea, and the sand and dirt of the Imperial Valley.
- The faults let loose with magnitude 7.0 quakes or larger every 180 years until the early 20th century — the same time the Colorado floods that had brought billions of pounds of water to the area were staunched.
- That the Colorado River flooding may have affected the timing of the smaller, stress-relieving faults.
The study covers the area just north of the zone struck by the 7.2 magnitude Mexicali Easter Sunday quake last year. It killed two people in Mexico, and was felt as a nasty sway in San Diego County, all the way up to Los Angeles.
City News Service contributed to this report.