No significant earthquakes of magnitude seven or greater have hit Southern California for three decades despite its many faults parallel to the San Andreas. Many believe that the giant ancient Lake Cahuilla or its remnant Salton Sea has something to do with this.
San Andreas Fault and Southern California
Everywhere in Southern California, you will find faults. Some parallel the San Andreas fault system; others extend in the opposite direction. Faults are running through Hollywood and immediately right offshore. Ultimately, the greatest risk to the residents is much closer to home, depending on where the earthquake occurs along the San Andreas fault.
"Here in L.A., a lot of the risk is the fault right underneath us," said John Vidale, an earthquake researcher at the University of Southern California who had no role in the research. "We have a lot of risks, and many of them aren't from the San Andreas."
The Sand Andreas Fault is located between the boundaries of two separate tectonic plates. Although it is known as California's sleeping monster, the state's greatest earthquakes are caused by it.
The fault resembles a long, thin valley that represents the meeting point of the North American and Pacific plates when viewed from space. According to a study, the drying Salton Sea or the disappearance of Lake Cahuilla may delay the next Big One. Salton Sea's ancient predecessor is now called Lake Cahuilla, which is reportedly 40 times larger in volume than the modern remnant.
According to Thomas Rockwell, a geology professor at San Diego State and co-author of the paper, Lake Cahuilla was so large that it extended from the Coachella Valley south into Mexico and from as far west as Plaster City, California, to as far east as the Chocolate Mountains.
When Lake Cahuilla was full, it rose to roughly 40 feet above sea level and peaked at a depth of more than 300 feet before beginning to overflow once more. In comparison, the Salton Sea today has a maximum depth of roughly 50 feet and a height of about 240 feet below sea level.
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How Does Lake Cahuilla's Disappearance Delay Major Earthquakes?
Researchers discovered a trend where huge earthquakes would often precede the lake's periodic drying up when Colorado River waters poured into Lake Cahuilla. It is estimated that over the last millennium, Lake Cahuilla was full six times -- approximately between 930 and 966, 1007 to 1070, 1192 to 1241, 1486 to 1503, 1618 to 1636, and 1731 to 1733.
According to Rockwell, they determined that the majority of earthquakes have happened when lakes are present by examining the history of earthquakes and their relationship to the lakes."
Six of the seven significant earthquakes that the researchers discovered happened either as Lake Cahuilla was peaking or filling up.
The recent earthquake history implies that all lake-filling periods were followed by significant earthquakes, even though earlier research regarding the temporal correlation between earthquakes and lake episodes over the past millennium was equivocal. The time of the earthquake and the lake appear correlated, which is likely not accidental.
Without the massive lake straining the San Andreas and making the fault more susceptible to the big one, the impending large earthquake in Southern California, which might result in around 1,800 fatalities, $200 billion in damage, and immense disruption, is reportedly delayed.
Research geologist Belle Philibosian of the U.S. Geological Survey, who was not involved in the study, cautioned that although the Salton Sea is drying up, earthquakes will still occur and pose a risk to the local population.
"Even if the Salton Sea dries up completely, that next southern San Andreas earthquake is still going to happen. And we still need to be prepared for it," Philibosian said.
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