It has been about three centuries for the reason that final nice earthquake on the southern San Andreas Fault, probably the most treacherous seismic hazard in California. For a long time researchers have puzzled over why it has been so lengthy. The common interval of enormous earthquakes alongside that portion of the fault has been 180 years over the previous 1,000 years.

While seismologists agree that Southern California is due for the Big One, a gaggle of researchers revealed a paper on Wednesday within the journal Nature that provides a motive for the interval of seismic silence alongside the southern San Andreas, the tension-wracked assembly level of the North American and Pacific tectonic plates.

The principle hinges on the concept whereas the friction of tectonic plates is the first driving power behind earthquakes, there are different components, together with the burden of enormous our bodies of water. Building on prior analysis, the scientists drew a hyperlink between the incidence of enormous earthquakes and the filling of a lake that has grown and ebbed throughout the centuries.

“We are not trying to predict any earthquake that is going to happen in the future, but we might be able to say why we haven’t had one in the last 300 years,” mentioned Ryley G. Hill, a Ph.D. candidate within the division of geological sciences at San Diego State University and the Scripps Institution of Oceanography in La Jolla, Calif.

Mr. Hill and his co-authors discovered that main earthquakes alongside the southern San Andreas fault tended to occur when a big physique of water, Lake Cahuilla, was filling or was full with water from the Colorado River in what at the moment are the Coachella and Imperial valleys.

The lake has drained over the past three centuries and all that continues to be is the vestigial Salton Sea. The authors of the paper imagine that the method of the traditional lake’s emptying and disappearance stabilized the fault to a sure diploma.

Lucy Jones, a seismologist and the chief scientist on the Dr. Lucy Jones Center for Science and Society, known as the reason a “plausible reason for the current long interval since the last earthquake.”

But the analysis, she mentioned, “does not make me want to say don’t worry about the next one.”

Dr. Jones was not concerned within the examine.

Seismologists say that one of many penalties of the three-century interval for the reason that final huge earthquake, outlined as having a magnitude of seven or larger, is that extra stress has constructed up as the 2 grinding tectonic plates have moved in reverse instructions.

“It’s accumulated a large amount of energy analogous to a taut rubber band,” Belle Philibosian, a analysis geologist with the U.S. Geological Survey within the San Francisco Bay Area. “We should be anticipating that the rubber band could snap at any time.”

The southern San Andreas, a part of a community of faults that run throughout California, has probably the most potential for destruction due to the massive quantity of people that dwell within the space — 10 million individuals in Los Angeles County alone. The Northridge earthquake in Los Angeles in 1994, with a 6.7 magnitude, killed greater than 70 individuals and led to $20 billion in injury. It was brought on by one of many many faults that make up the broader San Andreas system, however not by the primary San Andreas Fault that’s the longest in California and is able to a way more highly effective occasion.

The analysis revealed in Nature, which builds on a paper on which Dr. Philibosian was a author in 2011, raises questions on plans to rehabilitate elements of the Salton Sea, which was fashioned when an irrigation canal burst within the early 1900s. Today it’s extremely polluted and shrinking, counting on runoff from close by farm irrigation for water. As the ocean dries out, poisonous mud is left behind and blown into the air, posing a hazard for close by residents.

Impounding extra water within the Salton Sea might tamp down the mud. Recent concepts have included importing desalinated seawater — which a panel rejected last year — and paying farmers to divert their Colorado River allocations. But a significant change within the water stage might additionally set off seismic exercise, based on Dr. Philibosian.

“This earthquake will happen eventually — probably sooner rather than later — no matter what we do,” she mentioned.