page_title: Salton Sea
section_title: Earthquakes and tectonic setting
hierarchical_section_title: Salton Sea / Geology / Earthquakes and tectonic setting
caption_attribution_description: English: Aerial view of the Salton Sea from the north-northeast (from over Joshua Tree National Park), looking into the early afternoon sun
context_page_description: The Salton Sea is a shallow, saline, endorheic rift lake located directly on the San Andreas Fault, predominantly in the U.S. state of California's Imperial and Coachella valleys.
  The lake occupies the lowest elevations of the Salton Sink in the Colorado Desert of Imperial and Riverside counties in Southern California. Its surface is 236.0 ft below sea level as of January 2018. The deepest point of the sea is 5 ft higher than the lowest point of Death Valley. The sea is fed by the New, Whitewater, and Alamo rivers, as well as agricultural runoff, drainage systems, and creeks.
  Over millions of years, the Colorado River has flowed into the Imperial Valley and deposited soil, building up the terrain and constantly changing the course of the river. For thousands of years, the river has alternately flowed into and out of the valley, alternately creating a freshwater lake, an increasingly saline lake, and a dry desert basin, depending on river flows and the balance between inflow and evaporative loss. The cycle of filling has been about every 400–500 years and has repeated many times.
context_section_description: The Salton Sea and surrounding basin sits over the San Andreas Fault, San Jacinto Fault, Imperial Fault Zone, and a "stepover fault" shear zone system. Geologists have determined that previous flooding episodes from the Colorado River have been linked to earthquakes along the San Andreas Fault. Sonar and other instruments were used to map the Salton Sea's underwater faults during the study. During the period when the basin was filled by Lake Cahuilla, a much larger inland sea, earthquakes higher than magnitude 7 occurred roughly every 180 years, the last one occurring within decades of 1700. Computer models suggest the normal faults in the area are most vulnerable to deviatoric stress loading by filling in of water. Currently, a risk still exists for an earthquake of magnitude 7 to 8. Simulations also showed, in the Los Angeles area, shaking and thus damage would be more severe for a San Andreas earthquake that propagated along the fault from the south, rather than from the north. Such an earthquake also raises the risk for soil liquefaction in the Imperial Valley region.
  The effective drainage divide that separates the Salton Sea from the Gulf of California is about 9 m (30 ft) in elevation and is located near Delta, northeastern Baja California State, Mexico, south-southeast of Mexicali. Past sea level rise may partially be responsible for the salinity of the lake, while potential future changes in sea levels could occur. However, other factors such as hydrothermal vents, diffusion of salt from minerals and sediment, including concentrated brine, and evaporites are another contributor to salinity, as is the recent lowering of lake levels raising the salinity, though sedimentary records show the lake surface elevation reached levels 10–12 m above world sea level in the 1500s.
caption: Aerial view of the Salton Sea from the north
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