Salton Sea - Earthquake Geology

Earthquake Geology

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. American researchers 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 the year 1700. Computer models suggest that the normal faults in the area are most vulnerable to deviatoric stress loading by the in-filling of water. Currently, a risk still exists for an earthquake of magnitude 7 or 8. Simulations also showed that 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 approximately 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 that the lake surface elevation reached levels 10–12 metres above sea level in the 1500s.