Late-Holocene earthquake and sedimentary histories beneath the Salton Sea, California: relationship between lake flooding and fault rupture

Daniel S. Brothers, Neal W. Driscoll, Graham M. Kent, Alistair J. Harding, Jeff M. Babcock, & Robert L. Baskin

Under Review 2010, SCEC Contribution #1348

Marine paleoseismic investigations in the Salton Sea imaged a system of ~N15°E oriented normal faults with vertical slip rates ranging from 1.1 to 3.4 mm/yr and average earthquake
recurrence intervals of 115 to 460 years. Age estimates for the upper six Lake Cauhilla parasequences (~830 AD - present) were obtained by correlating acoustic stratigraphy in the Salton Sea with CPT borings and onshore radiocarbon dated sequences. Based on the relationship between flooding
surfaces and displacements across the normal faults, it appears that some ruptures on the three main hinge zone faults occur when the Colorado River floods the basin. Flooding of Lake Cauhilla increases both the vertical load and pore pressure on each normal fault making them more inclined to fail than nearby strike-slip fault systems. Assuming strain is released seismically, faults in the Salton Sea can potentially generate M6-6.6 earthquakes, which could act as stress modulators on the southern San Andreas Fault. Two of the last five events on the southern San Andreas Fault correlate with events observed on the normal faults offshore.

Citation
Brothers, D. S., Driscoll, N. W., Kent, G. M., Harding, A. J., Babcock, J. M., & Baskin, R. L. (2010). Late-Holocene earthquake and sedimentary histories beneath the Salton Sea, California: relationship between lake flooding and fault rupture. Bulletin of the Seismological Society of America, (under review).