SCEC Award Number 08127 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Constraining Fault Architecture and History in the Salton Sea: Processing CHIRP Seismic Data and Acquiring Vibra-Cores.
Investigator(s)
Name Organization
Neal Driscoll University of California, San Diego Graham Kent San Diego State University Gordon Seitz San Diego State University
Other Participants
SCEC Priorities A1, A6, A9 SCEC Groups SHRA, SoSAFE
Report Due Date 02/28/2009 Date Report Submitted N/A
Project Abstract
 The southernmost San Andreas fault appears poised for a large-magnitude earthquake, since its present period of dormancy is nearly twice as long as the average recurrence interval. Forecasting of future earthquakes is difficult based on short-term strain accumulation observations because their link to the process of strain release is not well established. In order to gain insights into the potential and character of the next large earthquake, researchers at Scripps/UCSD and San Diego State University are studying the history of earthquake rupture of the southern San Andreas Fault and the Brawley
Seismic Zone (BSZ) using an integrated onshore/offshore approach. Regionally deposited lacustrine sediments, provide a high-resolution, 1200-yr-long record of rupture at Salt Creek and an even longer history of rupture beneath the Salton Sea, including the unexpected observation of significant ground rupture within the BSZ. Potential correlations between onshore and offshore lacustrine deposits using paleoseismic excavations and recently collected high-resolution seismic CHIRP imagery (Spring, 2006 & 2007), may provide new insights into the rupture dynamics between southernmost San
Andreas and cross-faults within the BSZ. The identification of large-magnitude ruptures within the BSZ, potentially coincident in time with movement along the southern San Andreas, raises the possibility of strain release or triggering within the BSZ, resulting in a northward propagation of rupture. Numerical simulations suggest such a south-tonorth scenario of rupture along the southern San Andreas would increase shakingrelated
damage in the Los Angeles basin. What is presently lacking is a robust
chronostratigraphic framework that will enable a direct comparison between recent southern San Andreas ruptures, and large earthquakes along cross-faults and normal faults imaged beneath the Salton Sea. Here we propose two distinct yet complementary tasks: (1) provide 6 months of student support to analyze over 400 km of seismic CHIRP profiles, and (2) collect several 10 m vibra-cores using a custom, light-weight system developed at Costal Carolina University that can be used on a 55’ pontoon boat, with minimal lifting capabilities. Radiocarbon C-14 dating of these cores will help establish a robust chronostratigraphic framework to explore cross- or normal-fault triggering of southern San Andreas Fault earthquakes.