Research ArticleSeismology

A case for historic joint rupture of the San Andreas and San Jacinto faults

Science Advances  11 Mar 2016:
Vol. 2, no. 3, e1500621
DOI: 10.1126/sciadv.1500621

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The San Andreas fault is considered to be the primary plate boundary fault in southern California and the most likely fault to produce a major earthquake. I use dynamic rupture modeling to show that the San Jacinto fault is capable of rupturing along with the San Andreas in a single earthquake, and interpret these results along with existing paleoseismic data and historic damage reports to suggest that this has likely occurred in the historic past. In particular, I find that paleoseismic data and historic observations for the ~M7.5 earthquake of 8 December 1812 are best explained by a rupture that begins on the San Jacinto fault and propagates onto the San Andreas fault. This precedent carries the implications that similar joint ruptures are possible in the future and that the San Jacinto fault plays a more significant role in seismic hazard in southern California than previously considered. My work also shows how physics-based modeling can be used for interpreting paleoseismic data sets and understanding prehistoric fault behavior.

  • San Andreas Fault
  • San Jacinto Fault
  • fault interactions
  • California earthquakes
  • earthquake physics
  • earthquake modeling
  • interpretation of paleoseismic data
  • southern California earthquake hazard
  • historic earthquakes
  • multi-fault rupture

This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial license, which permits use, distribution, and reproduction in any medium, so long as the resultant use is not for commercial advantage and provided the original work is properly cited.

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