SCEC Award Number 12067 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title 1987 SUPERSTITION HILLS EARTHQUAKE: A TRIGGERED EVENT WITH A COMPLEX NUCLEATION AND RUPTURE DYNAMICS
Investigator(s)
Name Organization
Ralph Archuleta University of California, Santa Barbara
Other Participants Qiming Liu
SCEC Priorities 2b, 2d, 6e SCEC Groups FARM, Seismology, CS
Report Due Date 03/15/2013 Date Report Submitted N/A
Project Abstract
 We examine whether the Elmore Ranch earthquake, and its associated aftershocks, might have triggered the Superstition Hills Fault earthquake. We show that the Elmore Ranch earthquake could have dynamically triggered the Superstition Hills Fault earthquake if the slip weakening distance were less than 0.061 m on the Superstition Hills Fault.
Intellectual Merit How and why one earthquake triggers another is fundamentally important to our understanding of the conditions for which an earthquake can nucleate. In one sense an earthquake might be thought of as a continuous cascade of triggers. Similarly aftershocks are triggered events, but what mechanism allows for the delay remains unknown.
Broader Impacts Earthquake triggering is a common occurrence. Why there is a delay between two earthquakes is unknown. Clearly the waves from one earthquake carry the largest perturbation to other nearby areas, but these waves do not necessarily cause an immediate release of energy on nearby faults. The Superstition Hills Fault earthquake was certainly related to the Elmore Ranch earthquake as was the Christchurch earthquake to the Darfield. The risk associated with delayed ruptures is serious for any region that has multiple faults, such as almost all of Southern California.
Exemplary Figure Figure 5: Cumulative seismic moment plot for various Dc (m) on the SHF. For Dc greater than 0.061 m, the SHF is not triggered by waves from the point source approximation of the Elmore Ranch earthquake.