SCEC Award Number 12228 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Dynamic Models of the Long-Term Earthquake Cycle at Parkfield
Investigator(s)
Name Organization
Sylvain Barbot California Institute of Technology
Other Participants Nadia Lapusta and Jean-Philippe Avouac (no additional support requested); a current first-year graduate student
SCEC Priorities 3f, 2d, 2e SCEC Groups FARM, SDOT, EFP
Report Due Date 03/15/2013 Date Report Submitted N/A
Project Abstract
 The objective of the project is to establish a physical model for the sequence of earthquakes in the last 150 years at Parkfield and explain the long-term variability of recurrence times of Mw 6 earthquakes. One of these moderate-size earthquakes occurred only 10 years after a previous one, and the latest 2004 earthquake occurred after a long 38 years after the 1966 event. A clue of the origin of the variability of the earthquake cycle comes from the Parkfield seismic crisis of 1993-94, which occurred at the expected due date of the latest Mw 6 earthquake, and presumably delayed it. This observation leads to the hypothesis that variability in earthquake size leads to variability of recurrence time of the largest earthquakes in a given region.

The practical goals of the project are to explore the physical factors - such as the enhanced dynamic weakening during seismic events, motion of pore fluids, interaction with nearby segments, static and/or dynamic triggering - that could cause the observed rich behavior of faulting. Could the interaction of multiple physical phenomena spontaneously generate small and large events, with the largest events exhibiting a complex pattern of recurrence time?

Such physical models of fault slip evolution would provide an indispensable tool for understanding the earthquake cycle at Parkfield and more broadly improve our capacity to mitigate seismic hazards around active faults.
Intellectual Merit The project explores the physics of earthquake faults and test hypothesis regarding sequence of earthquakes that would help us understand the physics of faulting at other locations. This work will be directly relevant to the Fault and Rupture Mechanics (FARM), the Stress and Deformation Over Time (SDOT) and the Earthquake Forecasting and Predictability (EFP) interdisciplinary focus groups, via (i) developing physics-based models of the nucleation, propagation, and arrest of dynamic earthquake rupture; (ii) contributing to the development of of a physics-based, probabilistic seismic hazard analysis at time scales down to the earthquake cycle (iii) increasing our understanding of how earthquakes might be forecast, whether or not earthquakes are predictable, and whether of not there exist a physical basis for earthquake predictability.
Broader Impacts The proposed work is directly relevant to the long term goals of SCEC4, including Section 2 (Stress-mediated fault interactions and earthquake clustering: evaluation of mechanisms), Section 3 (Evolution of fault resistance during seismic slip: scale-appropriate laws for rupture modeling), and Section 4 (Structure and evolution of fault zones and systems: relation to earthquake physics).
Exemplary Figure Figure 1. Modeled fault slip evolution. The white circles indicate microseismicity and the grey lines are contours of the cumulative slip. The green and red stars indicate the 1966 and the 2004 hypocenters, respectively. A) Nucleation phase. B) Rupture propagation C) Interseismic period. C) Seismic and aseismic slip advance over 10 earthquake cycles with a transition of hypocenter location.
Linked Publications

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