SCEC Award Number 18166 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Simulation of earthquake cycles on faults with heterogeneous strength and rate-state friction
Investigator(s)
Name Organization
Paul Segall Stanford University Camilla Cattania Stanford University
Other Participants
SCEC Priorities 1d, 5e, 3f SCEC Groups FARM, SDOT, EFP
Report Due Date 03/15/2019 Date Report Submitted 11/11/2020
Project Abstract
 The aim of this project is to characterize seismicity on geometrically heterogeneous (fractal) faults with
pseudo-dynamic simulations of earthquake cycles. We considered a 2-D, plane strain fault loaded at an
approximately constant shear stressing rate, and found that seismicity concentrates in the final phase
of the cycle. We therefore focused on understanding foreshock sequences, and specifically the interplay
of aseismic slip and seismic events leading up to the mainshock (system-size rupture).
Intellectual Merit This work showed that on rough faults foreshocks are a consequence of both aseismic creep and static stress triggering between foreshocks. We develop a simplified model that explains the 1/t rate of foreshocks in stacked catalogs, where t is time to mainshock.
Broader Impacts This project supporting training of a young scientist who is now on the faculty of MIT.
Exemplary Figure Figure 3. Creep acceleration and seismicity leading up to the mainshock. Top: slip velocity on the
fault vs. time to the end of the mainshock, with red bars marking the rupture length and triangles
marking the nucleation point (mid-point of the region where v > Vdyn during the first earthquake time
step). Note the sudden acceleration in nearby creeping patches and the widening of the fast slipping
region with each successive seismic burst. Bottom: subset of the top panel, with events numbered by
occurrence time. Small black dots indicate the location of maximum slip velocity at each time step,
showing accelerated creep at the edges of each burst, where the subsequent ones initiate. Grey panels
show close ups of a few clustered foreshocks.
Credit: Camilla Cattania