SCEC Award Number 22108 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Investigating the effects of fault damage zones on rupture and ground motions in California
Investigator(s)
Name Organization
Domniki Asimaki California Institute of Technology Jean-Paul Ampuero California Institute of Technology
Other Participants Elif Oral, Postdoctoral Scholar, Caltech
SCEC Priorities 3d, 4c, 1d SCEC Groups FARM, GM, Seismology
Report Due Date 03/15/2023 Date Report Submitted 03/12/2024
Project Abstract
 Observations of the 2019 magnitude 7.1 Ridgecrest, California earthquake reveal a relatively low rupture speed (about $2$~km/s) and a high spatial variability of near-fault ground motions.
The medium surrounding the fault includes sedimentary rocks and a low-velocity fault damage zone. These two ingredients are known to produce source and site effects that enhance ground motions, but can also have the competing effect of slowing down rupture. Since their significance on this earthquake are unknown, the main goal of this project is to elucidate the source and site effects of sedimentary rocks and damage zones on the 2019 Ridgecrest earthquake by 3D dynamic rupture and ground motion modeling. We find that, during the 2019 Ridgecrest earthquake, the near-fault medium is likely to have increased the seismic hazard by amplifying fault slip and ground motion, in addition to wave amplification by site effects.
Such hazard increase is mainly caused by the presence of sedimentary rocks around the fault, and slightly enhanced by the presence of damage zones in the southern side of the fault.
While we report limited damage zone effects for the Ridgecrest earthquake, the variability of damage zone properties in the region allows for larger fault slips in future events, and thus warrants consideration in fault displacement hazard assessment. We also verified that the presence of sedimentary rocks and damage does not slow down the rupture considerably, therefore its overall effect is to enhance ground motion.
Intellectual Merit The intellectual merit lies on studying the competing role of sedimentary structure and damage zone on the ground motion amplification and rupture speed, using a very well documented event in California.
Broader Impacts The broader impacts lie in using results to further our understanding of near-field ground motion characteristics and seismic hazard; near field ground motion simulations are especially critical because recordings of such damaging events in close proximity to the fault are scarce and likely to govern the risk of infrastructure systems in future large magnitude events.
Exemplary Figure Figure 2