Study of the Internal Structure, Dynamic Rupture, and Post-Earthquake Healing of the Hector Mine Earthquake Rupture Zone Using Fault-Zone Trapped Waves

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EAR-0001132University of Southern CaliforniaThe M7.1 Hector Mine, California, earthquake in 1999 provides an excellent site for capture of fault-zone guided waves. 3 days after the mainshock coordinated by the USGS, we deployed a seismic array of a 60-channel GEOMETRICS recorder from PASSCAL across the surface rupture near the epicenter and recorded ~800 aftershocks in 10 days. The data show 4-6 Hz fault-zone trapped waves at stations close to the surface rupture for events occurring within the rupture zone. Afterwards, the SCEC organized a deployment of 83 PASSCAL REFTEKs at 2 sites on the rupture zones. ~2000 aftershocks were recorded in 4 weeks. We propose to do a systematic analysis and FD-FE modeling of fault-zone trapped wave data for more information about the internal structure of the rupture zone, physical nature of fault segmentation, the relationship between the fault zone structure and dynamic rupture process as well as the healing of the fault after a major earthquake. The main tasks of this proposal are: 1. To delineate the physical properties and fine structure of the fault zone in 3-D. 2. to repeat seismic surveys using explosions for monitoring the fault healing. 3. to simulate the rupture through the fault stepovers characterized by trapped waves, and assess the rupture velocity variations, extent of slip, dynamics stresses and nonlinear energy dissipation in the fault zone during the rupture for a better understanding the damage mechanism, fault friction and rheology. 4. to analyse shear-wave splitting for additional information on the stress state and fracture matrix around the rupture zone.