Modeling Strong-Motion Recordings of the 2010 Mw 8.8 Maule, Chile, Earthquake with High Stress-Drop Subevents and Background Slip

Strong-motion recordings of the M-w 8.8 Maule earthquake were modeled using a compound rupture model consisting of (1) a background slip distribution with large correlation lengths, relatively low slip velocity, and long peak rise time of slip of about 10 s and (2) high stress-drop subevents (asperities) on the deeper portion of the rupture with moment magnitudes 7.9-8.2, high slip velocity, and rise times of slip of about 2 s. In this model, the high-frequency energy is not produced in the same location as the peak coseismic slip, but is generated in the deeper part of the rupture zone. Using synthetic seismograms generated for a plane-layered velocity model, I find that the high stress-drop subevents explain the observed Fourier spectral amplitude from about 0.1 to 1.0 Hz. Broadband synthetics (0-10 Hz) were calculated by combining deterministic synthetics derived from the background slip and asperities (<= 1 Hz) with stochastic synthetics generated only at the asperities (>= 1 Hz). The broadband synthetics produced response spectral accelerations with low bias compared to the data, for periods of 0.1-10 s. A subevent stress drop of 200-350 bars for the high-frequency stochastic synthetics was found to bracket the observed spectral accelerations at frequencies greater than 1 Hz. For most of the stations, the synthetics had durations of the Arias intensity similar to the observed records.