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Near-Field Corner Frequency Analysis of Data-Integrated Large-Scale Dynamic Rupture Simulations of the 2019 Ridgecrest and the 1992 Landers Earthquakes

The rise of Distributed Acoustic Sensing and high-rate GNSS networks highlight the potential of dense ground motion observations in the near-field of large earthquakes. Physics-based spontaneous dynamic rupture simulations can provide high-resolution synthetic waveforms accounting for non-linear source, path and site complexity. We present spectral analysis of >100,000 synthetic near-field strong motion waveforms (up to 2 Hz). The waveforms are generated in observationally constrained geometrically complex 3‐D dynamic rupture simulations of the 2019 Ridgecrest sequence and the 1992 Landers earthquake (Taufiqurrahman et al., 2020; Wollherr et al., 2019), which incorporate 3-D fault geometry, high resolution topography, plastic off-fault deformation, and 3-D velocity models. We find that the spectral corner frequency may serve as a scalar proxy, which, when available with high-spatial resolution in the near-field, contains information about on-fault slip distribution, rupture directivity, fault segmentation, seismic moment, and path effects.

We generate high resolution maps of corner frequencies (f_c) determined by minimizing the misfit between the displacement spectra and the Brune model. For the analyzed dominantly strike-slip events f_c of the vertical component reveals rays of elevated corner frequencies radiating from each slipping fault in rupture forward direction. These rays indicate high accumulated slip and trace the curvature of the segmented fault systems as well as path effects such as wavefield deflections at strong velocity contrasts. A shadow zone in backwards direction of the M_w 6.4 Searles Valley foreshock indicates a unilateral rupture, whereas the ray structure of the M_w 7.1 event agrees with its bilateral rupture. Our findings highlight the future potential of spectral analysis of spatially dense (low frequency) ground motion observations for inferring earthquake kinematics and understanding earthquake physics directly from near-field data; while synthetic studies are crucial to identify "what to look for" in the vast amount of data generated.

Presenting Author: Nico Schliwa

Student Presenter: Yes

Day: 4/21/2021

Time: 2:00 PM - 3:15 PM Pacific

Additional Authors