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Dependency of Supershear Transition and Ground Motion on the Autocorrelation of Initial Stress

Jan Schmedes, Ralph J. Archuleta, & Daniel Lavallee

Published 2010, SCEC Contribution #1390

We analyzed 315 dynamic strike slip rupture models computed up to 5.0 Hz to get a quantitative understanding of the correlation and amplitude distributions of parameters describing the earthquake source, such as slip, and rupture velocity. To account for the epistemic uncertainty of the problem we construct a database of dynamic ruptures computed by ourselves and other authors. This database contains ruptures computed using different models of initial stress, peak stress, and critical slip weakening distance. Using the set of computed ruptures, we are able to construct probability density functions (PDF’s) for the amplitude distributions of the source parameters and for the correlation between the source parameters themselves. We try to extract parameter pairs that show a small variability in the spatial correlation given the large epistemic uncertainty in the input. We only analyze the areas on the fault with subshear propagation speed. The principal findings of this study are: (i) final slip amplitude does not show correlation with the local rupture velocity; (ii) final slip amplitude correlates well with rise time, (iii) rupture velocity correlates well with peak slip rate and the duration of the impulsive part of the sliprate function; (iv) the PDF of rupture velocity, rise time and peak sliprate depend on the distance from the nucleation zone; (v) fracture energy is not the single controlling factor for the rupture velocity; the slope of the linear slip-weakening curve has a significant effect on the rupture velocity. (vi) The crack length (length that is slipping at a given time) decreases with the distance from the nucleation zone.

Schmedes, J., Archuleta, R. J., & Lavallee, D. (2010). Dependency of Supershear Transition and Ground Motion on the Autocorrelation of Initial Stress. Tectonophysics, 493, 222-235. doi: 10.1016/j.tecto.2010.05.013.