Poster #167, Fault and Rupture Mechanics (FARM)

Exploring the effects of a sedimentary basin on the earthquake cycle using a non-stiff finite difference method for elastodynamics

Tobias Harvey, Brittany A. Erickson, & Jeremy E. Kozdon
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Poster Presentation

2021 SCEC Annual Meeting, Poster #167, SCEC Contribution #11587 VIEW PDF
Geodetic observations of long term slip on faults cutting through sedimentary basins often do not match geologic estimates. These discrepancies might be partially resolved by the heterogeneous structure of sedimentary basins, which, in addition to spatial variations in fault friction, affects the pattern of coseismic slip and interseismic creep. One hypothesis is that the drop in shear modulus of sedimentary basins inhibits surface breaking ruptures. Previously this hypothesis was tested with a series of quasi-dynamic cycle simulations of sedimentary basins with anti-plane strike-slip faults governed by a rate-state friction law which generated a periodic rupture cycle with both buried and s...urface breaking ruptures.

In quasi-dynamic modeling, inertial effects are approximated with radiation damping and it has been shown that dynamic effects can result in rupture penetration into fault regions that are not favored to slip (either due to frictional properties or the state of stress). Thus, in this work, we revisit the previous basin simulations using a newly developed method that uses a quasi-static description in the interseismic phase and the fully dynamic model during coseismic slip.

To do this we have developed a high-order finite difference scheme that is provably stable (robust) in both phases of the cycle. In the interseismic phase, large linear systems of equations must be solved to allow for large time steps. Previously, in the coseismic phase, enforcing a rate-state friction law resulted in a stiff system of equations that could be solved with a second-order semi-implicit method. We use a newly developed, non-stiff method that is compatible with the interseismic method and allows for the use of a generic explicit time-stepping method. We suspect that with the addition of dynamic effects surface rupture will occur with higher frequency.