Effect of Dynamic Stress Overshoot on the Prediction of Earthquake Slip in Dynamic Rupture Simulations
Abstract
The 2011 Off the Pacific Coast of Tohoku earthquake (Tohoku Earthquake, Mw 9.0) highlighted complex rupture features, such as depth-dependent seismic radiation. Also, this earthquake generated large slip, on the order of 50 m, in the shallow part of the fault. The dynamic mechanisms to generate such large shallow slip have been investigated intensely since the Tohoku earthquake using dynamic rupture simulations. In an elastic medium, the final slip distribution is linearly related to the distribution of static stress drop. In dynamic rupture simulations, stress drop is generally comparable to the nominal stress drop, defined as the difference between the initial shear stress (before the earthquake) and an a priori estimate of the final stress given by the initial normal stress times the dynamic friction coefficient. However, this parameter provides only an approximation; in particular, it ignores effects such as stress overshoot and changes of normal stress, which may play an important role in generating large slip in ruptures that reach the surface, such as the Tohoku earthquake. Thus, further analysis of the stress drop is required to understand the generation of large shallow slip in past earthquakes and to predict slip for future earthquakes.
In this study, we investigate the role of dynamic overshoot in the generation of large shallow slip by conducting dynamic rupture simulations. We assumed a linear slip-weakening friction. The overshoot contribution to stress drop is the difference between the dynamic strength and the final stress. We also evaluate the contribution of normal stress changes, quantified as the dynamic friction coefficient times the difference between initial and final normal stress. The preliminary results show that the difference between slip on the shallow part of the fault with and without overshoot is about 20%. We carry further parametric studies by changing the stress drop distribution, stress drop values, and faulting mechanism to understand the role of dynamic overshooting and normal stress changes and to formulate their effects on the prediction of slip for the future earthquakes.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMS036.0003T
- Keywords:
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- 7209 Earthquake dynamics;
- SEISMOLOGY;
- 7215 Earthquake source observations;
- SEISMOLOGY;
- 7230 Seismicity and tectonics;
- SEISMOLOGY;
- 8118 Dynamics and mechanics of faulting;
- TECTONOPHYSICS