Modulation of crustal tectonics by strong seismic waves
Abstract
Dynamic stresses from strong seismic waves may modulate tectonics at seismogenic depths. This process is analogous to the behavior of rupture tips on major strike-slip faults, including the San Andreas. Transient stresses at the rupture tip bring the fault into frictional failure with the laboratory coefficient of friction and generate extreme seismic waves with particle velocities of 10-30 m/s and 100-300 MPa dynamic stress at 10 km depth. The initial slip weakens the fault allowing it to slip a much lower stress. The off-fault process is conceptually simple. Frictional rock failure preferentially occurs when strong dynamic stresses align with ambient tectonic stresses. However, it is likely that the extreme rupture-tip stresses typically occur only within 10-100 m of the main fault. Widespread extreme dynamic stresses would produce observable effects within the seismogenic zone. (1) The ambient rock at 10 km depth is a fragile geological feature. Frequent failure from extreme dynamic stresses would reduce its shear wave velocity to that of damage zones around major faults. This effect would be visible along exhumed fault zones. (2) Tectonic stress is a fragile geological feature. Multiple episodes of rock failure from extreme seismic waves would relax of the ambient tectonic stress and accommodate of the long-term tectonic stress. Long-term off-fault tectonic strain would tend to occur during major San Andreas events rather than during independent events, including Coalinga, Paso Robles, and Northridge. Off-fault earthquake ruptures would tend not to propagate into regions where the tectonic stress is already relaxed
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.T13A2664S
- Keywords:
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- 8118 Dynamics and mechanics of faulting;
- TECTONOPHYSICSDE: 8120 Dynamics of lithosphere and mantle: general;
- TECTONOPHYSICSDE: 8159 Rheology: crust and lithosphere;
- TECTONOPHYSICSDE: 8163 Rheology and friction of fault zones;
- TECTONOPHYSICS