The evolution of the seismic-aseismic transition during the earthquake cycle: Constraints from the time-dependent depth distribution of aftershocks
Abstract
Using the example of the 1992 M 7.3 Landers earthquake, we show that in the aftermath of a large earthquake the depth extent of aftershocks shows an immediate deepening from pre-earthquake levels, followed by a time-dependent postseismic shallowing. We use these seismic data to constrain the change in the depth of the seismic-aseismic transition with time throughout the earthquake cycle. Most studies of the seismic-aseismic transition have focussed on the effects of temperature and/or lithology on the transition either from brittle faulting to viscous flow or from unstable to stable sliding. A strain-rate dependent transient deepening of the brittle-ductile transition following a major earthquake is predicted by geological and laboratory observations. By analyzing the time-dependent depth distributions of aftershocks, we identify and quantify the temporal evolution of this transition. In the example of the Landers earthquake, its depth changes by as much as 3 km over the course of 4 years.
- Publication:
-
Geophysical Research Letters
- Pub Date:
- December 2004
- DOI:
- 10.1029/2004GL021379
- Bibcode:
- 2004GeoRL..3123610R
- Keywords:
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- Seismology: Seismicity and seismotectonics;
- Tectonophysics: Dynamics;
- seismotectonics;
- Tectonophysics: Rheology-crust and lithosphere;
- Tectonophysics: Stresses-crust and lithosphere