The evolution of the seismic-aseismic transition during the earthquake cycle: Constraints from the time-dependent depth distribution of aftershocks

Frederique Rolandone, Roland Bürgmann, & Robert M. Nadeau

Published December 2004, SCEC Contribution #807

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.

Citation
Rolandone, F., Bürgmann, R., & Nadeau, R. M. (2004). The evolution of the seismic-aseismic transition during the earthquake cycle: Constraints from the time-dependent depth distribution of aftershocks. Geophysical Research Letters, 31, L23610. doi: 10.1029/2004GL021379.