How Related Are Step-overs To Stopping Earthquake Rupture?
Abstract
We expand on an existing empirical dataset in order to examine structural controls on earthquake rupture propagation. The dataset is composed of mapped historical earthquake surface rupture traces in continental crust. The goal is to understand the connection between geometrical discontinuities and the ultimate extent to which a rupture will propagate. We define geometrical discontinuities as step-overs, gaps, splays, and parallel faults along the length of the rupture trace. The expanded dataset contains 62 earthquakes (35 strike-slip, 14 reverse, 13 normal). Results show that longer ruptures do not necessarily have more steps. Within the dataset, the number of earthquakes is a decreasing function of the number of steps observed along strike. The relationship also holds if the data are divided into strike-slip, normal, and reverse type subsets. These observations are consistent with dynamic modeling that associates steps with energy sinks that hinder and can stop rupture propagation. Within the dataset it is also observed that normal and reverse mechanism events have propagated across larger step sizes than have strike-slip ruptures. The difference seems to be associated with the mechanism of the earthquake. The rupture process of a dip-slip earthquake does not involve volumetric changes within steps as it does in steps along strike-slip ruptures. As such, geometric roughness and step sizes that would kinematically hinder strike-slip ruptures have less effect on dip-slip earthquakes.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.S13B..06M
- Keywords:
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- 7205 SEISMOLOGY / Continental crust;
- 7209 SEISMOLOGY / Earthquake dynamics;
- 8010 STRUCTURAL GEOLOGY / Fractures and faults;
- 8107 TECTONOPHYSICS / Continental neotectonics