Crack models of repeating earthquakes predict observed moment-recurrence scaling

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1029/2018JB016056.

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Authors

Camilla Cattania, Paul Segall

Abstract

Small repeating earthquakes are thought to represent rupture of isolated asperities loaded by surrounding creep.
The observed scaling between recurrence interval and seismic moment, Tr ~ M^(1/6), contrasts with expectation assuming constant stress drop and no aseismic slip (Tr ~ M^(1/3)). Here we demonstrate that simple crack models of velocity-weakening asperities embedded in a velocity-strengthening fault predict the Tr ~ M^(1/6) scaling; however, the mechanism depends on asperity radius, R.
For small asperities (Ri < R < 2Ri, where Ri is the nucleation radius) numerical simulations with rate-state friction show interseismic creep penetrating inwards from the edge, with earthquakes nucleating in the center and rupturing the entire asperity. Creep penetration accounts for ~25% of the slip budget, the nucleation phase takes up a larger fraction of slip. Stress drop increases with increasing R; the lack of self-similarity due to the finite nucleation dimension.
For 2 Ri < R < 4.3 Ri simulations exhibit simple cycles with ruptures nucleating from the edge. Asperities with R > 4.3Ri exhibit complex cycles of partial and full ruptures. Here Tr is explained by an energy criterion: full rupture requires that the energy release rate everywhere on the asperity at least equals the fracture energy, leading to the scaling Tr ~ M^(1/6). Remarkably, in spite of the variability in behavior with source dimension, the scaling of Tr with stress drop \Delta\tau, nucleation length and creep rate Vpl is the same across all regimes: Tr ~ (Ri)^(1/2)\Delta\tau^(5/6)M^(1/6)/Vpl. This supports the use of repeating earthquakes as creepmeters, and provides a physical interpretation for the scaling observed in nature.

DOI

https://doi.org/10.31223/osf.io/2ds5w

Subjects

Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

Keywords

Earthquake periodicity, Repeating earthquakes

Dates

Published: 2018-05-24 17:42

Last Updated: 2018-11-29 03:53

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License

CC BY Attribution 4.0 International

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