Fault roughness and strength heterogeneity control earthquake size and stress drop

Abstract
An earthquake's stress drop is related to the frictional breakdown during sliding and constitutes a fundamental quantity of the rupture process. High-speed laboratory friction experiments that emulate the rupture process imply stress drop values that greatly exceed those commonly reported for natural earthquakes. We hypothesize that this stress drop discrepancy is due to fault-surface roughness and strength heterogeneity: an earthquake's moment release and its recurrence probability depend not only on stress drop and rupture dimension but also on the geometric roughness of the ruptured fault and the location of failing strength asperities along it. Using large-scale numerical simulations for earthquake ruptures under varying roughness and strength conditions, we verify our hypothesis, showing that smoother faults may generate larger earthquakes than rougher faults under identical tectonic loading conditions. We further discuss the potential impact of fault roughness on earthquake recurrence probability. This finding provides important information, also for seismic hazard analysis.

Citation
Zielke O, Galis M, Mai PM (2017) Fault roughness and strength heterogeneity control earthquake size and stress drop. Geophysical Research Letters 44: 777–783. Available: http://dx.doi.org/10.1002/2016gl071700.

Acknowledgements
The research reported in this publication was supported by funding from King Abdullah University of Science and Technology (KAUST). Numerical simulations for this study were carried out on the SHAHEEN II supercomputer at KAUST. Figures in the main manuscript and the online supporting information provide all the data used in this investigation. Raw data (of on-fault slip distributions) and computer codes used in this study are available from the corresponding author upon reasonable request. No financial or other types of conflicts of interest exist for the authors regarding this manuscript. We want to thank the Editor and reviewers for their construction criticism and helpful comments that improved this study.

Publisher
American Geophysical Union (AGU)

Journal
Geophysical Research Letters

DOI
10.1002/2016gl071700

Additional Links
http://onlinelibrary.wiley.com/doi/10.1002/2016GL071700/full

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