Fault roughness and strength heterogeneity control earthquake size and stress drop

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 n...

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Bibliographic Details
Published in:Geophysical research letters 2017-01, Vol.44 (2), p.777-783
Main Authors: Zielke, O., Galis, M., Mai, P. M.
Format: Article
Language:English
Subjects:
Asperity
Breakdown
Computer simulation
earthquake recurrence
earthquake size
Earthquakes
Estimates
Fault lines
fault strength
Faults
Friction
Geological faults
Geological hazards
Hazard assessment
Heterogeneity
High speed
Information dissemination
Laboratories
Numerical simulations
Plate tectonics
Probability theory
Roughness
Rupture
Rupturing
Seismic activity
Seismic analysis
Seismic hazard
Seismology
Sliding
Slumping
Strength
stress drop
Stresses
Surface roughness
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Summary: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. Key Points The observed discrepancy between laboratory‐ and field‐based stress drop estimates can be linked to fault roughness and strength asperities Field‐based estimates are biased low, not considering fault roughness. Lab‐based estimates are biased high, representing “only” asperities Smooth faults require lower stress drops than rough ones to generate the same‐size earthquake, suggesting that the prior are, respectively, weaker
ISSN:0094-8276
1944-8007
DOI:10.1002/2016GL071700