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Crack to pulse transition and magnitude statistics during earthquake cycles on a self-similar rough fault

Heimisson, Elías Rafn (2020) Crack to pulse transition and magnitude statistics during earthquake cycles on a self-similar rough fault. Earth and Planetary Science Letters, 537 . Art. No. 116202. ISSN 0012-821X. doi:10.1016/j.epsl.2020.116202.

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Faults in nature demonstrate fluctuations from planarity at most length scales that are relevant for earthquake dynamics. These fluctuations may influence all stages of the seismic cycle; earthquake nucleation, propagation, arrest, and inter-seismic behavior. Here I show quasi-dynamic plane-strain simulations of earthquake cycles on a self-similar and finite 10 km long rough fault with amplitude-to-wavelength ratio α = 0.01. The minimum roughness wavelength, λ_(min), and nucleation length scales are well resolved and much smaller than the fault length. Stress relaxation and fault loading is implemented using a variation of the backslip approach, which allows for efficient simulations of multiple cycles without stresses becoming unrealistically large. I explore varying λ_(min) for the same stochastically generated realization of a rough fractal fault. Decreasing λ_(min) causes the minimum and maximum earthquakes sizes to decrease. Thus the fault seismicity is characterized by smaller and more numerous earthquakes, on the other hand, increasing the λ_(min) results in fewer and larger events. However, in all cases, the inferred b-value is constant and the same as for a reference no-roughness simulation(α = 0). I identify a new mechanism for generating pulse-like ruptures. Seismic events are initially crack-like, but at a critical length scale, they continue to propagate as pulses, locking in an approximately fixed amount of slip. I investigate this transition using simple arguments and derive a characteristic pulse length, L_c = λ_(min)/(4π⁴α²) and slip distance, based on roughness drag. I hypothesize that the ratio λ_(min)/α² can be roughly estimated from kinematic rupture models. Furthermore, I suggest that when the fault size is much larger than L_c, then most space-time characteristics of slip differ between a rough fault and a corresponding planar fault.

Item Type:Article
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URLURL TypeDescription
Heimisson, Elías Rafn0000-0001-8342-7226
Additional Information:© 2020 Elsevier. Received 13 October 2019, Revised 21 February 2020, Accepted 1 March 2020, Available online 12 March 2020. I want to thank Eric M. Dunham and Valere Lambert for helpful discussions and two reviewers for their constructive remarks. I partially conducted this research while being supported by NASA Headquarters under the NASA Earth and Space Science Fellowship Program (Grant NNX16AO40H). Declaration of Competing Interest: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Group:Seismological Laboratory
Funding AgencyGrant Number
NASA Earth and Space Science FellowshipNNX16AO40H
Subject Keywords:rough faults; rate-and-state friction; earthquake cycle simulations; earthquake statistics; earthquake ruptures; pulses
Record Number:CaltechAUTHORS:20200313-142322795
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Official Citation:Elías Rafn Heimisson, Crack to pulse transition and magnitude statistics during earthquake cycles on a self-similar rough fault, Earth and Planetary Science Letters, Volume 537, 2020, 116202, ISSN 0012-821X,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:101908
Deposited By: George Porter
Deposited On:16 Mar 2020 14:16
Last Modified:16 Nov 2021 18:07

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