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Seismicity in a model governed by competing frictional weakening and healing mechanisms

Hillers, G. and Carlson, J. M. and Archuleta, R. J. (2009) Seismicity in a model governed by competing frictional weakening and healing mechanisms. Geophysical Journal International, 178 (3). pp. 1363-1383. ISSN 0956-540X.

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Observations from laboratory, field and numerical work spanning a wide range of space and time scales suggest a strain dependent progressive evolution of material properties that control the stability of earthquake faults. The associated weakening mechanisms are counterbalanced by a variety of restrengthening mechanisms. The efficiency of the healing processes depends on local material properties and on rheologic, temperature, and hydraulic conditions. We investigate the relative effects of these competing non-linear feedbacks on seismogenesis in the context of evolving frictional properties, using a mechanical earthquake model that is governed by slip weakening friction. Weakening and strengthening mechanisms are parametrized by the evolution of the frictional control variable—the slip weakening rate R—using empirical relationships obtained from laboratory experiments. In our model, weakening depends on the slip of an earthquake and tends to increase R, following the behaviour of real and simulated frictional interfaces. Healing causes R to decrease and depends on the time passed since the last slip. Results from models with these competing feedbacks are compared with simulations using non-evolving friction. Compared to fixed R conditions, evolving properties result in a significantly increased variability in the system dynamics. We find that for a given set of weakening parameters the resulting seismicity patterns are sensitive to details of the restrengthening process, such as the healing rate b and a lower cutoff time, tc , up to which no significant change in the friction parameter is observed. For relatively large and small cutoff times, the statistics are typical of fixed large and small R values, respectively. However, a wide range of intermediate values leads to significant fluctuations in the internal energy levels. The frequency-size statistics of earthquake occurrence show corresponding non-stationary characteristics on time scales over which negligible fluctuations are observed in the fixed-R case. The progressive evolution implies that -— except for extreme weakening and healing rates -— faults and fault networks possibly are not well characterized by steady states on typical catalogue time scales, thus highlighting the essential role of memory and history dependence in seismogenesis. The results suggest that an extrapolation to future seismicity occurrence based on temporally limited data may be misleading due to variability in seismicity patterns associated with competing mechanisms that affect fault stability.

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Additional Information:Copyright © 2009 The Authors. Journal compilation Copyright © 2009 RAS. Accepted 2009 April 17. Received 2009 April 16; in original form 2008 July 29. Published Online: 24 July 2009. We thank A. Martin for the outstanding and timely computational assistance that underpinned much of this work. We thank M. L. Manning for a critical in-house review, and comments by Editor C. Ebinger, A. Bizzarri and an anonymous reviewer helped to improve the manuscript. G. H. was supported by the Swiss National Science Foundation, contribution number PBEZ2-111586, by the James S. McDonnell Foundation, the David and Lucile Packard Foundation, and the NSF under grant DMR-0606092. This research was supported by the Southern California Earthquake Center. SCEC is funded by NSF Cooperative Agreement EAR-0529922 and USGS Cooperative Agreement 07HQAG0008. The SCEC contribution number for this paper is 1190. The Institute for Crustal Studies contribution number for this paper is 0873. Computations were carried out on the 'Dragon' cluster of the Institute for Crustal Studies, University of California, Santa Barbara.
Funding AgencyGrant Number
Swiss National Science Foundation (SNSF)PBEZ2-111586
James S. McDonnell FoundationUNSPECIFIED
David and Lucile Packard FoundationUNSPECIFIED
Southern California Earthquake CenterUNSPECIFIED
Subject Keywords:Seismic cycle; Earthquake dynamics; Rheology and friction of fault zones
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Other Numbering System NameOther Numbering System ID
Southern California Earthquake Center1190
Issue or Number:3
Record Number:CaltechAUTHORS:20090828-231037402
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:15470
Deposited By: George Porter
Deposited On:15 Sep 2009 15:38
Last Modified:03 Oct 2019 00:58

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