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Off-fault damage and acoustic emission distributions during the evolution of structurally complex faults over series of stick-slip events

Goebel, T. H. W. and Becker, T. W. and Sammis, C. G. and Dresen, G. and Schorlemmer, D. (2014) Off-fault damage and acoustic emission distributions during the evolution of structurally complex faults over series of stick-slip events. Geophysical Journal International, 197 (3). pp. 1705-1718. ISSN 0956-540X.

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Variations in fault structure, for example, surface roughness and deformation zone width, influence the location and dynamics of large earthquakes as well as the distribution of small seismic events. In nature, changes in fault roughness and seismicity characteristics can rarely be studied simultaneously, so that little is known about their interaction and evolution. Here, we investigate the connection between fault structure and near-fault distributions of seismic events over series of stick-slip cycles in the laboratory. We conducted a set of experiments on rough faults that developed from incipient fracture surfaces. We monitored stress and seismic activity which occurred in the form of acoustic emissions (AEs). We determined AE density distributions as a function of fault normal distance based on high-accuracy hypocentre locations during subsequent interslip periods. The characteristics of these distributions were closely connected to different structural units of the faults, that is, the fault core, off-fault and background damage zone. The core deformation zone was characterized by consistently high seismic activity, whereas the off-fault damage zone displayed a power-law decay of seismic activity with increasing distance from the fault core. The exponents of the power-law-distributed off-fault activity increased with successive stick-slip events so that later interslip periods showed a more rapid spatial decay of seismic activity from the fault. The increase in exponents was strongest during the first one to three interslip periods and reached approximately constant values thereafter. The relatively rapid spatial decay of AE events during later interslip periods is likely an expression of decreasing fault zone complexity and roughness. Our results indicate a close relationship between fault structure, stress and seismic off-fault activity. A more extensive mapping of seismic off-fault activity-decay has the potential to significantly advance the understanding of fault zone properties including variations in fault roughness and stress.

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Additional Information:© 2014 The Authors. Published by Oxford University Press on behalf of The Royal Astronomical Society. Accepted 2014 February 24. Received 2014 February 19; in original form 2013 October 5. First published online: April 29, 2014. We thank Stefan Gehrmann and Matthias Kreplin for the rock sample preparation at GFZ-Potsdam, Germany. The authors wish to thank the editor, Jörg Renner, and two anonymous reviewers for suggestions that helped improve an earlier version of the manuscript. This research was supported in part by the Southern Californian Earthquake Center under contribution numbers 11017 and 13022.
Funding AgencyGrant Number
Southern Californian Earthquake Center (SCEC)11017
Southern Californian Earthquake Center (SCEC)13022
Subject Keywords:Microstructures; Seismicity and tectonics; Statistical seismology; Rheology and friction of fault zones; Dynamics and mechanics of faulting; Fractures and faults
Issue or Number:3
Record Number:CaltechAUTHORS:20140707-143336352
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46904
Deposited By: Tony Diaz
Deposited On:07 Jul 2014 21:58
Last Modified:03 Oct 2019 06:47

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