期刊
EARTH AND PLANETARY SCIENCE LETTERS
卷 482, 期 -, 页码 407-413出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.epsl.2017.11.036
关键词
earthquakes; friction; fault; seismic cycle; b-value; acoustic emission
资金
- Marie-Curie Fellowship [655833]
- DOE-Geothermal program
- NSF [1547441, 1520760]
- USGS/NEHRP [G16AP00028, G16AP00027]
- Marie Curie Actions (MSCA) [655833] Funding Source: Marie Curie Actions (MSCA)
- Division Of Earth Sciences
- Directorate For Geosciences [1547441, 1520760] Funding Source: National Science Foundation
We investigate the evolution of the frequency-magnitude b-value during stable and unstable frictional sliding experiments. Using a biaxial shear configuration, we record broadband acoustic emissions (AE) while shearing layers of simulated granular fault gouge under normal stresses of 2-8 MPa and shearing velocity of 11 mu m/s. AE event amplitude ranges over 3-4 orders of magnitude and we find an inverse correlation between b and shear stress. The reduction of b occurs systematically as shear stress rises prior to stick-slip failure and indicates a greater proportion of large events when faults are more highly stressed. For quasi-periodic stick-slip events, the temporal evolution of b has a characteristic saw-tooth pattern: it slowly drops as shear stress increases and quickly jumps back up at the time of failure. The rate of decrease during the inter-seismic period is independent of normal stress but the average value of b decreases systematically with normal stress. For stable sliding, b is roughly constant during shear, however it exhibits large variability. During irregular stick-slip, we see a mix of both behaviors: b decreases during the interseismic period between events and then remains constant when shear stress stabilizes, until the next event where a co-seismic increase is observed. Our results will help improve seismic hazard assessment and, ultimately, could aid earthquake prediction efforts by providing a process-based understanding of temporal changes in b-value during the seismic cycle. (C) 2017 Elsevier B.V. All rights reserved.
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