TY - JOUR
T1 - Evolution of b-value during the seismic cycle
T2 - Insights from laboratory experiments on simulated faults
AU - Rivière, J.
AU - Lv, Z.
AU - Johnson, P. A.
AU - Marone, C.
N1 - Funding Information:
This work was supported by a Marie-Curie Fellowship to JR (Award Number 655833 ), and grants from the DOE-Geothermal program , the NSF ( 1547441 and 1520760 ), and the USGS/NEHRP (Award Numbers G16AP00028 & G16AP00027 ) to CJM. PAJ acknowledges DOE Geothermal and Institutional Support (LDRD) at Los Alamos National Laboratory .
Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2018/1/15
Y1 - 2018/1/15
N2 - 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 μm/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.
AB - 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 μm/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.
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U2 - 10.1016/j.epsl.2017.11.036
DO - 10.1016/j.epsl.2017.11.036
M3 - Article
AN - SCOPUS:85035097227
SN - 0012-821X
VL - 482
SP - 407
EP - 413
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
ER -