Back to Search
Start Over
Quasi-static slip patch growth to 20 m on a geological fault inferred from acoustic emissions in a South African gold mine
- Source :
- Journal of Geophysical Research: Solid Earth. 120:1692-1707
- Publication Year :
- 2015
- Publisher :
- American Geophysical Union (AGU), 2015.
-
Abstract
- Three months of acoustic emission (AE) monitoring in a South African gold mine down to Mw −5 revealed a newly emergent planar cluster of 7557 events −3.9 ≤ Mw ≤ −1.8 (typical rupture radius of 6–70 cm) that expanded with time to reach a size of 20 m on a preexisting geological fault near an active mining front 1 km beneath the ground. It had a sharply defined, planar configuration, with hypocenters aggregated within a thickness of only several decimeters. We infer that the zone defines an aseismic slip patch on the fault, wherein the individual AEs represent failures of very small asperities being loaded by the aseismic slip. Additional support for the interpretation was obtained by analyzing composite focal mechanisms and repeating events. The patch expansion over 2 months was likely quasistatic because all individual AEs ruptured much smaller areas than the cluster size at the corresponding time. The b values dropped gradually from 2.6 to 1.4, consistent with a significant increase in shear stress expected of the mining style. Another cluster with similar characteristics emerged later on a neighboring part of the same fault and grew to a 10 m extent in the last weeks of the study period. The quasi-static expansion of inferred localized slow-slip patches to sizes of 10–20 m suggests that the critical crack length on natural faults can be at least as large, much exceeding the decimeter range derived from laboratory stick-slip experiments on saw-cut rocks.
- Subjects :
- geography
geography.geographical_feature_category
Slip (materials science)
Fault (geology)
Geophysics
Planar
Acoustic emission
Space and Planetary Science
Geochemistry and Petrology
Earth and Planetary Sciences (miscellaneous)
Shear stress
Cluster size
Aseismic slip
Seismology
Geology
Quasistatic process
Subjects
Details
- ISSN :
- 21699313
- Volume :
- 120
- Database :
- OpenAIRE
- Journal :
- Journal of Geophysical Research: Solid Earth
- Accession number :
- edsair.doi...........a764eb4c89f90e6053d549cb48ffdd0d