Estimates of aseismic slip associated with small earthquakes near San Juan Bautista, CA
- Creators
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Hawthorne, J. C.
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Simons, M.
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Ampuero, J.-P.
Abstract
Postseismic slip observed after large (M > 6) earthquakes typically has an equivalent moment of a few tens of percent of the coseismic moment. Some observations of the recurrence intervals of repeating earthquakes suggest that postseismic slip following small (M ≾ 4) earthquakes could be much larger—up to 10 or 100 times the coseismic moment. We use borehole strain data from U.S. Geological Survey strainmeter SJT to analyze deformation in the days before and after 1000 1.9 < M < 5 earthquakes near San Juan Bautista, CA. We find that on average, postseismic strain is roughly equal in magnitude to coseismic strain for the magnitude range considered, suggesting that postseismic moment following these small earthquakes is roughly equal to coseismic moment. This postseismic to coseismic moment ratio is larger than typically observed in earthquakes that rupture through the seismogenic zone but is much smaller than was hypothesized from modeling repeating earthquakes. Our results are consistent with a simple, self-similar model of earthquakes.
Additional Information
© 2016 American Geophysical Union. Received 25 APR 2016; Accepted 8 OCT 2016; Accepted article online 12 OCT 2016; Published online 9 NOV 2016. Strain and creep data are provided by the United States Geological Survey and are available at http://earthquake.usgs.gov/monitoring/deformation/data/download/table.php. The NCSN earthquake catalog is available at http://www.ncedc.org/ncedc/catalog-search.html, through the Northern California Earthquake Data Center and the Berkeley Seismological Laboratory, doi 10.7932/NCEDC. Earthquake relocations were taken from Waldhauser [2009], also available through the NCEDC. The plotted fault traces are taken from the Quaternary fault and fold database for the United States, provided by the USGS and the California Geological Survey, and accessed from the USGS website http://earthquake.usgs.gov/hazards/qfaults/. Modeled atmospheric values are from the ECMWF model, available at http://apps.ecmwf.int/datasets/ [Dee et al., 2011]. Local atmospheric pressure data are from the Plate Boundary Observatory station B058, operated by UNAVCO with support from NSF, and available at http://www.unavco.org/data/strain-seismic/bsm-data/bsm-data.html. This work was supported by a Caltech Division of Geological and Planetary Sciences Texaco postdoctoral fellowship to J.C.H. We thank Nadia Lapusta for interesting discussions. We are grateful to the Associate Editor, Andy Barbour, and an anonymous reviewer for comments that improved the paper.Attached Files
Published - Hawthorne_et_al-2016-Journal_of_Geophysical_Research__Solid_Earth.pdf
Supplemental Material - jgrb51825-sup-0001-supinfo.pdf
Supplemental Material - jgrb51825-sup-0002-supinfo.txt
Supplemental Material - jgrb51825-sup-0003-supinfo.txt
Supplemental Material - jgrb51825-sup-0004-supinfo.txt
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Additional details
- Eprint ID
- 73960
- Resolver ID
- CaltechAUTHORS:20170201-153456109
- Caltech Division of Geological and Planetary Sciences
- Created
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2017-02-02Created from EPrint's datestamp field
- Updated
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2021-11-11Created from EPrint's last_modified field
- Caltech groups
- Seismological Laboratory, Division of Geological and Planetary Sciences (GPS)