Slip rates and spatially variable creep on faults of the northern San Andreas system inferred through Bayesian inversion of Global Positioning System data
Abstract
Fault creep, depending on its rate and spatial extent, is thought to reduce earthquake hazard by releasing tectonic strain aseismically. We use Bayesian inversion and a newly expanded GPS data set to infer the deep slip rates below assigned locking depths on the San Andreas, Maacama, and Bartlett Springs Faults of Northern California and, for the latter two, the spatially variable interseismic creep rate above the locking depth. We estimate deep slip rates of 21.5 ± 0.5, 13.1 ± 0.8, and 7.5 ± 0.7 mm/yr below 16 km, 9 km, and 13 km on the San Andreas, Maacama, and Bartlett Springs Faults, respectively. We infer that on average the Bartlett Springs fault creeps from the Earth's surface to 13 km depth, and below 5 km the creep rate approaches the deep slip rate. This implies that microseismicity may extend below the locking depth; however, we cannot rule out the presence of locked patches in the seismogenic zone that could generate moderate earthquakes. Our estimated Maacama creep rate, while comparable to the inferred deep slip rate at the Earth's surface, decreases with depth, implying a slip deficit exists. The Maacama deep slip rate estimate, 13.1 mm/yr, exceeds long-term geologic slip rate estimates, perhaps due to distributed off-fault strain or the presence of multiple active fault strands. While our creep rate estimates are relatively insensitive to choice of model locking depth, insufficient independent information regarding locking depths is a source of epistemic uncertainty that impacts deep slip rate estimates.
Additional Information
© 2014 American Geophysical Union. Received 18 JAN 2014; Accepted 16 JUN 2014; Accepted article online 24 JUN 2014; Published online 21 JUL 2014. The authors wish to thank Roland Bürgmann, Yariv Hamiel, Ruth Harris, and Robert Simpson for careful reviews as well as William Ellsworth, Jeanne Hardebeck, James Lienkaemper, and William Page for useful discussions. This work was funded by Pacific Gas and Electric Company and the Earthquake Hazards Program of the USGS. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Attached Files
Published - jgrb50738.pdf
Supplemental Material - 2014JB010966_AuxREADME_final.docx
Supplemental Material - 2014JB010966_text01_final.docx
Supplemental Material - fs01.pdf
Supplemental Material - fs02a.pdf
Supplemental Material - fs02b.pdf
Supplemental Material - fs02c.pdf
Supplemental Material - fs02d.pdf
Supplemental Material - fs03a.pdf
Supplemental Material - fs03b.pdf
Supplemental Material - ts01.txt
Supplemental Material - ts02.pdf
Supplemental Material - ts03.pdf
Supplemental Material - ts04.pdf
Supplemental Material - ts05.pdf
Supplemental Material - ts06.txt
Supplemental Material - ts07.txt
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Additional details
- Eprint ID
- 49570
- Resolver ID
- CaltechAUTHORS:20140911-075334731
- Pacific Gas and Electric Company
- USGS Earthquake Hazards Program
- Created
-
2014-09-11Created from EPrint's datestamp field
- Updated
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2021-11-10Created from EPrint's last_modified field