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U.S. Geological Survey Open-File Report 2010–1333
Jointly published as California Geological Survey Special Report 221

Prepared in cooperation with the California Geological Survey; University of Oregon; University of Colorado; University of California, San Diego; and Jet Propulsion Laboratory, California Institute of Technology.

Triggered Surface Slips in Southern California Associated with the 2010 El Mayor-Cucapah, Baja California, Mexico, Earthquake

By Michael J. Rymer, Jerome A. Treiman, Katherine J. Kendrick, James J. Lienkaemper, Ray J. Weldon, Roger Bilham, Meng Wei, Eric J. Fielding, Janis L. Hernandez, Brian P. E. Olson, Pamela J. Irvine, Nichole Knepprath, Robert R. Sickler, Xiaopeng Tong, and Martin E. Siem

Thumbnail of and link to report PDF (21.7 MB)Abstract

The April 4, 2010 (Mw7.2), El Mayor-Cucapah, Baja California, Mexico, earthquake is the strongest earthquake to shake the Salton Trough area since the 1992 (Mw7.3) Landers earthquake. Similar to the Landers event, ground-surface fracturing occurred on multiple faults in the trough. However, the 2010 event triggered surface slip on more faults in the central Salton Trough than previous earthquakes, including multiple faults in the Yuha Desert area, the southwestern section of the Salton Trough. In the central Salton Trough, surface fracturing occurred along the southern San Andreas, Coyote Creek, Superstition Hills, Wienert, Kalin, and Imperial Faults and along the Brawley Fault Zone, all of which are known to have slipped in historical time, either in primary (tectonic) slip and/or in triggered slip. Surface slip in association with the El Mayor-Cucapah earthquake is at least the eighth time in the past 42 years that a local or regional earthquake has triggered slip along faults in the central Salton Trough. In the southwestern part of the Salton Trough, surface fractures (triggered slip) occurred in a broad area of the Yuha Desert. This is the first time that triggered slip has been observed in the southwestern Salton Trough.

Triggered slip in the Yuha Desert area occurred along more than two dozen faults, only some of which were recognized before the April 4, 2010, El Mayor-Cucapah earthquake. From east to northwest, slip occurred in seven general areas: (1) in the Northern Centinela Fault Zone (newly named), (2) along unnamed faults south of Pinto Wash, (3) along the Yuha Fault (newly named), (4) along both east and west branches of the Laguna Salada Fault, (5) along the Yuha Well Fault Zone (newly revised name) and related faults between it and the Yuha Fault, (6) along the Ocotillo Fault (newly named) and related faults to the north and south, and (7) along the southeasternmost section of the Elsinore Fault. Faults that slipped in the Yuha Desert area include northwest-trending right-lateral faults, northeast-trending left-lateral faults, and north-south faults, some of which had dominantly vertical offset. Triggered slip along the Ocotillo and Elsinore Faults appears to have occurred only in association with the June 14, 2010 (Mw5.7), aftershock. This aftershock also resulted in slip along other faults near the town of Ocotillo. Triggered offset on faults in the Yuha Desert area was mostly less than 20 mm, with three significant exceptions, including slip of about 50–60 mm on the Yuha Fault, 40 mm on a fault south of Pinto Wash, and about 85 mm on the Ocotillo Fault. All triggered slips in the Yuha Desert area occurred along preexisting faults, whether previously recognized or not.

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Menlo Park, California 94025
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Suggested citation:

Rymer, M.J., Treiman, J.A., Kendrick, K.J., Lienkaemper, J.J., Weldon, R.J., Bilham, R., Wei, M., Fielding, E.J., Hernandez, J.L., Olson, B.P.E., Irvine, P.J., Knepprath, N., Sickler, R.R., Tong, .X., and Siem, M.E., 2011, Triggered surface slips in southern California associated with the 2010 El Mayor-Cucapah, Baja California, Mexico, earthquake: U.S. Geological Survey Open-File Report 2010–1333 and California Geological Survey Special Report 221, 62 p., available at https://pubs.usgs.gov/of/2010/1333/.



Contents

Abstract

Introduction

Timing of Fault Slip

Methods

San Andreas Fault

Coyote Creek Fault

Superstition Hills Fault

Wienert Fault

Superstition Mountain Fault

Kalin Fault

Imperial Fault

Brawley Fault Zone

Faults in the Yuha Desert Area

June 14 Mw5.7 Aftershock

Other Faults

Timing of Triggered Slip in the Yuha Desert Area

Acknowledgments

References Cited

one Appendix


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