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Active Pacific North America Plate boundary tectonics as evidenced by seismicity in the oceanic lithosphere offshore Baja California, Mexico

Hauksson, Egill and Kanamori, Hiroo and Stock, Joann and Cormier, Marie-Helene and Legg, Mark (2014) Active Pacific North America Plate boundary tectonics as evidenced by seismicity in the oceanic lithosphere offshore Baja California, Mexico. Geophysical Journal International, 196 (3). pp. 1619-1630. ISSN 0956-540X. doi:10.1093/gji/ggt467.

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Pacific Ocean crust west of southwest North America was formed by Cenozoic seafloor spreading between the large Pacific Plate and smaller microplates. The eastern limit of this seafloor, the continent–ocean boundary, is the fossil trench along which the microplates subducted and were mostly destroyed in Miocene time. The Pacific–North America Plate boundary motion today is concentrated on continental fault systems well to the east, and this region of oceanic crust is generally thought to be within the rigid Pacific Plate. Yet, the 2012 December 14 M_w 6.3 earthquake that occurred about 275 km west of Ensenada, Baja California, Mexico, is evidence for continued tectonism in this oceanic part of the Pacific Plate. The preferred main shock centroid depth of 20 km was located close to the bottom of the seismogenic thickness of the young oceanic lithosphere. The focal mechanism, derived from both teleseismic P-wave inversion and W-phase analysis of the main shock waveforms, and the 12 aftershocks of M ∼3–4 are consistent with normal faulting on northeast striking nodal planes, which align with surface mapped extensional tectonic trends such as volcanic features in the region. Previous Global Positioning System (GPS) measurements on offshore islands in the California Continental Borderland had detected some distributed Pacific and North America relative plate motion strain that could extend into the epicentral region. The release of this lithospheric strain along existing zones of weakness is a more likely cause of this seismicity than current thermal contraction of the oceanic lithosphere or volcanism. The main shock caused weak to moderate ground shaking in the coastal zones of southern California, USA, and Baja California, Mexico, but the tsunami was negligible.

Item Type:Article
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URLURL TypeDescription
Hauksson, Egill0000-0002-6834-5051
Kanamori, Hiroo0000-0001-8219-9428
Stock, Joann0000-0003-4816-7865
Additional Information:© 2013 Authors. Published by Oxford University Press on behalf of The Royal Astronomical Society. Accepted 2013 November 15. Received 2013 November 14; in original form 2013 April 4. First published online: December 19, 2013. We thank C. Sorlien and L. Jones for helpful discussions and the personnel of the USGS/Caltech SCSN and the Southern California Earthquake Data Center (SCEDC) for data collection and distribution. The IRIS DMS data center was used to access the seismic data from GSN and FDSN stations. EH was supported by NEHRP/USGS grant G13AP00047. This research was also supported by the Southern California Earthquake Center, which is funded by NSF Cooperative Agreement EAR-0529922 and USGS Cooperative Agreement 07HQAG0008. This paper is SCEC contribution # 1745 and contribution # 10089 of Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA.
Group:Seismological Laboratory, Division of Geological and Planetary Sciences
Funding AgencyGrant Number
Southern California Earthquake Center (SCEC)UNSPECIFIED
Subject Keywords:Earthquake source observations; Seismicity and tectonics; Transform faults; Kinematics of crustal and mantle deformation; Rheology: crust and lithosphere.
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Other Numbering System NameOther Numbering System ID
Southern California Earthquake Center (SCEC)1745
Caltech Division of Geological and Planetary Sciences10089
Issue or Number:3
Record Number:CaltechAUTHORS:20140403-094603730
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Official Citation:Seismology: Egill Hauksson, Hiroo Kanamori, Joann Stock, Marie-Helene Cormier, and Mark Legg Active Pacific North America Plate boundary tectonics as evidenced by seismicity in the oceanic lithosphere offshore Baja California, Mexico Geophys. J. Int. (March, 2014) 196 (3): 1619-1630 first published online December 19, 2013 doi:10.1093/gji/ggt467
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:44628
Deposited By: Ruth Sustaita
Deposited On:03 Apr 2014 17:12
Last Modified:10 Nov 2021 16:54

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