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Source Functions and Path Effects from Earthquakes in the Farallon Transform Fault Region, Gulf of California, Mexico that Occurred on October 2013

Castro, Raúl R. and Stock, Joann M. and Hauksson, Egill and Clayton, Robert W. (2017) Source Functions and Path Effects from Earthquakes in the Farallon Transform Fault Region, Gulf of California, Mexico that Occurred on October 2013. Pure and Applied Geophysics, 174 (6). pp. 2239-2256. ISSN 0033-4553.

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We determined source spectral functions, Q and site effects using regional records of body waves from the October 19, 2013 (M_w = 6.6) earthquake and eight aftershocks located 90 km east of Loreto, Baja California Sur, Mexico. We also analyzed records from a foreshock with magnitude 3.3 that occurred 47 days before the mainshock. The epicenters of this sequence are located in the south-central region of the Gulf of California (GoC) near and on the Farallon transform fault. This is one of the most active regions of the GoC, where most of the large earthquakes have strike–slip mechanisms. Based on the distribution of the aftershocks, the rupture propagated northwest with a rupture length of approximately 27 km. We calculated 3-component P- and S-wave spectra from ten events recorded by eleven stations of the Broadband Seismological Network of the GoC (RESBAN). These stations are located around the GoC and provide good azimuthal coverage (the average station gap is 39°). The spectral records were corrected for site effects, which were estimated calculating average spectral ratios between horizontal and vertical components (HVSR method). The site-corrected spectra were then inverted to determine the source functions and to estimate the attenuation quality factor Q. The values of Q resulting from the spectral inversion can be approximated by the relations Q_P =48.1±1.1f^(0.88±0.04) and Q_S =135.4±1.1f^(0.58±0.03) and are consistent with previous estimates reported by Vidales-Basurto et al. (Bull Seism Soc Am 104:2027–2042, 2014) for the south-central GoC. The stress drop estimates, obtained using the ω2 model, are below 1.7 MPa, with the highest stress drops determined for the mainshock and the aftershocks located in the ridge zone. We used the values of Q obtained to recalculate source and site effects with a different spectral inversion scheme. We found that sites with low S-wave amplification also tend to have low P-wave amplification, except for stations BAHB, GUYB and SFQB, located on igneous rocks, where the P-wave site amplification is higher.

Item Type:Article
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URLURL TypeDescription ReadCube access chapter reprint from journal chapter reprint from journal
Stock, Joann M.0000-0003-4816-7865
Hauksson, Egill0000-0002-6834-5051
Clayton, Robert W.0000-0003-3323-3508
Additional Information:© 2016 Springer International Publishing. Received: 25 January 2016; Revised: 27 June 2016; Accepted: 29 June 2016; First Online: 09 July 2016. The operation of the RESBAN network has been possible thanks to the financial support of the Mexican National Council for Science and Technology (CONACYT) (projects CB-2011-01-165401(C0C059), G33102-T and 59216). This paper was prepared while the first author (RRC) was on sabbatical year in Caltech. We thank Prof. Gurnis for the support provided. Dr. Lenin Avila-Barrientos facilitated part of the spectral records used to calculate the site functions. Antonio Mendoza Camberos pre-process the data from the RESBAN network and Arturo Perez Vertti maintains and operates the stations. We thank Dr. Edwards and the anonymous reviewer for their careful revisions, comments and suggestions which help us to improve the manuscript. We also acknowledge the Editor, Dr. Thomas H.W. Goebel.
Group:Seismological Laboratory
Funding AgencyGrant Number
Consejo Nacional de Ciencia y Tecnología (CONACYT)CB-2011-01-165401
Consejo Nacional de Ciencia y Tecnología (CONACYT)C0C059
Consejo Nacional de Ciencia y Tecnología (CONACYT)G33102-T
Consejo Nacional de Ciencia y Tecnología (CONACYT)59216
Subject Keywords:Earthquakes in the Gulf of California; source and path effects; Farallon transform fault
Issue or Number:6
Record Number:CaltechAUTHORS:20161109-071414936
Persistent URL:
Official Citation:Castro, R.R., Stock, J.M., Hauksson, E. et al. Pure Appl. Geophys. (2017) 174: 2239. doi:10.1007/s00024-016-1346-4
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:71851
Deposited By: Tony Diaz
Deposited On:09 Nov 2016 18:11
Last Modified:03 Oct 2019 16:11

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