Location of Moderate-Sized Earthquakes Recorded by the NARS–Baja Array in the Gulf of California Region Between 2002 and 2006
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We relocated the hypocentral coordinates of small to moderate-sized earthquakes reported by the National Earthquake Information Center (NEIC) between April 2002 and August 2006 in the Gulf of California region and recorded by the broadband stations of the network of autonomously recording seismographs (NARS–Baja array). The NARS–Baja array consists of 19 stations installed in the Baja California peninsula, Sonora and Sinaloa, Mexico. The events reported by the preliminary determinations of epicenters (PDE) catalog within the period of interest have moment magnitudes (M w) ranging between 1.1 and 6.7. We estimated the hypocentral location of these events using P and S wave arrivals recorded by the regional broadband stations of the NARS–Baja and the RESBAN (Red Sismológica de Banda Ancha) arrays and using a standard location procedure with the HYPOCENTER code (Lienert and Havskov in Seism Res Lett 66:26–36, 1995) as a preliminary step. To refine the location of the initial hypocenters, we used the shrinking box source-specific station term method of Lin and Shearer (J Geophys Res 110, B04304, 2005). We found that most of the seismicity is distributed in the NW–SE direction along the axis of the Gulf of California, following a linear trend that, from north to south, steps southward near the main basins (Wagner, Delfin, Guaymas, Carmen, Farallon, Pescadero and Alarcon) and spreading centers. We compared the epicentral locations reported in the PDE with the locations obtained using regional arrival times, and we found that earthquakes with magnitudes in the range 3.2–5.0 mb differ on the average by as much as 43 km. For the M w magnitude range between 5 and 6.7 the discrepancy is less, differing on the average by about 25 km. We found that the relocated epicenters correlate well with the main bathymetric features of the Gulf.
KeywordsSeismicity Gulf of California Mexico
The operation of the RESBAN array (Red Sismológica de Banda Ancha) has been possible thanks to the financial support of the Mexican National Council for Science and Technology (CONACYT) by means of the projects 48852 and COC022. The NARS–Baja array was the result of a collaboration project among Utrecht University, California Institute of Technology and CICESE. The operation and data acquisition was possible thanks to Arie van Wettum, Robert Clayton, Jeannot Trampert and Hanneke Paulssen. Part of the analysis of this paper was made while one of the authors (RRC) was a UC MEXUS-CONACYT Visiting Scholar at the University of California, San Diego, IGPP-SIO. Peter Shearer kindly provided the modified version of the COMPLOC code. The useful comments and suggestions of the editor William Lee Bandy help us to improve the manuscript. We also thank the two anonymous reviewers.
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