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A Crustal Velocity Model for the Peninsular Ranges of Baja California and Southwestern Laguna Salada, Mexico

Ramírez Ramos, Erik Esteban and Vidal-Villegas, José Antonio and Ramírez-Hernández, Jorge and González-Fernández, Antonio and Stock, Joann Miriam (2019) A Crustal Velocity Model for the Peninsular Ranges of Baja California and Southwestern Laguna Salada, Mexico. Seismological Research Letters, 90 (3). pp. 1219-1229. ISSN 0895-0695. http://resolver.caltech.edu/CaltechAUTHORS:20190313-105427114

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Abstract

To see any change in seismic velocities that may be associated with an abrupt change in the regional geology (granitic rock in contact with sediments), we conducted a refraction seismic study in the Peninsular Ranges of Baja California, which is in the Mexico–southwestern Laguna Salada (LS) region. We installed 30 three‐component portable seismic stations, supplemented with two permanent six‐component stations of the Northwest Mexico Seismic Network (RESNOM). The stations, spaced ∼6  km along a refraction profile, recorded two blasts; these were the direct shot located to the south of the city of Ensenada and the reverse shot in the southwestern LS (southwest–northeast direction). Record sections show seismograms with impulsive P arrivals at nearby stations. Rays from the two blasts were modeled (using asymptotic ray theory) to obtain a P‐wave velocity model from 0 to ∼15  km depth along the refraction profile. Our modeling results are as follows: in the southwestern part of the profile (0–25 km distance), a low‐velocity zone of ∼2  km/s exists between the depths of 0 and 3.5 km; in Sierra Juárez, the mean P‐wave velocity is ∼5.6  km/s between the depths of 0 and 5 km; and in southwestern LS, a low‐velocity layer of ∼2.5  km/s exists between the depths of 0 and ∼3  km. We also modeled a layer of ∼6.5  km/s between 4 and 12 km in the Ensenada–Ojos Negros region, and between the depths of 4 and 8 km below the southwestern LS. From a profile distance of 0 to 50 km, a velocity zone of ∼6.7  km/s appears between the depths of 12 and 15 km.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1785/0220180248DOIArticle
ORCID:
AuthorORCID
Stock, Joann Miriam0000-0003-4816-7865
Additional Information:© 2019 Seismological Society of America. Published Online 13 March 2019. Data and Resources: The map was made using the Generic Mapping Tools v.5.3.1, available at http://gmt.soest.hawaii.edu/ (last accessed August 2018). Some plots were made using the RAYINVR software available at http://terra.rice.edu/department/faculty/zelt/rayinvr.html (last accessed August 2018). Data from the Northwest Mexico Seismic Network (RESNOM) have been available, since 10 September 2014, from the Incorporated Research Institutions for Seismology Data Management Center (IRIS‐DMC) at http://ds.iris.edu/mda/BC (last accessed November 2018). The data used in this study are available upon request to María Alejandra Nuñez‐Leal (anunez@cicese.mx). MATLAB is available at https://www.mathworks.com/products/matlab.html (last accessed February 2019). The first author worked with the support of the National Council of Science and Technology of Mexico (CONACYT) under the Scholarship Number 254218. The CONACYT provided financial support for this project (CB‐2009‐133019 SEP‐CONACYT). Financial support and facilities were also provided by The Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), via the Earth Sciences Division and the Department of Seismology; Autonomous University of Baja California, Mexico (UABC), and its Engineering Institute, and by CICESE by way of the Earth Science Division and the Department of Seismology. The publishing charges were funded by the Programa para el Desarrollo Profesional Docente (PRODEP) 2019 program at the Universidad Autónoma de Baja California, Instituto de Ingeniería. José Acosta Chang provided the temporary short‐period seismic stations for the project; Gustavo Arellano and Euclides Ruiz provided technical support and helped during the installation of the temporary stations. For the installation of instrumentation along the profiles, the authors acknowledge Rogelio Arce, Ignacio Méndez, Oscar Gálvez, Luis Orozco, Rogelio Reyes, German Martínez, Miguel Oliver, Leandro John, and Martín Pacheco, from the Earth Sciences Division of CICESE; Frida Cital, Agustín Oropeza, Erick Jonathan Ramírez, and Iván Ramírez, from the Engineering Institute of the UABC; and Jovanny Morán, from the Technical Institute of Ensenada (ITE), Baja California, Mexico. Sergio Arregui provided the main script used for generating maps in Generic Mapping Tools, and he also wrote the programs to download seismic time series from the Northwest Mexico Seismic Network (RESNOM) database. Rafael Barajas‐Angulo provided off‐road vehicles for the installation of the temporary stations in the Mexicali Valley (MV) region. Victor Dukes allowed us to perform the Laguna Salada (LS)‐blast on his property. The authors acknowledge the explosives company (Rivada), especially Glenda Vazquez and Engineer Dagguer, for their support and help during the blast in LS. The Ministry of Environmental and Natural Resources (SEMARNAT), the Mexican Secretariat of National Defense (SEDENA), the Government of the State of Baja California, and the Municipality of Mexicali, Baja California, granted the permits required to perform the blast in LS, Baja California.
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
Consejo Nacional de Ciencia y Tecnología (CONACYT)254218
Consejo Nacional de Ciencia y Tecnología (CONACYT)CB-2009-133019 SEP-CONACYT
Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE)UNSPECIFIED
Universidad Autónoma de Baja CaliforniaUNSPECIFIED
Record Number:CaltechAUTHORS:20190313-105427114
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20190313-105427114
Official Citation:Erik Esteban Ramírez Ramos, José Antonio Vidal‐Villegas, Jorge Ramírez‐Hernández, Antonio González‐Fernández, Joann Miriam Stock; A Crustal Velocity Model for the Peninsular Ranges of Baja California and Southwestern Laguna Salada, Mexico. Seismological Research Letters ; 90 (3): 1219–1229. doi: https://doi.org/10.1785/0220180248
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:93770
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:13 Mar 2019 18:08
Last Modified:24 Apr 2019 16:55

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