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Crustal structure of Oaxaca, Mexico, from seismic refraction measurements

C.M. Valdes·Walter D. Mooney·S.K. Singh·C. Lomnitz·James H. Luetgert·C.E. Helsley·B.T.R. Lewis·M. Mena
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Abstract

Seismic refraction and gravity data have been analyzed to obtain a model of the compressional-wave velocity structure of the ocean-to-continent transition in the State of Oaxaca in southwestern Mexico. Crustal thickness on the continent at the latitude 18°N is 45 ± 4 km, based on reflected phases from the Moho discontinuity. The crust has been modeled with three layers, with velocities of 4.3 to 4.6, 5.0 to 5.7, and 6.85 to 7.0 km/sec, each with positive velocity gradient. The crust thins to 10 km at the coast near Pinotepa Nacional, where Precambrian metamorphic rocks are exposed 45 km from the mid-America trench. Offshore, the oceanic structure consists of an 8-km-thick crust with a normal crustal velocity structure (Spudich and Orcutt, 1980). The apparent dip of the subducting plate beneath western Mexico is 10°. On the oceanic side, strong reflections suggest a minimum depth of 35 km for the lithosphere-asthenosphere boundary. The asthenosphere has a seismic velocity of 7.6 km/sec, and a thin lid in which the velocity is 8.6 km/sec.

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Bulletin of the Seismological Society of AmericaArticle
90° N90° S · 180° W ← longitude → 180° E
Source-reported bounding extent: 15.114552871944115° to 19.093266636089712° latitude; -99.041748046875° to -94.361572265625° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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BibTeXRIS

C.M. Valdes, Walter D. Mooney, S.K. Singh, C. Lomnitz, James H. Luetgert, C.E. Helsley, B.T.R. Lewis, M. Mena. 1986. Crustal structure of Oaxaca, Mexico, from seismic refraction measurements. https://doi.org/10.1785/bssa0760020547

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