Crustal thickness at the Tuxtla Volcanic Field (Veracruz, Mexico) from receiver functions

Abstract

The Tuxtla Volcanic Field (TVF) is a structure of basaltic rocks on the western margin of the Gulf of Mexico in the Mexican State of Veracruz. Located some 150 km from the easternmost tip of the Mexican Volcanic Belt, its tectonic relationship is still unclear. The volcanism, mostly alkaline, is younger than 7 Ma and has given origin to hundreds of cinder and scoria cones, maars and four large composite volcanoes, one of which, San Martín Tuxtla, erupted explosively in 1793. Due to its volcanological importance, it has been the subject of several geological studies, none of which focused on its crustal structure. Moreover, because the seismicity level in the area is relatively low, no broadband seismometers of Mexico's National Seismological Service are currently installed in the area. In this paper we present the results of the analyses of 24 teleseismic events occurring between 2004 and 2008 recorded in two broadband stations deployed around San Martín volcano. The aim of this study was to determine the depth to the Moho, any major intracrustal interface in the area, and a velocity model by means of receiver function analysis. The results show that the crustal thickness in the area varies between roughly 28 and 34 km. The receiver functions at one station suggest a second interface at a depth between 10 and 14 km. This interface is probably the contact between an upper sedimentary layer and the transitional crust found elsewhere in the margins of the Gulf of Mexico. The determination of the crustal thickness in the TVF is of importance to characterize the area and as a framework to pursue further studies of this volcanic field.