Crustal structure of Mexico and surrounding regions from seismic ambient noise tomography

Abstract

S U M M A R YUsing continuous seismic data from newly available broadband stations in Mexico and Central America we have obtained group and phase velocity maps of fundamental mode Rayleigh wave for the region. These new maps have been calculated for periods between 8 and 60 s from cross-correlations of seismic ambient noise between 100 broadband stations, and stacked for 30 months from 2006 to 2008. The tomographic inversion of the obtained dispersion measurements has been carried out on a 1 • × 1 • grid, resulting in maps with resolution better than 250 km in the well-sampled regions of the model. For short periods (8-16 s) dispersion maps show good correlation with surface structural features. Low-velocity anomalies correlate with sedimentary basins around the Gulf of Mexico and Colorado embayment. High-velocity anomalies at short periods correlate with mountain ranges and regions of thin, extended crust such as the Gulf of California. Both the lowest and highest group velocity anomalies at these periods reach values of up to 15 per cent. For periods between 25 and 40 s, velocity anomalies are related to variations in crustal thickness and temperature. The most prominent low velocity anomaly correlates with thick crust and high mantle temperatures associated with the TransMexican Volcanic Belt and the Central American volcanic arc. The most remarkable features for longer periods (40-60 s) are the differences between high-velocity anomalies beneath the Mayan block, the Gulf of Mexico and the cratonic part of the United States and low-velocity anomalies beneath the Chortis block and northern Mexico. The long wavelength features of our model agree well with previous global and continental scale studies. However, because of the increased station density of the data set used, we are able to obtain reliable dispersion maps for shorter periods, and to image smaller scale features.

Crustal and upper mantle structure beneath the Gulf of Mexico and the Caribbean Sea from Rayleigh‐wave analysis

“…The S‐velocity map shows clearly the distribution of sedimentary basins of the study area. These sedimentary basins were plotted by Gaite, Iglesias, Villaseñor, Herraiz, and Pacheco (). The S‐velocity presents the lowest values for the basins with thicker sediments, as in the north‐west of the Gulf of Mexico.…”

“…Bassin, Laske, and Masters () determined low‐phase velocities in the Gulf of Mexico and Vdovin, Rial, Levshin, and Ritzwoller () also determined low group velocities in this region, for short periods. For the southern part of the Caribbean Sea region, the S‐velocity also shows lower values in areas with thicker sediments (Gaite et al, ). These low velocities are expected in this region, because the sediments thickness in the Caribbean oceanic plateau (Figure ) is 2 km (Burke, Fox, & Sengör, ; Mann, ).…”

Tomografía de Velocidad de Grupo de Ondas de Rayleigh para el Oriente de México y el Istmo de Tehuantepec

“…En general, las anomalías de baja velocidad muestran una correspondencia con cuencas sedimentarias, mientras que las de alta velocidad están asociadas con los principales rasgos fisiográficos tales como la Sierra Madre Oriental y la Sierra Madre del Sur (e.g., Gaite et al, 2012). Los mapas tomográficos de velocidad de grupo obtenidos presentan una buena correlación con las estructuras geológicas más prominentes de la región de estudio.…”

“…En el caso de México a escala regional, Gaite et al (2012) calcularon mapas de velocidad de grupo y de fase para ondas de Rayleigh a partir de registros de ruido ambiental de estaciones localizadas en el Caribe, Estados Unidos, Centroamérica y México. Con este propósito, los autores obtuvieron ~2500 curvas de dispersión individuales correspondientes a pares de estaciones sísmicas, y usando el método propuesto por Barmin et al (2001), determinaron mapas de velocidad de grupo y de fase para periodos entre los 8 y los 60 s. Los autores de este trabajo reportan que la resolución alcanzada fue de hasta 250 x 250 km en las regiones con mejor cobertura de trayectorias interestaciones.…”

Ambient seismic noise Rayleigh wave tomography for the Pannonian basin

“…The closer the stations are to each other, the shorter the period of surface waves are measurable and the shallower structure can be revealed. The method has been successfully applied in local (Boaga et al, 2010), regional (Sabra et al, 2005;Shapiro et al, 2005;Villaseñor et al, 2007;Gaite et al, 2012;Kim et al, 2012;Verbeke et al, 2012) and continental studies Bensen et al, 2008).…”