Crustal structure below Popocat\'epetl Volcano (Mexico) from analysis of Rayleigh waves

TL;DR

This study used Rayleigh wave analysis from a temporary seismic array to model the crust beneath Popocatépetl volcano, revealing a structure similar to surrounding regions with some lateral heterogeneities at certain depths.

Contribution

It presents a new detailed crustal model beneath Popocatépetl using Rayleigh wave dispersion analysis from regional earthquakes.

Findings

Crustal velocities are consistent with the Mexican Volcanic Belt.

No large-scale anomalies detected in the sub-arrays.

Evidence of lateral heterogeneity at 5-10 km depth from individual event analysis.

Abstract

An array of ten broadband stations was installed on the Popocat\'epetl volcano (Mexico) for five months between October 2002 and February 2003. 26 regional and teleseismic earthquakes were selected and filtered in the frequency time domain to extract the fundamental mode of the Rayleigh wave. The average dispersion curve was obtained in two steps. Firstly, phase velocities were measured in the period range [2-50] s from the phase difference between pairs of stations, using Wiener filtering. Secondly, the average dispersion curve was calculated by combining observations from all events in order to reduce diffraction effects. The inversion of the mean phase velocity yielded a crustal model for the volcano which is consistent with previous models of the Mexican Volcanic Belt. The overall crustal structure beneath Popocat\'epetl is therefore not different from the surrounding area, and the velocities in the lower crust are confirmed to be relatively low. Lateral variations of the structure were also investigated by dividing the network into four parts and by applying the same procedure to each sub-array. No well-defined anomalies appeared for the two sub-arrays for which it was possible to measure a dispersion curve. However, dispersion curves associated with individual events reveal important diffraction for 6 s to 12 s periods which could correspond to strong lateral variations at 5 to 10 km depth.