Ambient noise tomography of Popocatépetl volcano, México

Popocatépetl volcano is among Mexico’s most risky due to its proximity to populated areas. Since its reactivation in 1994, several geophysical studies have been performed to understand the eruptive history, volcanic activity, and associated hazards. Although several seismic studies were carried out using permanent and temporal seismic network records, the internal structure of Popocatépetl volcano is still unclear. In this work, we propose the first 3D velocity model of Popocatépetl volcano, describing the whole edifice inverting group velocity dispersion curves. We used data recorded at 39 broadband seismic stations installed in different epochs. We computed ambient noise cross-correlations, which were computed using two methods to increase the information for the modeling. Our results suggest the presence of a mushroom-shaped Popocatépetl’s system composed of two high shear wave velocity regions, the first one located at 5-0 km a.s.l., the second one located at 4-7 km b.s.l., and a narrow ‘pipe-like’ conduit connects both. The shallow high velocities are related to old and young volcanic structures due to mixed magmatic materials, which are affected by an intense degassing process that increases the magma viscosity and crystal content. The deepest reservoir is interpreted as a magmatic body that is confined due to the lithostatic pressure. The intermediate region is considered a narrow pipe conduit, where there is a low-velocity layer at the same depth. Moreover, our model reveals evidence of buried volcanic paleo-structures and the remains of ancient collapses generated by previous eruptions.