Enhanced Local Earthquake Tomography at the Popocatépetl Volcano (Mexico)

Popocatépetl, one of Mexico's most active and hazardous volcanoes, threatens millions living in its shadow. Since its reactivation in 1994, several seismic tomography studies have been conducted. However, their results show significant inconsistencies, fueling debate about the volcano's internal structure. This study presents new findings from an enhanced local earthquake tomography with data from 2019 to 2024.

We used a seismic network comprising up to 18 broadband stations. Ten of these stations belong to the National Center for Disaster Prevention (CENAPRED) and form the volcano’s permanent monitoring network. The remaining eight are managed by us at the Institute of Geophysics at UNAM. The spatial distribution of these stations ensures adequate azimuthal coverage of the volcanic edifice and its seismicity, enabling the highest depth resolution achieved to date.

The local earthquake database was created using a machine learning-based workflow. This involved automatic phase picking and association, followed by post-processing to refine the VT catalog. This approach identified additional events absent from CENAPRED’s official catalog, improving ray coverage across the region. We then applied Enhanced Seismic Tomography, combining Double-Difference Tomography with the Weighted Average Model post-processing to minimize bias from initial parameters.

Over 1,000 events were jointly inverted to produce three-dimensional P- and S-wave velocity models and relocations. Resolution tests indicate the ability to resolve structures of approximately 1×1×0.5 km, offering unprecedented detail of the volcano's features. Finally, we compare our results with previous models to refine our understanding of Popocatépetl’s interior.

 

This research was supported by the UNAM-PAPIIT Program: IN103823.