Impact of rainfall, atmospheric pressure, and temperature on seismic velocity variations at different depths in Volcán de Colima, Mexico using Noise Interferometry

Abstract Earth’s crust is subject to changes triggered by various processes occurring both over (i.e. weather variations), and under (i.e. magmatic, tectonic) the surface simultaneously. Seismic noise interferometry technique allows us to monitor these physical changes by retrieving the relative seismic velocity changes (dv/v). However, detailed analysis is usually needed to differentiate which processes contribute to the final variation of dv/v to produce an accurate monitoring of the upper crust. In this work, we analyzed the daily dv/v in the volume surrounding Colima Volcano calculated using the single-station cross-component (SC) method on seismic records from 2013-2017. We focused on two frequency bands (0.1-1, 1-2 Hz) to retrieve velocity changes at different depths (4 and 1 km, respectively) and compare their differences. Both dv/v signals showed co-seismic velocity drops and annual variations. Using wavelet transform coherence, we found that three environmental parameters—rainfall, temperature, and atmospheric pressure—might influence the temporal variation of dv/v. To correct the dv/v time series, we fitted two models based on: 1) rainfall-induced pore pressure coupled with barometric variations and 2) thermoelastic strains. By comparing the calculated and corrected dv/v signals, we observed that atmospheric pressure-induced velocity variations are neglectable. Rainfall-induced pore pressure can cause velocity drops, especially on the 1-2 Hz signal. Thermoelastic strains seem to cause variations up to +/-0.5% on both band frequencies. These observations support previous hypotheses about rain causing dv/v changes in the top hundreds of meters of the crust, while thermoelastic strains can propagate and induce dv/v variations at greater depths.