Monitoring Spatiotemporal Seismic Velocity Changes Using Seismic
Interferometry and Distributed Acoustic Sensing in Mexico City
Abstract
Distributed Acoustic Sensing (DAS) offers a transformative solution for
dense, high-resolution seismic monitoring to address the challenges of
traditional seismometers in urban seismic surveys. Here, we employ
seismic interferometry of the ambient noise field and the trace
stretching method to monitor seismic velocity variations in Mexico City.
We present spatiotemporal variations in relative Rayleigh wave group
velocity (dU/U) calculated over two frequency bands (0.4-1.2 Hz and
1.2-3.6 Hz) using DAS data collected over a year. To investigate these
variations, we model the impacts resulting from the 2022 Mw7.6
earthquake, along with the effects of precipitation and temperature on
the dU/U calculated in the 0.4-1.2 Hz frequency band, which is primarily
dominated by the fundamental mode of the Rayleigh waves. Our results
indicate that the earthquake-induced velocity drop differs in certain
fiber sections, likely due to their non-linear soil behaviors and
co-seismic stress changes but without relation to the maximum local
deformation registered during the earthquake. Additionally, our modeling
indicates that the velocity changes are influenced by seasonal
temperature variations, and the impact of precipitation is relatively
minor, at least for the depth range (<~50 m)
examined in this study. This study highlights the capability of DAS to
enhance spatiotemporal monitoring in urban environments, providing
valuable insights into both seismic and environmental responses.