Summary Distributed Acoustic Sensing (DAS) using metropolitan telecom fibre-optic cables provides an unprecedented opportunity for seismic monitoring in sedimentary basins, exemplified by Mexico City. In this study, we analyze 15 months of nearly continuous DAS measurements to identify previously undetectable details of wave propagation, thereby enabling the precise localization of local earthquakes. Using real seismic velocity models, we overcome the inaccuracies of traditional constant {VP}/{VS} approaches, highlighting significant limitations of Wadati diagrams in sedimentary environments. Our results reveal clear hydro-seismic coupling, where intense early-season rainfall, coinciding with low aquifer levels, generates sufficient stress perturbations to trigger moderate-magnitude earthquakes (Mw ∼ 3. 5). These main events subsequently induce slow slip along local faults and secondary seismicity on a perpendicular plane, driven primarily by stress imbalance rather than fluid involvement along faults. We further identify basin-converted and conical phases as dominant sources of ground shaking, underscoring the urgent need to integrate these secondary seismic phases into urban seismic hazard assessments and building codes. Our findings underscore the crucial role of continuous DAS measurements in comprehending urban seismic risk and managing aquifer resources, thereby establishing a robust monitoring framework with global applicability in sediment-filled megacities.
Perton et al. (Wed,) studied this question.