Monitoring subsidence in Mexico City with ambient noise

Located mainly on thick lacustrine sediment, pumping ground water has led to pronounced subsidence in Mexico City, with a rate of nearly 0.35m per year in the worst affected locations. The load of new infrastructure exacerbates the problem. Monitoring the subsidence is crucial for understanding the mechanism and hazard prevention. While InSAR and other methods have provided highly resolved subsidence maps, they lack depth resolution.Seismic velocity, which reflects the state of the sediment (e.g. its stress, pore pressure, and other properties), will change with the compaction during the subsidence. Taking advantage of the omnipresent urban ambient noise recorded by the 30 broad band seismic stations in periods between 2010 and2021 around Mexico City, we calculate the cross correlations between different station pairs to determine the seismic velocity variations with coda wave interferometry in different frequency bands. We aim to obtain the spatial and depth distribution of seismic velocity variations using coda wave sensitivities and surface wave dispersion Previous studies have explained the long durations of ground-motion that has been observed during teleseismic and local earthquakes by higher-mode surface wave propagation in the competent rocks underneath the Mexico Basin, which has important implications for the depth sensitivity of any observed velocity changes.To determine the precise relationship between the subsidence and seismic velocity variations, we will further analysis the tectonic and environment effects. Our study aims to provide a more comprehensive understanding of the subsidence in Mexico City.