Monitoring land subsidence and its induced geological hazard with Synthetic Aperture Radar Interferometry: A case study in Morelia, Mexico

Twenty three ENVISAT Synthetic Aperture Radar (SAR) images acquired in 2003–2010 were processed with conventional SAR Interferometry (InSAR) and Persistent Scatterer Interferometry techniques, to investigate spatial and temporal patterns of land subsidence in Morelia, Mexico. Subsiding areas are distributed as either concentrated circular patterns corresponding to intense groundwater extraction (e.g., Rio Grande meander area; maximum deformation of 7–8 cm/yr) or as elongate patterns oriented along NE–SW or E–W directions and parallel to major faults (i.e. La Colina, La Paloma and Central Camionera; maximum deformation of 4–5 cm/yr). High subsidence rates are also measured on the hanging wall of major normal faults, where the thickest sequences of compressible Quaternary sediments crop out. Strong contrasts in subsidence rates are identified across major faults, suggesting that these faults act as barriers to horizontal movement of groundwater. Subsidence rates show a weak positive correlation with the total thickness of compressible deposits, while there is no correlation with either water extraction rates or changes in static water level. Time-lapse analysis of ground deformation with conventional InSAR reveals temporal variations of subsidence north of the La Colina fault and the Rio Grande meander area. For this latter area, cross sections and 3D perspectives of InSAR measures, and analysis of subsidence rates through time, show an acceleration of subsidence velocities since 2005, corresponding to recasing of the Prados Verdes II well, whose location is centered in the area of highest subsidence.

► Present-day subsidence in Morelia, Mexico, is analyzed through ENVISAT InSAR and PSI.
► Circular patterns of subsidence correspond to intense groundwater extraction sites.
► NE–SW or E–W oriented subsidence patterns, parallel to main faults, are observed.
► Hanging walls, whose compressible sediments are thicker, subside faster than footwalls.
► Non-linear variations are observed N of La Colina fault and in the Rio Grande meander.