Estimation of ground subsidence in the city of Morelia, Mexico using Satellite Interferometry (INSAR)s

Abstract

In recent years, the city of Morelia, in central Mexico, has been affected by differential subsidence of the soil evidenced by faults and fractures on the ground. The goal of this study is to obtain ground deformation time series from InSAR interferograms, in order to determine the temporal and spatial evolution of subsidence in the city of Morelia. Twentyeight ENVISAT-ASAR images, acquired from May 2003 to September 2010, were processed. Perpendicular and temporal baselines of less than 400 m and 420 days respectively, were used as criteria to select interferograms. From a total of 378 interferograms, only 65 were considered to be of sufficient quality, based on the observed signal decorrelation. The results show that most of the city of Morelia is not affected by significant subsidence. In the areas where subsidence occurs, the rates of subsidence vary between 0.7 and 5 cm/yr. Most of the subsidence is in the form of discrete circular patterns and along segments of the observed surface faults. Ground subsidence is concentrated in specific areas on the footwalls of La Colina, Central Camionera and La Paloma faults. Subsidence, however, is not continuous along these faults, but observed only in some segments. In some cases, as in the case of La Paloma fault, the subsidence appears to be directly associated with the strong lithological contrast between the footwall and the hanging wall. In the other two cases, such as the Central Camionera and La Colina faults, the differential subsidence observed appears to be related with the complex basement and sedimentary structure of the volcanic subsoil of the city of Morelia and related primarily to differential compaction of the sedimentary fill.