Subsidence and Morphologic Variations in Mexico City Generated by the Earthquakes of September 2017

Abstract

Two earthquakes that occurred in southwest Mexico generated subsidence and morphologic changes in the area of Mexico City. To study the subsidence, an interferometric procedure was carried out using four interferometric pairs acquired from the radar satellite Sentinel-1 in IW (Interferometric Wide Swath) TOPS (Terrain Observation by Progressive Scan) SLC (Single Look Complex) mode. Four interferograms and four displacement maps were generated. To quantify the morphologic changes, a synergism of the Sentinel-1 radar bands in IW GRD (Ground Range Detected) mode and the SPOT 6/7 optical bands was considered. The synergism consists of a hybrid image formed by the radar bands and the optical bands. Principal component analysis was applied to the bands of the hybrid image. The first three components were retained, and a divergence operator was then applied to the vector field formed by these components, producing a texture map. The texture map was evaluated in conjunction with the interferogram and displacement map for the September 2017 earthquakes. Results indicated a complex pattern of subsidence and morphologic changes. The interferogram and subsidence of September 2017 correlated with a map of earthquake damages.