Seismic basaltic structure under the local subsidence in San Lorenzo Tezonco, Iztapalapa, México, Distrito Federal

摘要

The purpose of this work is the structural determination of basaltic flows under the fractures presented in San Lorenzo Tezonco, Iztapalapa. A collapse event occurred on 7 July 2007. The geological characteristics of the zone are: clay, volcanic ash and basaltic rocks of the Yuhualixqui volcano. The seismic technique is a combination of both the seismic refraction method and the vertical reflections of the P wave on basaltic rocks. The results of refraction are: velocity values of 390–420 m/s for clay, and 680–850 m/s for volcanic ash. With the information of an old well: Santa Catarina 13, and the refraction results, we executed computational modelling. We obtained synthetic seismograms of vertical reflection of the P wave to distinguish the real time reflections. Then we calculated the depths of basaltic rock at each site of data acquisition. The result is a 3-D image of the basaltic flows and their implications in the phenomenon are working as a takeoff surface.