Seismic refraction and ambient noise methods to explore the extension of soft materials in a landslide

Abstract

A portion of the west of Mexico City is a densely populated area located in an abrupt topography, whose volcano-sedimentary materials increase the likelihood of landslides. This study uses Seismic Refraction Tomography (SRT) and Ambient Noise Tomography (ANT) methods to estimate the extent of landslide-prone materials at a test site. We exploited the geometry of a quadrangular array of surface sources and receivers to generate a Vp tomography image of the bedrock and surface-wave group-velocity tomographies of SRTand ANT in the frequency range of 6 to 26 Hz. We found that the best velocities correlation between the two methods is an average frequency of 24 Hz. The results show the areas of low velocity associated with materials that have lost their resistance due to the increase in pore pressure (Vs < 100 m/s) and the areas where eventually more landslides will occur (120 < Vs < 200 m/s) if mitigation work is not carried out. The most stable zones correspond to materials with velocity values greater than 250 m/s that overlap a substratum at an average depth of 8 m. In the case of a high risk of landslide, when it is not advisable to perform active source experiments, ANT can provide good results to determine the extension of the sliding materials.