Characterization of the shear wave velocity in the metropolitan area of Málaga (S Spain) using the H/V technique

Abstract

The H/V technique is used throughout this research to characterize the soil column at different locations of the metropolitan area of Málaga (Southern Spain). This region stands as a good example of a continuously growing zone, mostly developed on soft alluvial sediments, with moderate to low seismicity. The H/V analysis of the noise measurements reveals frequency peak values ranging from 3 to 4 Hz on the NE of the study area, where the basin basement outcrops, to 0.3 Hz in the Guadalhorce River alluvial plain. We correlate the presence of the main H/V peak with the appearance of the basin basement materials in the sedimentary column; whereas secondary peaks obtained in some measurement points may be related to Quaternary and Pliocene sedimentary fill. Shear wave velocity profiles, inverted from the experimental H/V curves, data available from previous boreholes and superficial geology information are all integrated to provide four characteristic 2D cross-sections of the basin. In the ground model described here we distinguish four layers: a shallow layer that is probably linked to the recent Quaternary sediments (Vs from 100 to 500 m/s); an intermediate layer that is related to the presence of late Pliocene materials (Vs from 300 to 1000 m/s); a deep layer associated with early Pliocene materials filling the trough formed by the basin basement (Vs from 700 to 1600 m/s); and finally the basement formation that shows stable velocity at around 2000 m/s.