Shear wave velocity structure for seismic microzonation of Lorca town (SE Spain) from MASW analysis

The average shear-wave velocity to a depth of 30 m (Vs30) has been obtained in the Lorca town (SE Spain). Measurements of Vs30 were made using the Multichannel Analysis Surface Waves (MASW) method. Those Vs30 values let us classify the urban area of Lorca town according to both the EC8 and the NEHRP site class. Then, these zones were related to the shallow geology of the town. Regarding the damage distribution in Lorca town due May 11th, 2011 Lorca earthquake, the most affected buildings were located on zones classified by the EC8 as B2 (from 360 m/s to 500 m/s) or C (from 180 m/s to 360 m/s). The geology in those zones is predominantly composed of shallow layers of Holocene unconsolidated sedimentary filling (including colluvial, aluvials and anthropogenic fillings) and layers of Pleistocene consolidated sedimentary fillings of glacis. Areas of the town composed of Tertiary (Neogene) medium hard rock were found Vs30 values above 500 m/s (zone B1) and where the building damages were not relevant.