Widespread landslides induced by the Mw 5.1 earthquake of 11 May 2011 in Lorca, SE Spain

On 11 May 2011, a moderate magnitude (Mw 5.1) earthquake struck the city of Lorca (SE Spain) and nearby areas, causing notable damage, injuries and fatalities. Field inspection of the area affected allowed the location and characterization of more than 250 induced landslides, mainly of disrupted type (rock/soil falls, disrupted soil slides and rock avalanches). This number was very high when compared with the inventories of previous events of similar magnitude (Mw 4.7 to 5.0) in the zone and with the results of previous models for predicting slope behavior during earthquakes. Several factors are proposed here to explain the observed differences: (i) the comparatively high magnitude (Mw 4.5) of a foreshock of the seismic series that may have weakened the slopes; (ii) the high peak ground motion values recorded for these events and (iii) the occurrence of topographic site effects. The results of this study point out the importance of including such effects as improvements in the models for studying the regional behavior of slopes.