The large deep-seated landslide induced by the March 12th, 2012 rainfall event in the city of Azazga, Northern Algeria: deformation characteristics and failure mechanisms

A rainfall-induced deep large landslide occurred on March 12, 2012, in the city of Azazga (Northern Algeria), causing heavy damages to residential buildings and public infrastructures. In this work, we investigate inventory mapping, deformation characteristics, controlling factors, failure mechanisms based field investigation, aerial photographs satellite images interpretation, boreholes equipped with piezometers inclinometers, as well subsurface geophysical imaging by electric resistivity tomography (ERT). The obtained map shows that 2012 affected an area 0.40 km2. This is considered a partial reactivation pre-existing one (0.606 km2), which represents 6.65% total urban area. Moreover, analyses identified two types causative factors: (1) triggering factor related high intensity antecedent rainfall human activity through slope excavations embankments; (2) susceptibility factors lithological nature internal structure flysch deposits, their weak mechanical resistance presence shallow aquifers, basal undercutting erosion Iazoughen Aboud river torrents. inclinometer measurements ERT reveal complex, deep-seated rapidly moving whose surfaces are located at depth 11–29 m average velocity 1–29 cm year−1. entire slip surface along geotechnical interface between bedrock overlying scree. comprehensive study provides useful information landslides may constitute guidance for hazard mitigation prevention.