Investigation of deep seated gravitational slope deformation in the Sartal and Kuh-e-Sefid anticlines:Northwest of Dehdasht

The area of Charousa and Lendeh in the Kohgiluyeh and Boyer-Ahmad province in southwestern Iran is geologically part of the folded Zagros. In this area, the core of the Kuh-e-Sefid and Sartal anticline of the Ilam-Sarvak limestone are the main high altitudes of the region. At these altitudes the scar of large landslides and evidence of deep seated gravitational slope deformation are visible. The largest of these are the Almor landslide in the Sartal anticline with an approximate volume of over 600 million cubic meters. In this study, the evidence of deep seated gravitational slope deformation of these anticlines has been investigated and the causing factors for Almor landslide have been determined. To investigate of this issue, a combination of geological field survey, image processing studies, and laboratory studies of rock mechanics and soil mechanics were used to prepare preliminary data. This data are processed and analyzed by a combination of kinematic analysis, limit equilibrium sensitivity analysis, and finite element numerical modeling. Finally, a three-dimensional geological model is proposed to illustrate the proposed mechanism for this landslide. According to this study, a combination of deep seated gravitational slope deformation, along with wedge failure and three hinge buckling, was the causes of this avalanche.