Mass movements at Zapotitlán de Mendez, Puebla: relation between lithology and type of mass failure

Abstract

At the end of September and at the beginning of October 1999, the Northern Sierra of Puebla (Pue.) was affected by thousands mass movements. The tropical depression number 11 provoked heavy rains with a maximum peak during October 4 and 5. The town of Zapotitlán de Méndez was affected by two different types of mass movements: 1) superficial slide of volcanic soil, and 2) rotational landslide in folded shales. This study evidences that the soil–slide processes were of low magnitude and did not directly affect the human settlements. In contrast,  the deep rotational landslide process is directly associated with structural debility of the relief, promoted by the dipping of the deformed beds in slope direction. By knowing the relationships between the dip of rock bedding and the geometry of the relief, it is possible to determine the degree of susceptibility for the area and to establish an evacuation plan in ca se of a new meteorological event such as that one occurred in 1999.