Modelos dinámicos de rotura de los escarpes calizos sobre las avalanchas de roca en la Sierra de la Sobia versus riesgo sísmico

Resumen

We have investigated the mechanical instability of four limestone rupture scarps that lie onto the western and southern hills- lope of Sierra de la Sobia (Asturias, NW Spain). The rupture scarps are developed onto limestone of Carboniferous age (Val- deteja Formation) and have planar geometry controlled by active small strike-slip faults, with lengths smaller than 3 km, that are trending parallel or transverse to the arcuate trace of the range. 350 mechanical discontinuities orientations have been measured along of the depletion slopes and classified in order to analyser which are critical or stables for four dynamical failure modes: planar sliding (PS), wedge sliding (WS), direct toppling (DT) and flexural toppling (FT). The architecture of the rupture slopes is stable mechanically, according to the low risk for failure modes (< 14 % by PS, < 26 % by VS, < 30 % by DT and < 25 % by FT). However, if horizontal seismic accelerations rise values ranging between 0.1 and 0.15 g, then the corresponding safety factors decrease below 1.3 and rupture scarps could become unstable. New events of rock avalanche seem to be probably with this results, since Sierra de la Sobia is a seism-active zone of the Cantabrian Mountains and acce- lerations modelled are into the range of peak ground acceleration that the 2013 European Seismic Hazard Map predicts for NW Iberia. Moreover, unstable huge relict reliefs are still above some of the accumulation zones.