Geophysical investigations of seismically induced surface effects: Case study of a landslide in the Suusamyr valley, Kyrgyzstan

In summer 1998, a geophysical survey including seismic profiles and electri cal tomography has been carried out in the Suusamyr valley, Kyrgyzstan. The scope was to investigate surface effects induced by the Ms = 7.3 Suusamyr earthquake, the 19th of August, 1992. In this paper, special attention is p aid to the case study of a debris slide triggered by the earthquake. Seismi c data are analysed by P-wave refraction technique and by surface wave inve rsion. Electrical tomographic profiles are processed by 2D-inversion. Using geotechnical and geological information, P-velocity models and resist ivity sections are interpreted in terms of geological materials, in order t o build a geological 3D model. On the basis of the latter, we carried out s tatic finite element computations as well as static and pseudo-static calcu lations with Janbu's method. Newmark displacement was computed, considering or not the influence of the shallow soft deposits. The results are compare d to the real displacement observed in the field and conclusions are drawn about the mechanism of the landslide.