Geophysical methods for the investigation of landslides

Landslides occur extensively in all countries of the world. A landslide is a complex geologic body composed of a combination of layers having contrasting and gradational physical properties. In assessing the danger of landslides, it is of prime importance to investigate the structure of the landslide slope and its water saturation as well as the properties and status of the soils comprising the slope. The investigation and full evaluation of all these problems by traditional methods of engineering geology are sometimes impossible.Electrical and seismic methods are used to obtain the information needed to determine slope stability. Experience has been gained from long-term investigations carried out in various regions of the Soviet Union. Applications include evaluating geologic and hydrologic conditions related to the occurrence of landslides. Primary attention is devoted to the study of landslide slopes proper. The geologic structure of a landslide is considered in modeling it and determining the thickness of both the landslide body and the slip zone. The methods of self-potential, resistivity, and temperature measurement are analyzed for characterization of the seepage flow through the landslide body. Self-potential, resistivity, and temperature anomalies are associated with sites of increased landslide activity.Useful engineering properties of soils may be obtained from field and laboratory geophysical measurements. Measurement of changes of geophysical parameters with time are significant in assessing changes in the states of landslide soils.Observation of the direction and velocity of landslide movements is possible with magnetic and electrical methods.Examples of geophysical investigations of landslides in the Crimea, on the Black Sea coast of the Caucasus, and in the Volga River Valley are presented.