ИСПОЛЬЗОВАНИЕ МЕТОДОВ СЕЙСМОАКУСТИКИ НА ЗАКАРСТОВАННЫХ ТЕРРИТОРИЯХ КРУПНЫХ ГОРОДОВ (НА ПРИМЕРЕ МОСКВЫ И НИЖНЕГО НОВГОРОДА)

Abstract

Various geophysical methods are used to study the karst of carbonate massifs, the effectiveness of which in the conditions of large cities is low, since they are affected by intense industrial and transport disturbances. The paper discusses the use of seismic acoustic methods of ground and borehole geophysics: the method of the common depth point (CDP), the method of refracted waves (MRW), crosswell seismoacoustic sounding (CSS). It is shown that seismic survey methods provide more informative engineering-geological research. The use of a non-explosive source of excitation of seismic vibrations made it possible to carry out research in urban areas. As a result of the implementation of a system for accumulating useful seismic signals, informative material was obtained in areas of intense industrial interference. The resolution of seismic surveys on the mapping of coal deposits and the construction of maps of the paleorelief is clearly visible from a comparison of geological maps constructed from drilling data and taking seismic studies into account. In combination with crosshole seismic acoustic sounding, it is possible to fix relatively large karst cavities and destroyed zones. Complicating in the interpretation of seismoacoustic indicators is the fact that the carbonate massif is often a relatively evenly karsted system in the form of karst cavities of various sizes (mostly irregular in shape, filled or open), fracturing, cavernosity and porosity. As a result, the motley pattern of the distribution of the velocities of elastic waves is averaged, making it difficult to isolate low-velocity zones confined to karst cavities. Additionally, according to the data of microseismic logging — vertical seismic profiling (MSL — VSP), it is possible to identify low-speed zones associated with decompaction in the upper cover layer of rocks, from which sandy sediments are transported to a carbonate strongly karsted massif. Seismoacoustic sounding allows you to control the quality of grouting works when filling karst cavities with cement mortar.