VELOCITY AND DENSITY HETEROGENEITIES OF THE TIEN-SHAN LITHOSPHERE

The Tien-Shan orogene is a region in which the earth's crust undergoes considerable thickening and tangential compression. Under these condi tions the lithosphere heterogeneities (composition, rheological) creat e the prerequisites for the development of various phenomena of tecton ic layering (lateral shearing, different deformation of layers). To st udy the distribution of velocity, density and other elastic parameters , the results from a seismic tomography study on P-wave as well as S-w ave velocities were used. Using empirical as well as theoretical formu las on the relationship between velocity, density and silica content i n rocks, their distribution in the Tien-Shan's lithosphere has been ca lculated. In addition, other elastic parameters, such as Young's modul us, shear modulus, Poisson's ratio and coefficient of general compress ions have been determined. Zoning of different types of crust was carr ied out for the region investigated. The characteristics of the ''crus t-mantle'' transition have been investigated. Large blocks with differ ent types of the earth's crust were distinguished. Layers with inverse values of velocity, density and shear and Young modulus are revealed in the Tien-Shan lithosphere. All of the above described features open new ways to solve geodynamics problems.