Calculation of the hodograph for Tiva region on the basis of velocity model of media

The development of seismic network in Krasnoyarsk region and Tiva republic arouse the interest to earth crust structure model for local earthquake data processing. The seismic waves travel time hodograph as 1-dimensional model of media structure is widely used in seismological practice. In the present paper the results of calculation of the first arrival times of P-wave hodograph for Tiva region are presented. Calculations are based on the block-layered velocity model of media obtained earlier as a result of seismic research of Altay-Sayan folded area data. A brief description of earth crust and upper mantle velocity model for south part of Krasnoyarsk region and Tiva republic is given. The structure of Tiva block is supposed to be 3-layered with horizontal boundaries. Consolidated part of the earth crust is characterized by linear dependence of wave velocity on depth. Values of model parameters were obtained by averaging of DSS and CWME velocity curves. Analysis of the wave pattern in the framework of the media model is carried out. In the paper an algorithm to calculate of seismic rays from sources positioned in different depths within the earth crust is discussed. The algorithm is based on analytical solutions derived from the general formulation of the direct kinematic problem of seismology in the ray approximation. The refracted and head waves propagation in the environment model is considered. Resulted hodograph is compared to that applied recently to regional seismic data. Comparison of head wave hodograph allowed to reveal a systematic error due to a difference in the earth crust thickness. Comparison of refracted P-wave hodograph with experimental travel time catalogue from industrial explosion shows a good agreement. A way to insert station corrections into hodograph originated from low velocity sediments under the seismic stations is proposed. Obtained hodograph is offered to use in hypocenter location problems.