MAPPING OF S-WAVES ATTENUATION FIELD AT EAST KAZAKHSTAN AND WEST ALTAY REGIONS BY DATA OF MKAR SEISMIC STATION

We are analyzing recordings of local earthquakes in the regions of Eastern Kazakhstan and Western Altay, obtained by stations MAKZ and MKAR. We consider correlation dependence of maximum amplitudes ratio for Sn and Pn waves (Sn/Pn parameter) on distance. On the base of this dependence mapping of S wave attenuation field in the lithosphere of this region is carried out. A special attention is paid to high attenuation zones, comparison with seismicity is carried out. It is established, that the highest attenuation corresponds to the rupture zone of large Chu earthquake of 2003 (Mw=7.3). Besides, an anomaly of high attenuation is found in the area of Semipalatinsk test site (STS) and to the south of it. We discuss reasons of high shear wave attenuation in rupture zones of large earthquakes, and also within some sections of the STS.

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