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CONSTRUCTION OF THE HIGH-VELOCITY MODEL OF THE EARTH’S UPPER CRUST OF THE EURASIAN AND OKHOTSK SEA PLATES CONJUNCTION ZONE ALONG THE NORTH-EASTERN SEGMENT OF THE 3-DV PROFILE BASED ON THE RESULTS OF DIGITAL PROCESSING OF COMPRESSIONAL- AND SHEAR-WAVE REFRACTIONS

P. O. Polyanskiy 1, A. F. Emanov 1, A. S. Salnikov 2

1 Altai-Sayan Branch of Federal State Budgetary Institution of Science of the Geophysical Service of the RAS, Novosibirsk, Russia; 2 Siberian Research Insitute of Geology, Geophysics and Mineral Resources, Novosibirsk, Russia

An automated algorithm for monitoring the areas of refraction event tracking along the profile based on the dynamic conversion method is developed. Time sections of compressional - and shear-wave refractions recorded by the CDP shooting geometry on the North-Eastern segment of the 3DV survey base line are constructed. A high-speed model of the upper part of the Earth’s crust is constructed to depths of ≈2 km in the conjunction zone of the Okhotsk and Eurasian lithospheric plates. According to increased values of the velocity ratio of P- and S- waves, it is found that refracting boundaries in the Ayan-Yuryakh block are sections of rocks with various lithological composition in sedimentary cover. The zone of reduced values of P-wave velocity and the VP /Vs ratio associated with a high fragmentation of rocks is identified on the high-velocity profile of the Chay-Yurya fault zone, both above and below the refracting boundary. The velocity values of P- and S-waves (6.0–6.1 km/s and 3.6–3.7 km/s, respectively,) and reduced values of the Vp /Vs ratio (≈1.65) concerned with intrusions of acid rocks were recorded in the southern part of the Inyali-Debin block within t he depth range of 1–1.5 km.

Keywords: boundaries of lithosperic plates, Ayan-Yuryakh block, Inyali-Debin sinclinorium, geophysical survey base line 3-DV, method of dynamic conversion, compressional-wave refraction and shear-wave refraction, velocity models of the Earth’s crust, time sections, coherent waves.

DOI 10.20403/2078-0575-2023-1-21-35

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