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

Abstract

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.