The Features of the Deep Velocity Structure of the Trans-Baikal Section of the Central Asian Fold Belt from the Seismolo
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Features of the Deep Velocity Structure of the Trans-Baikal Section of the Central Asian Fold Belt from the Seismological and DSS Data (Alignment of the 1-SB Reference Profile) V. M. Solovyeva, *, A. S. Salnikovb, **, V. S. Seleznevc, ***, V. V. Chechelnitskyd, ****, A. V. Liseikinc, *****, and N. A. Galevaa, ****** aAltay-Sayan
Branch. Federal Research Center of the Geophysical Survey, Russian Academy of Sciences, prosp. Akad. Koptyuga 3, Novosibirsk, 630090 Russia b Siberian Scientific Research Institute of Geology, Geophysics, and Mineral Resources Joint Stock Company, Krasny pr. 67, Novosibirsk, 630091 Russia c Seismological Branch, Federal Research Center of the Geophysical Survey, Russian Academy of Sciences, prosp. Akad. Koptyuga 3, Novosibirsk, 630090 Russia dBaikal Branch, Federal Research Center of the Geophysical Survey, Russian Academy of Sciences, ul. Lermontova 128, Irkutsk, 664033 Russia *e-mail: [email protected] **e-mail: [email protected] ***e-mail: [email protected] ****e-mail: с[email protected] *****e-mail: [email protected] ******e-mail: [email protected] Received July 25, 2019; revised October 25, 2019; accepted May 19, 2020
Abstract—The materials of deep seismic studies carried out on the 1-SB reference geophysical profile and the areal interpretation of the seismological data obtained in the Trans-Baikal part of the Central Asian Fold Belt are presented. It is shown that longitudinal and transverse waves were recorded from the reference boundaries within the crust and the Moho surface in the Trans-Baikal region using explosions and powerful vibration sources on the 1200-km long 1-SB geophysical profile. The inhomogeneous upper crust velocity structure down to 15–20-km depths and the Moho surface was revealed from P- and S-waves. The anomalous mantle, which exhibited decreased boundary velocity values of P- and S-waves at 7.8–7.95 km/s and 4.3–4.5 km/s, respectively, was reliably traced within the Baikal Rift Zone from the DSS and seismological data. In the southeastern part of the area (the central Mongol-Okhotsk Orogenic Belt and adjacent folded structures of the Trans-Baikal region) a layer of increased P-and S-wave velocity values of 8.4 ± 0.15 km/s and 4.9 ± 0.05 km/s, accordingly, was detected at the mantle surface. A comparison was made with the materials of other studies. Keywords: DSS profile, P- and S-wave velocities and velocity ratios, deep seismic section, Earth’s crust, Moho, seismological data, Central Asian Fold Belt, Transbaikalia DOI: 10.1134/S1819714020050073
INTRODUCTION The Transbaikalia study area is located within major tectonic structures of the Central Asian Fold Belt comprising the Baikal Rift Zone, the MongolOkhotsk Belt, the East Transbaikalia, and SayanTransbaikalia folded areas [4] (Fig. 1). The western and northwestern parts of the territory within the Baikal Rift Zone (BRZ) have been studied in detail using seismic methods [5–7], while the eastern part of Transbaikalia has remained poorly studied [6, 7].
During 2014–2015, comprehensive geological– geophysi
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