Deep Structure of the Northwestern Termination of the Caucasus from New Geological and Geophysical Data
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Structure of the Northwestern Termination of the Caucasus from New Geological and Geophysical Data E. A. Rogozhina, b, *, A. V. Gorbatikova, M. Yu. Stepanovaa, Yu. V. Kharazovaa, A. I. Sysolina, N. V. Andreevaa, V. V. Pogrebchenkoa, S. Yu. Chervinchuka, Jie Chenc, Jiao Liuc, A. N. Ovsyuchenkoa, and A. S. Lar’kova aSchmidt
Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, 123242 Russia Federal Research Center—Geophysical Survey, Russian Academy of Sciences, Obninsk, 249035 Russia c State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing, 100029 China *e-mail: [email protected] b
Received April 13, 2020; revised May 20, 2020; accepted June 9, 2020
Abstract—In 2014–2019, integrated geological and geophysical studies were carried out in the largest flexural-rupture and fold-and-fault zones of the Northwest Caucasus (the Anapa, Akhtyr, Moldavanovka, Karabetov, Fanagoria and Azov anticlinal ridges and the Pshekha–Adler, Kerch–Tuzla, and Kerch Strait faults). Microseismic sounding method (MSM) was the main geophysical approach. The MSM studies identified the deep structural features of the Earth’s crust in the study region and made it possible to correlate them with the specific tectonic structures on the surface. The correlation was established by reconciling the results of the MSM studies, the parameters of sedimentary cover section, and crustal discontinuities revealed by drilling and previous studies of the converted waves from the earthquakes. It is found out that the Anapa flexure and longitudinal tectonic zones have the distinct deep roots beneath them. The trans-Caucasian Anapa flexural-rupture zone separates the pericline of the Northwest Caucasus from the region of the Taman Peninsula, whereas longitudinal flexures and fault structures divide the meganticlinorium from the subsided West Kuban and Azov blocks of the northern slope of the folded system and from the Kerch–Taman trough of the southern framing of the Northwest Caucasus. The faults in the study region are distinguished into deep faults penetrating into the lower crust and even reaching the upper mantle and near-surface faults localized within the sedimentary cover in the Earth’s interior. The seismogenic role of these tectonic deformations in the studied seismic region is determined. Keywords: flexural-rupture zone, anticlinal ridge, mud volcano, Earth’s crust, tectonic disturbance, microseismic sounding, geophysical methods DOI: 10.1134/S1069351320060075
INTRODUCTION Integrated geological and geophysical study of the linear tectonic structures that are not expressed on the surface in the form of clear active faults is a promising research direction. An important point is that frequently, these structures are host to the sources of strong and moderate earthquakes as well as to mud volcanoes. For example, the strongest and strong earthquakes in Gazli (1976 and 1984, three events with М = 7.0, 7.3, 7.2), Kairakkum (1985, M = 5.7), Zaisan (1990, M = 7.0), Racha (1991, M = 7.0), Oni (2
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