Studies of focal mechanisms and seismotectonic deformations of the Anatolian plate (Turkiye)

N. A. Sycheva

Vestnik KRAUNC. Fiziko-matematičeskie nauki, Tome 45 (2023) no. 4, pp. 147-165

Résumé

The work investigated the focal mechanisms and seismotectonic deformations of the Turkish crust, the tectonics of which is determined by the relative movements of the African, Aegean, Arabian, Anatolian, Black Sea and Eurasian plates. Data on focal mechanisms are collected from various sources and contain information on 847 earthquakes that occurred from 1976 to 2023. The study area is characterized by a variety of focal mechanisms. Some characteristics of focal mechanisms for three samples are considered: all events, western and eastern parts of Turkey. The calculation of the STD was carried out on the basis of the approaches proposed in the works of Yu.V. Riznichenko and S.L. Yunga. Studies of the direction of STD are based on data on the focal mechanisms of the 847 earthquakes. Earthquakes in Turkey occur to depths of 170 km. The majority of earthquakes occur to depths of 40 km. For two depth ranges – 0-40 km and deeper than 40 km, STD maps and the distribution of the Lode–Nadai coefficient were constructed. Using STD maps, the change in the direction of the shortening axes was determined, which varies from submeridian in the east to sublatitudinal in the west of Turkey, and the diversity of deformation conditions in the study area was noted. For the most part, the horizontal shear regime prevails in Turkey (eastern and central parts). The normal mode appears in the southwestern part. The western part of Turkey and the southern part of the East Anatolian fault zone are characterized by a transtension mode. Lake location area Van is characterized by a transpression mode. According to the distribution of the Lode – Nadai сoefficient a significant part of the territory is characterized by simple shear deformation, the western part of Turkey experiences deformation with a predominance of simple extension, and in the vicinity of Lake Van – deformation with a predominance of simple compression.

Détail

Keywords: earthquake, focal mechanism, lengthening and shortening of deformation axes, STD intensity
Mots-clés : principal stress axes, STD modes, Lode – Nadai сoefficient.

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