Seismotectonic model of the Verkhoyansk-Kolyma orogenic region (Northeast of Russia)

Abstract

Verkhoyansk-Kolima orogenic region (VKOR), which located in the North-Eastern part of the Russia, is marked by a high seismic activity. In this region more than 20 thousand earthquakes are registered. The centers of the earthquakes are placed in the whole interval of the Earth's crust (4-40 km), while most of seismic activity is in the middle and upper of her layers. In the problem of creation of the seismotectonic model of the VKOR Earth's crust the active faults of the sedimentary complex are best of all studied, at the same time the role of the structure elements of crystally basement is practically not investigated. The article begins with the description of the located conformity to natural laws in the centers of strong earthquakes ($M>5$) with elements of the VKOR crystal basement structure. The block structure of the Earth's crust, which was well grounded on the results of the complex interpretation of the gravity and magnetic fields with take attention of the petrophysics criterions structure-material complexes is chosen as basis model. The VKOR crystal basement contain the north-eastern part of the Aldan-Stanovoy geoblock and Verkhoyanskiy geoblock, which consist of the North-Verkhoyanskiy, South-Verkhoyanskiy, Adiacha-Nerskiy and Ayan-Uriakhskiy megablocks. Maximal number of the VKOR strong earthquakes are registered on the Adiacha-Nerskiy megablock territory. Tectonic faults of the Adiacha-Nerskiy megablock have north-western strike such as strike of Eastverkhoyansk sutura, which delimited the North-Asia craton and Kolyma-Omolon microcontinent. This allow to offer, what forming of the Adiacha-Nerskiy megablock structure take place in the conditions of the Mesozoic collision between North-Asia craton and Kolyma-Omolon microcontinent. The process of the interaction of this tectonic structures, evidently, continues also at the present time, what is the reason of the forming in the Earth's crust fields of the tectonic strains and their relaxation on account of earthquakes. The results of this research make new data for the construction of the Earth's crust seismic-tectonic model on the level of its upper and middle parts. It is shown that the most seismo-dangerous territory is the central part of zone of the Eastverkhoyansk sutura, which controlled centers of the Andrey-Tassky (22.06.2008, $M=6.1$) and Abiyskiy (14.02.2013, $M=6.9$) earthquakes.