ИСТИНА

A review of seismicity of the Lena-Anabar Trough and adjacent territories (Northwestern Yakutia) recorded during the instrumental period of observations (1963-2022) by stationary stations of the Yakutsk branch of the FIC EGS RAS is presented. The seismicity distribution is analysed in connection with the known tectonic setting, spatial characteristics of the magnetic and gravity fields, as well as with the peculiarities of the deep structure of the region revealed by the results of 3D spectral inversions of potential fields and 2D inversions of profile magnetotelluric data based on the corresponding seismic sections. The analysis uses potential field maps (generalisation of 1:200,000 scale survey materials) and oil and gas prospecting MTZ data from a network of regional MOGT2D profiles. The main tool for detecting anomalous characteristics of geophysical fields, as well as elements of the depth structure in their correlation with the spatial (and partially known depth) picture of seismicity distribution is the modern GIS complex INTEGRO (VNIGNI, Geoinfomatics Department). When detecting and verifying these correlations, an integrated approach using geophysical fields of different nature and a variety of their morphological and statistical parameters was very important, which allowed us to identify with sufficient certainty seismic generating structures, both separate and forming WHO zones (e.g., within the seismically most active section of the Lena-Anabar marginal suture in the Lena River delta). It is shown that the increased seismicity mainly corresponds to the areas of anomalous gradients of potential fields and zones of transition from isolating to conducting areas on geoelectric sections, diagnosing heterogeneities of geological structure. Using special methods of local linear anomalies extraction, morphological characteristics of potential fields were established, which can be associated with previously unknown seismotectonic elements in the most submerged part of the Lena-Anabar trough – fault zones of north-west strike. Earthquake source mechanisms have been determined for some of the most intense, confidently recorded events confined to the identified seismogenic structures.