Source location of the earthquake of February 23, 2023 on the block structure background of the Pamir

The results of a study of lateral inhomogeneities in the attenuation field structure in the focal zone and in immediate vicinity of the earthquake of February 23, 2023 with Ms=7.1 using the short-period coda method are discussed. This earthquake is one of three seismic events with a magnitude greater than 7.0 that occurred in Pamir over the past 110 years. In most of the territory of the studied region, the quality factor QS of the upper mantle is about 400. Against this background, linearly elongated low-quality zones with QS=300 gravitating towards the main fault zones, and small isometric blocks with quality values of 500–1000 stand out. The obtained results are in satisfactory agreement with the main fault zones of the research area, with the results of studies of the deep structure of this territory by other methods, in particular, magnetotelluric and seismic tomography. Lateral inhomogeneities of the attenuation field are the basis for ideas about the block structure of the region (the relative position of blocks with a high QS-factor and weakened zones). Based on these data, variations in the block structure of the region under study were analyzed in connection with several significant earthquakes (with a magnitude of more than 6.0) in Pamir. It is shown that the process of preparation of the most noticeable earthquakes of recent years ended with the formation of large consolidated blocks consisting of several small ones. The scenarios of preparation and development of the considered strong events illustrate the role of ascending flows of deep fluids in seismogenesis processes under conditions of changing impacts of external factors of planetary scale, such as variations in the Earth's rotation speed.