Особенности сейсмического процесса в западной части Алеутской субдукционной зоны и их возможная связь с климатическими изменениями в Арктике

Abstract

In the second half of the XX century, there was a pronounced increase in the average annual temperature in the troposphere surface layer of the Russian Arctic region, which led to a scaling-up in the risks of natural disasters associated with the cryolithosphere degradation. Modern integrated studies of the Arctic have revealed a significant influence of geodynamic processes on the permafrost state. Previously, a seismogenic-trigger mechanism of the occurrence of climate warming phases in the Arctic proved to be possible due to strong mechanical disturbances of the marginal region of the Arctic lithosphere, caused by major earthquakes in the Aleutian subduction zone. The authors discuss the features of the seismic cycle in the Aleutian subduction zone, characterized the presence of a pronounced tangential component of the convergence vector of lithospheric plates. The study shows that the orientation of the plate convergence vector relative to subduction zone axis can have a significant impact on the preparation and occurrence of major earthquakes in subduction zones. In particular, the analysis of the seismic activity occurring in the western part of the Aleutian island arc showed that the seismic cycles here are shorter than in the eastern part of the arc. The authors revealed that major earthquakes, repeated in the same areas of the western part of the Aleutian subduction zone, differ both in magnitude and foci length. Taking into account the oblique subduction setting, the authors propose a keyboard model for the generation of major subduction-associated earthquakes as a mechanism potentially capable to explain the reduction in the seismic cycle duration and noticeable differences in the spatial extent and the foci localization of seismic events with similar magnitudes observed in the same segment of the western half of the Aleutian subduction zone.