Geophysical processes and biosphere: article

Аnnotation: On December 26, 2004, one of the three strongest earthquakes in the world history of seismic observations occurred in the Indian Ocean near the northwest coast of Sumatra, Indonesia, at a depth of 30 km - the Great Andaman-Sumatra earthquake with a magnitude of Mw = 9.2. The rupture on the surface with this earthquake reached 1200-1600 km, during which a right-sided rock shift occurred 15 m along the subduction zone of the Indian lithospheric plate under the Sunda arc in the west of Southeast Asia (Melanesia) and the Burmese plate in the north (included in the composition of a larger Eurasian plate). It was assumed that such a strong seismic event should manifest itself in changes in the long-term type of seismotectonic deformation in its vicinity. The search for these changes was the content of this study. On the basis of sets of focal mechanisms of earthquakes with Mw ≥ 5, published in the ISC catalog, estimates of the type of seismotectonic deformation (STD) in the space-time vicinity of this earthquake were made. Long-term assessments of the STD type are in satisfactory agreement with modern concepts of the nature of collision of lithospheric plates in the western part of the Sunda arc and confirm the geological notions of near horizontal compression (shortening) across the strike of the arc in the immediate vicinity of the epicenter of the earthquake. At the same time, noticeable variations of the STD type are established in comparison with long-term estimates at different time intervals relative to the time of the Sumatran earthquake. These variations can be explained by changes in the kinematics of deformation at different stages of deformation process development in the spatio-temporal vicinity of this strongest seismic catastrophe. At the same time, in the control sample to the south of the considered territory, where the rupture did not spread during the seismic catastrophe under consideration, the type of seismotectonic deformation did not undergo any appreciable temporary changes throughout the time interval examined.