Seismotectonic Deformations of the Kuril Island Arc during Different Phases of the Seismic Cycle: The Simushir Earthquakes

摘要

Multiyear satellite geodetic measurements along the Kuril island arc provided data for studying the condition of the Benioff seismic zone and the occurrence of various deformation mechanisms that are responsible for surface displacements. Factors have been determined whose combination can explain the diverse character of observed movements: space-time variations in interplate sliding, viscoelastic postseismic relaxation in the asthenosphere, stationary backward mantle flow, the keyboard structure of the frontal part of the subduction zone. The stationary displacement components have been detected against the background of transient processes. These components can be associated with interplate coupling and sublithospheric currents and they can be employed in order to characterize the interseismic condition of various parts along the Kuril isalnd arc. In particular, the special character of seismicity in the Middle Kuril area, which consists in long intervals of seismic quiescence interrupted by large double earthquakes, can be caused by a zone of hypothetical transition from strong interplate coupling in the southwest to poor coupling combined with a backward sublithospheric current in the northeast.