Postseismic evolution of great earthquake source zones
Category: 16-2UDC 550.3:551.24.02
I.S. Vladimirova(1), G.M. Steblov(1,2)
(1) Geophysical Survey RAS, Obninsk, Kaluga reg., Russia
(2) Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia
Abstract. In the course of active satellite geodesy observations in two recent decades post-seismic deformations have been revealed for the majority of the strongest earthquakes in various seismically active regions. Among these are earthquakes that occurred in the Japan-Kuril-Kamchatka island arc (Kronotsky 1997, Simushir 2006–2007, Tohoku 2011), Sumatra-Andaman subduction zone (2004, 2007), Chilean subduction zone (2010). The typical common feature of all those events is the similar mechanism of the smooth interplate subduction thrust. The long-term post-seismic displacements revealed for all the above events represent one of the most discussible kind of observable surface deformations. Their explanation is complicated due to both the ambiguity of possible mechanisms and the necessity to analyze the rheology of the upper mantle. When modeling multiyear viscoelastic processes it is also necessary to consider the possible aseismic afterslip motion along the seismic fault in the first months after an earthquake. At the same time the long-term time series of the post-seismic motions observations contain enough information on the possible effective coseismic slip distribution, which allows to evaluate it and to use it to predict the future intensity of these motions, in particular, their attenuation time.
Study and simulation of post-seismic processes in similar areas are necessary for acquiring information on their deep structure and for adequate comparison of the deformation potential with the seismic energy released during an earthquake. Without this it is impossible to predict the intensity of the further accumulation of the deformation potential because the models of elastic deformation before the earthquake are not applicable in the subsequent period up to 2–3 decades, during which the observed displacement of the earth surface substantially alter their direction and magnitude.
Keywords: subduction, postseismic deformation, viscoelastic relaxation, rheology of the mantle.
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