Cecep Pratama, Takeo Ito, Ryohei Sasajima, Takao Tabei, Fumiaki Kimata, Endra Gunawan, Yusaku Ohta, Tadashi Yamashina, Nazli Ismail, Irwandi Nurdin, Didik Sugiyanto, Umar Muksin, Irwan Meilano
Postseismic motion in the middle-field (100–500 km from the epicenter) geodetic data resulting from the 2012 Indian Ocean earthquake exhibited rapid change during the two months following the rupture. This pattern probably indicates multiple postseismic deformation mechanisms and might have been controlled by transient rheology. Therefore, the relative contribution of transient rheology in the oceanic asthenosphere and afterslip in the oceanic lithosphere should be incorporated to explain short- and long-term transitional features of postseismic signals. In this study, using two years of post-earthquake geodetic data from northern Sumatra, a three-dimensional spherical-earth finite-element model was constructed based on a heterogeneous structure and incorporating transient rheology. A rheology model combined with stress-driven afterslip was estimated. Our best-fit model suggests an oceanic lithosphere thickness of 75 km with oceanic asthenosphere viscosity values of 1 × 1017 Pa s and 2 × 1018 Pa s for the Kelvin and Maxwell viscosity models, respectively. The model results indicate that horizontal landward motion and vertical uplift in northern Sumatra require viscoelastic relaxation of the oceanic asthenosphere coupled with afterslip in the lithosphere. The present study demonstrates that transient rheology is essential for reproducing the rapidly changing motion of postseismic deformation in the middle-field area. © 2017 Elsevier Ltd
Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan; International Institute of Seismology and Earthquake Engineering, Ibaraki, Japan; Department of Applied Science, Kochi University, Akebono-cho, Japan; Tono Research Institute of Earthquake Science, Mizunami, Japan; Graduate Research on Earthquake and Active Tectonics, Bandung Institute of Technology, Indonesia; Graduate School of Science, Tohoku University, Sendai, Japan; Department of Physics, Syiah Kuala University, Banda Aceh, Indonesia; Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Indonesia
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