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TitleContributions of poroelastic rebound and a weak volcanic arc to the postseismic deformation of the 2011 Tohoku earthquake
AuthorHu, Y; Burgmann, R; Freymueller, J T; Banerjee, P; Wang, K
SourceEarth, Planets and Space vol. 66, 106, 2014, 10 pages,
Alt SeriesEarth Sciences Sector, Contribution Series 20140087
Mediapaper; on-line; digital
File formatpdf
AreaTohoku; Sumatra; Japan; Japan
Lat/Long WENS 139.0000 144.0000 41.0000 36.0000
Subjectsgeophysics; tectonics; earthquakes; deformation; subduction zones; models; numerical simulation; weakened lower crust beneath the arc; viscoelastic postseismic deformation; finite element model; horizontal displacement
Illustrations3-D models; models; diagrams; graphs
ProgramWestern Canada Geohazards Project, Public Safety Geoscience
AbstractAbstract. A better understanding of fluid-related processes such as poroelastic rebound of the top crust and weakening of the lower crust beneath the volcanic arc helps better understand and correctly interpret the heterogeneity of postseismic deformation following great subduction zone earthquakes. The postseismic deformation following the 2011 Mw 9.0 Tohoku earthquake, recorded with unprecedented high resolution in space and time, provide a unique opportunity to study these ¿secondary-order¿ subduction zone processes. We use a three-dimensional viscoelastic finite element model to study the effects of the fluid-related processes on the postseismic deformation. The preferred poroelastic rebound (PE) model predicts a total of a few tens of centimeters uplift above the rupture zone and ~10 cm uplift near the eastern coast. PE produces up to ~10 cm of horizontal motions near the rupture areas and negligible horizontal displacements on land. Effects of a weak zone beneath the arc depend on its plan-view width and viscosity profile. Our preferred model of the weak sub-arc zone indicate that in the first two years after the 2011 earthquake, the weak zone contribute to the surface deformation at land up to 20 cm. The weak zone model helps eliminate the bias in the viscoelastic model of upper mantle relaxation and afterslip of the megathrust.
Summary(Plain Language Summary, not published)
The devastating M 9 Tohoku earthquake and its tsunami in 2011 caused not only tens of meters of crustal deformation during the earthquake but also meters of slower postseismic deformation since the earthquake. Understanding the many processes that affect the postseismic deformation helps us understand the mechanical properties of the crustal and mantle rocks that control earthquake cycles. This paper investigates two of these processes, poroelastic response of the crustal material and weak volcanic zone. The model results indicate that poroelasticity can be potentially important, and the volcanic arc weakened by partial melting of rocks can significantly affect postseismic deformation.