Departmental Bulletin Paper Basic Numerical Simulation of Large-Scale Plume Activity Due to the Circum-Pacific Lithosphere Subduction and Implications for the Elementary Process Associated with the Static-Layered Terrestrial Mantle

EGUCHI, Takao  ,  ISHIDA, Mizuho  ,  MATSUBARA, Kiyoshi  ,  MURAKOSHI, Takumi  ,  IWASE, Yasuyuki

Vol.57 ( No.1 )  , pp.1 - 10 , 2017-09 , 防衛大学校
To unveil the global dynamics of long-term lithosphere subduction along the circum-Pacific Oceanand relationship with large-scale mantle plume activity, we conducted 3-D spherical numericalsimulations using a newly developed program. This program is based on the finite difference methodwith the Boussinesq (incompressible) approximation and temperature-dependent viscosity. Toobtain a higher precision time integral, we adopted the Newton method. In addition, thepreconditioned ‘Bi-CGSTAB’ (Bi-Conjugate Gradient Stabilized) method was incorporated to solvethe Jacobian matrix of five finite difference equations for the velocity vector, pressure, andtemperature. The preconditions used were matrix-matrix multiplication and incomplete LUfactorization. We subsequently modeled circum-Pacific lithosphere subduction using the initialcondition of a cool ring, at the base of the upper mantle along the equatorial great circle, imposed onthe horizontally uniform temperature field with thermal boundary layers. The results indicatedmajor upwellings at latitudes ± 30~40° as a response function. Secondary rising systems at bothpolar regions were clear. Our result numerically manifests part of the Green function-likeelementary processes of large-scale passive flows within the static layered terrestrial mantle.

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