||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, TakumiIWASE, Yasuyuki
MEMOIRS OF THE NATIONAL DEFENSE ACADEMY
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.