P and S Wave Anisotropic Tomography of the Banda Subduction Zone

In subduction zones with slab-slab interactions, the pattern of mantle convection is very complex and still unclear. In this study, we jointly invert a large number of P and S wave arrival time data of local earthquakes for 3-D isotropic and anisotropic velocity structures of the Banda subduction zone. Along the curved Banda arc, the subducting Indo-Australian slab is detected clearly as a high-velocity zone, and its azimuthal anisotropy changes along the arc strike, representing fossil anisotropy within the slab and modified anisotropy by the subduction processes. Around the northern edge of the Banda slab, a semi-toroidal pattern of anisotropy appears in low-velocity anomalies, representing mantle flow extruded from the Banda arc and escaped from a gap of the Banda-Molucca slab toward the northeast. Our 3-D anisotropic tomography uncovers the mantle convection pattern induced by the slab-slab interactions, shedding new light on the complex dynamical processes in this curved subduction zone.