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. The study of mantle convection pattern can improve our understanding of plate tectonics and geodynamics. The mantle convection pattern is affected by several factors, including the subducting slab geometry and slab-slab interactions. The tectonics in the Banda area is rendered particularly complex due to the subduction and interactions of multiple slabs. Hence, this region is an ideal natural laboratory to study the mantle flow pattern associated with slab-slab interactions. Here we invert both P and S wave arrival times of local earthquakes for 3-D anisotropic structure of the upper mantle beneath the Banda region. Our results show that in this curved subduction zone, the mantle convection pattern is different from that in normal subduction zones. Trench-parallel anisotropy is revealed beneath Banda, which reflects extruded material flow in the curved subduction zone. Our results provide new insight into subduction dynamics and mantle convection. The first P and S wave anisotropic tomography of the Banda subduction zone is obtainedTrench-parallel anisotropy along the Banda arc reflects lateral mantle flow caused by the highly curved Banda slabSemi-toroidal anisotropy around the northern edge of the Banda arc reflects extruded mantle flow from the arc

Automated summary

This study investigates the complex mantle convection pattern in a subduction zone with slab-slab interactions. By inverting a large amount of seismic wave arrival time data, the researchers uncover the 3-D velocity structures of the Banda subduction zone and reveal the presence of high-velocity and anisotropic zones associated with the subducting slab. The findings provide new insights into the dynamics of subduction zones and mantle convection.