Multiple Slabs and Complex Mantle Flows in the Molucca Sea Subduction Zone

Abstract

The Molucca Sea subduction zone is unique for its active divergent double-subducted slab located in the north of the Java and Banda subduction zones. The spatial proximity of these subduction zones would cause a complex mantle flow field. To clarify the mantle dynamics, here we present P-wave tilting-axis anisotropic tomography obtained by inverting a large number of local and teleseismic travel-time data recorded at 254 seismic stations in eastern Southeast Asia. Our results suggest that the mantle structure and dynamics of the western Molucca Sea subduction zone may be remotely controlled by the Java and Banda subduction zones. Mantle convection in the big mantle wedge west of the Molucca Sea subduction zone is possibly influenced by east-west mantle flow associated with compression of the Indo-Australian slab as well as north-south mantle flow related to rollback of the Indo-Australian slab. In contrast, the eastern Molucca Sea subduction zone is virtually unaffected by other subduction zones, probably due to the ongoing slab subduction there.