Geologic and Structural Evolution of the NE Lau Basin, Tonga: Morphotectonic Analysis and Classification of Structures Using Shallow Seismicity

The transition from subduction to transform motion along horizontal terminations of trenches is associated with tearing the subducting slab and strike-slip tectonics in overriding plate. One prominent example northern Tonga zone, where abundant faulting NE Lau back-arc basin plate boundary asymmetric rollback. Here, we address fundamental question: how does this subduction-transform influence structural magmatic evolution region? To answer this, undertake first comprehensive study geology geodynamics region through analyses morphotectonics (remote-predictive geologic mapping) fault kinematics interpreted ship-based multibeam bathymetry Centroid-Moment Tensor data. Our results highlight two notable features Basin: 1) occurrence widely distributed off-axis volcanism, contrast typical ridge-centered 2) dominated by shallow-crustal strike slip-faulting (rather than normal faulting) extending over ?120 km boundary. orientations these faults are consistent reactivation earlier-formed a sinistral megashear zone. Notably, distinct sets Riedel megashears identified, indicating recent counter-clockwise rotation part stress field closest arc. Importantly, structures identified directly control development complex volcanic-compositional provinces, which characterized variably-oriented spreading centers, volcanic ridges, extensive lava flows, point-source rear-arc volcanoes. This adds our understanding modern backarc systems, including association between motions siting style seafloor volcanism.