Arc-continent collision in action: insights from passive seismic imaging in Banda arc and Australia continental margin
Banda arc-Australian continental collision zone in Southeast Asia is one of the least well-understood geological regions on Earth, yet it offers a truly remarkable location for resolving key puzzles of plate tectonics. In Banda region, the recent collision between the Australian continental margin and an active volcanic arc effectively captures the initiation of continental mountain building and the cessation of island arc volcanism, offering a rare glimpse into the tectonic transition from subduction to arc-continent collision. To understand how this transition evolves, a passive seismic experiment composed of 30 broadband seismometers was carried out across the archipelago of Eastern Indonesia and Timor-Leste, recording nearly five years of data (2014-2019). In this talk, I will present the recent imaging results from this experiment, integrating ambient noise tomography, teleseismic surface wave tomography, receiver functions, coda auto-correlation, and shear wave splitting. Combined with geological and geochemical data, these seismic results reveal 1) the subducted/underthrusted Australian continental margin at lithospheric depths; 2) tectonic fabrics and crustal seismicity related to the orogenesis and magmatic systems; 3) structural heterogeneities inherited from the incoming plate; 4) an enigmatic boundary along the volcanic arc transitional zone. Altogether, we propose that the inherited structures of the rifted margin within the incoming plate, formed during the breakup of East Gondwana in the Jurassic, might play a significant role in the tectonic transition from subduction to arc-continent collision.
