A combined imaging and modelling approach to understand magmatic systems across the SE Asia-Australia collision zone

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The zone of collision between the southern region of the Eurasian plate and Australia is a complex aggregate of Gondwana-derived terranes, subducting plates, and a colliding lithospheric block. Recently we have achieved significant resolution on the deep regional subduction for both P- and S-waves, especially across the Banda Sea. Seismic arrays recently deployed across the region now allow to increase resolution across the entire collision zone. Still, attenuation remains an important obstacle for a reliable lithospheric-scale, full-waveform-inversion of the area. Attenuation tomography can both fill this gap and offer improved sensitivity and illumination on lithospheric processes, especially those leading to magmatism. The first objective of this proposal is to image the lithospheric-scale attenuation structures leading to volcanism across the SE Asia – Australia collision zone, providing (1) a regional-scale benchmark to improve full-waveform imaging at regional scale and (2) improved imaging of the lithospheric structures connecting mantle structures to magmatic centres. To do so, the project will adapt an existent machine-learning framework for velocity tomography to waveform analysis, and will join 3D direct-wave-attenuation imaging with crustal absorption and scattering mapping. The end-results will be used together with existent tomographic models and available data from partners for the second objective: performing regional-scale visco(elasto)plastic modelling for (1) the entire collision zone and (2) the magmatic systems feeding Agung volcano, once combined to an adjoint-based inversion scheme. Using the derived high-resolution and mechanically-consistent structural models, the final deliverables will allow a better quantitative evaluation of the mechanisms in play in the zone of collision, giving insight into magma and fluid migration from subduction to surface.