Seismic Imaging of the Subducted Australian Continental Margin Beneath Timor and the Banda Arc Collision Zone

Abstract

Detailed crustal and uppermost mantle structure is imaged for the first time utilizing ∼4 years of broadband seismic data newly collected in the Timor-Leste and Nusa Tenggara Timor region of Indonesia. We apply three techniques, ambient noise tomography, teleseismic P wave receiver function, and coda autocorrelation, to resolve a 3D Vs model and Moho structure. Our tomographic images show low-velocity anomalies (<30 km) beneath Timor related to underthrusted Gondwana sequence from the Australian plate, which are vertically offset by the high-velocity backstop of the Banda forearc terrane. The structure progressively changes along strike, reflecting different collisional stages developed as a result of the oblique convergence. At greater depth, we detect seismically fast lithospheric mantle (>30 km) and the arc-ward dipping Moho beneath Timor, both interpreted to be from the Australian plate. Our findings provide direct structural evidence of the Australian continental margin at lithospheric depths beneath the Banda Arc collisional zone.