Fate of Forearc Lithosphere at Arc-Continent Collision Zones: Evidence From Local Earthquake Tomography of the Sunda-Banda Arc Transition, Indonesia

P. Supendi , A. D. Nugraha , S. Widiyantoro , C. I. Abdullah , N. Rawlinson , P. R. Cummins , C. W. Harris (1) , N. Roosmawati , M. S. Miller

1 EOST - Ecole et Observatoire des Sciences de la Terre

A new 3-D seismic P wave velocity model of the Sunda-Banda Arc Transition from local earthquake tomography reveals (i) northward subduction of oceanic lithosphere, associated with the convergence of Australia and Sundaland, as a high-velocity zone extending down to ~200 km depth; (ii) two distinct low-velocity zones, one immediately above the slab, which is likely a zone of partial melt, and one in the 0-40 km depth range, which is probably a magma chamber associated with active volcanoes above; and (iii) a northerly dipping high-velocity zone that bisects the two low-velocity anomalies, which we interpret as an underthrust forearc sliver of continental origin. Based on He³/He⁴ measurements from volcanic outflows, it is possible that the magma supply is contaminated by interaction with this forearc sliver as it ascends from the melt region below.

Keywords: tomography; subduction; collision; earthquakes; Indonesia

Domains: Sciences of the Universe [physics]; Sciences of the Universe [physics]; Earth Sciences

P. Supendi, A. D. Nugraha, S. Widiyantoro, C. I. Abdullah, N. Rawlinson, et al.. Fate of Forearc Lithosphere at Arc-Continent Collision Zones: Evidence From Local Earthquake Tomography of the Sunda-Banda Arc Transition, Indonesia. Geophysical Research Letters, 2020, 47, ⟨10.1029/2019GL086472⟩. ⟨insu-03707761⟩