Teleseismic Traveltime Tomography of Northern Sumatra

We imaged the mantle structure beneath northern Sumatra by inverting high-quality seismic arrival time data and using a newly developed eikonal equation-based teleseismic tomography method. Traveltime differences between neighboring stations were reliably extracted by cross-correlating teleseismic waveforms, which were recorded by 26 stations from January 2009 to January 2018. Both P and S wave tomographic results show the oblique subduction of the Indo-Australian oceanic lithosphere beneath the Sunda plate. The maximum penetration depth of the subducted slab into the mantle varies roughly from 400km in the north to 800km in the south. The plunging fold of the subducted slab, which mimics the shape of the trench and the volcanic arc, has less curvature than that reported in the literature; additionally, our results suggest that the gentle slab fold can be traced to a depth of about 500km. Furthermore, a slab tear may exist beneath northern Sumatra. Plain Language Summary An eikonal equation-based software is developed for teleseismic traveltime tomography. A new subducting slab model for interpreting the slab morphology beneath northern Sumatra is obtained by inverting the high-quality seismic data and using the robust traveltime tomographic tool. The slab gentle folding, tearing, offset, and variation model may explain the major feature of the subducting slab beneath northern Sumatra. The complex slab morphology may be related to the lateral stress on the slab because of the oblique subduction and the movement of Sundaland margin.