Tomographic Imaging of the Plate Geometry Beneath the Arunachal Himalaya and Burmese Subduction Zones

We present 3-D P and S-wave velocity perturbation maps of the upper-mantle beneath eastern Himalaya and Burmese subduction zones at 2 degrees x 2 degrees lateral resolution, using teleseismic travel-time tomography. Collated waveforms of 5,727 teleseismic earthquakes recorded at 273 seismic stations generated an accurate data set of 86,570 P-arrival and 85,227 S-arrival times using multichannel cross-correlation. Tomograms enabled imaging of the structural features down to 1,000 km depth. The subducting Indian lithospheric plate extends up to Bangong-Nujiang Suture Zone, overturns and descends steeply beyond 200 km below the Himalayan arc. A southward plunging detached slab can be traced beyond 600 km. Results reveal no evidence for the detachment of a S-E deflecting Indian lithospheric slab below the Burmese arc. The geometry of the slab mimics regional seismicity (up to 200 km) followed by a deeper aseismic zone related to petrological changes. No gaps are seen between the northward and eastward subducting Indian plate, hence confining the eastward escape of Tibetan-lithospheric material between the Eastern Himalayan Syntaxis and Sichuan Basin.