Continental like crust beneath the Andaman Island through joint inversion of receiver function and surface wave from ambient seismic noise

Abstract

We study shear wave velocity structure of the crust beneath the Andaman Island through joint inversion of the teleseismic receiver function and Rayleigh wave group velocity measurements from 10 broadband seismographs over the Island. The group velocities in the periods from 5 to 21s are obtained using cross-correlation of six month's ambient seismic noise data recorded by these seismic stations. Joint inversion results show ~2 to 6km thick subsurface low shear velocity (Vs ~1.3–2.5km/s) layer followed by a 12–14km thick layer of silicic material (average Vs ~3.5km/s). The lower crust is mapped as an 8–12km thick mafic layer with Vs ~4.0km/s. Uppermost mantle shear wave velocity is ~4.55km/s. The near-surface low-velocity layer is interpreted as the Andaman flysch sediments. The crustal thickness beneath the Andaman Island varies from ~24km in the north to ~32km in the south. The shear wave velocity-depth results show that the crustal structure beneath the Andaman Island is akin to continental crust, possibly the Burma continental crust. The subducting Indian plate may lie down below this overriding plate.