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

摘要

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 21 s are obtained using cross-correlation of six month's ambient seismic noise data recorded by these seismic stations. Joint inversion results show similar to 2 to 6 km thick subsurface low shear velocity (Vs similar to 1.3-2.5 km/s) layer followed by a 12-14 km thick layer of silicic material (average Vs similar to 3.5 km/s). The lower crust is mapped as an 8-12 km thick mafic layer with Vs similar to 4.0 km/s. Uppermost mantle shear wave velocity is similar to 4.55 km/s. The near-surface low-velocity layer is interpreted as the Andaman flysch sediments. The crustal thickness beneath the Andaman Island varies from similar to 24 km in the north to similar to 32 km 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. (C) 2016 Elsevier B.V. All rights reserved.