Shear Velocity Structure Across the Indo-Burman Accretionary Margin from Ambient-Noise and Teleseismic Rayleigh Waves
Abstract
The ongoing collection of broadband seismic data across the Indo-Burman Subduction Zone provides an opportunity to investigate the subsurface velocity structure across an endmember system for sedimentary accretion. The Indo-Burman Subduction Zone is an active subaerial accretionary system with its blind deformation blanketed by the massive Ganges-Brahmaputra Delta (GBD), which extends > 300 km in length and reaches up to 19 km in thickness. Recent GPS results indicate that this highly oblique boundary is locked, though the unique subduction system and the extent of sediment subduction there have not yet been extensively studied.
As part of a larger multidisciplinary transect, the BIMA (Bangladesh-India-Myanmar Array) seismic experiment of the Tripartite Project includes the deployment of twenty-eight broadband seismometers in Bangladesh and thirty-one in Myanmar installed in February and November 2018, respectively. We utilize surface-wave data from two types of observations: (1) the phase velocities of interstation Rayleigh wavefields produced via cross-correlation of ambient seismic noise; and (2) the relative phase variations of Rayleigh waves from regional and teleseismic earthquakes propagating across the array. Phase velocities of vertical-component ambient-noise cross-correlations are calculated using a spectral fitting technique, while those from earthquake sources are calculated from phase and amplitude measurements following a multi-channel cross-correlation algorithm. Together, they can be combined to invert for the shear-velocity structure of the sediments, crust and uppermost mantle, providing critical constraints on the sediment and fluid distribution, and possibly the downgoing plate.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.T21F0387C
- Keywords:
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- 8120 Dynamics of lithosphere and mantle: general;
- TECTONOPHYSICS;
- 8121 Dynamics: convection currents;
- and mantle plumes;
- TECTONOPHYSICS;
- 8170 Subduction zone processes;
- TECTONOPHYSICS;
- 8180 Tomography;
- TECTONOPHYSICS