Shear velocity structure across the Sumatran Forearc-Arc

Harmon, Nicholas and Henstock, Timothy and Tilmann, Frederik and Rietbrock, Andreas and Barton, Penny (2012) Shear velocity structure across the Sumatran Forearc-Arc. Geophysical Journal International, 189 (3). pp. 1306-1314. ISSN 1365-246X DOI 10.1111/j.1365-246X.2012.05446.x

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Abstract

We present a series of 1-D shear velocity models for the Sumatran Forearc and Arc derived from Rayleigh wave group dispersion in noise correlation functions from vertical and pressure records from an onshore–offshore seismic deployment. The 1-D models represent the crustal structure of the downgoing Indian Plate, the accretionary prism and the arc. There is a progression in shear velocity across the forearc to the arc associated with thickening of the accretionary prism and the development of an arc crust. The velocity structure inferred for the upper 20 km based on path averages between stations on the accretionary prism has velocities consistent with a thick sediment package in agreement with estimates of depth to the plate boundary determined from active source experiments. We also find low Indian Plate shear velocities, <4 km s−1 to 25 km depth beneath our station locations on the downgoing plate. These low seismic velocities are consistent with at least 14–24 per cent serpentinization of the oceanic crust and upper mantle of the downgoing plate. This high degree of serpentinization, may weaken the plate interface and explain the segmentation observed in the great Sumatran thrust earthquakes if the serpentinization is localized. The success of this study suggests that future onshore–offshore seismic deployments will be able to utilize this method.

Item Type: Article
Uncontrolled Keywords: 2012AREP; IA63;
Subjects: 02 - Geodynamics, Geophysics and Tectonics
Divisions: 02 - Geodynamics, Geophysics and Tectonics
Journal or Publication Title: Geophysical Journal International
Volume: 189
Page Range: pp. 1306-1314
Identification Number: 10.1111/j.1365-246X.2012.05446.x
Depositing User: Sarah Humbert
Date Deposited: 25 May 2012 10:17
Last Modified: 23 Jul 2013 10:04
URI: http://eprints.esc.cam.ac.uk/id/eprint/2527

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