Resolving the fine-scale velocity structure of continental hyperextension at the Deep Galicia Margin using full-waveform inversion

Davy, R G; Morgan, J V; Minshull, T A; Bayrakci, Gaye; Bull, J M; Klaeschen, D; Reston, T J; Sawyer, D S; Lymer, G; Cresswell, D. 2017 Resolving the fine-scale velocity structure of continental hyperextension at the Deep Galicia Margin using full-waveform inversion. Geophysical Journal International, 212 (1). 244-263. https://doi.org/10.1093/gji/ggx415

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Text This is a pre-copyedited, author-produced PDF of an article accepted for publication in Geophysical Journal International following peer review. The version of record R G Davy, J V Morgan, T A Minshull, G Bayrakci, J M Bull, D Klaeschen, T J Reston, D S Sawyer, G Lymer, D Cresswell, Resolving the fine-scale velocity structure of continental hyperextension at the Deep Galicia Margin using full-waveform inversion, Geophysical Journal International, Volume 212, Issue 1, January 2018, Pages 244–263, https://doi.org/10.1093/gji/ggx415 is available online at: https://academic.oup.com/gji/article/212/1/244/4331637#130611789. Davy_et_al_GJI_Resubmission.pdf Download (6MB) | Preview

Text This article has been accepted for publication in Geophysical Journal International ©: 2017 Davy, R.G. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. 4331637_redirectedFrom=fulltext Available under License Creative Commons Attribution 4.0. Download (152kB)

Abstract/Summary

Continental hyperextension during magma-poor rifting at the Deep Galicia Margin is characterized by a complex pattern of faulting, thin continental fault blocks and the serpentinization, with local exhumation, of mantle peridotites along the S-reflector, interpreted as a detachment surface. In order to understand fully the evolution of these features, it is important to image seismically the structure and to model the velocity structure to the greatest resolution possible. Traveltime tomography models have revealed the long-wavelength velocity structure of this hyperextended domain, but are often insufficient to match accurately the short-wavelength structure observed in reflection seismic imaging. Here, we demonstrate the application of 2-D time-domain acoustic full-waveform inversion (FWI) to deep-water seismic data collected at the Deep Galicia Margin, in order to attain a high-resolution velocity model of continental hyperextension. We have used several quality assurance procedures to assess the velocity model, including comparison of the observed and modeled waveforms, checkerboard tests, testing of parameter and inversion strategy and comparison with the migrated reflection image. Our final model exhibits an increase in the resolution of subsurface velocities, with particular improvement observed in the westernmost continental fault blocks, with a clear rotation of the velocity field to match steeply dipping reflectors. Across the S-reflector, there is a sharpening in the velocity contrast, with lower velocities beneath S indicative of preferential mantle serpentinization. This study supports the hypothesis that normal faulting acts to hydrate the upper-mantle peridotite, observed as a systematic decrease in seismic velocities, consistent with increased serpentinization. Our results confirm the feasibility of applying the FWI method to sparse, deep-water crustal data sets.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1093/gji/ggx415
ISSN:	0956-540X
Date made live:	26 Mar 2019 11:08 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/522656

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