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Solid Earth An interactive open-access journal of the European Geosciences Union
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Discussion papers
https://doi.org/10.5194/se-2019-33
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/se-2019-33
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 01 Mar 2019

Research article | 01 Mar 2019

Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Solid Earth (SE) and is expected to appear here in due course.

Crustal-scale depth imaging via joint FWI of OBS data and PSDM of MCS data: a case study from the eastern Nankai Trough

Andrzej Górszczyk1,2, Stephane Operto3, Laure Schenini3, and Yasuhiro Yamada4 Andrzej Górszczyk et al.
  • 1Institute of Geophysics, Polish Academy of Sciences, ul. Ks. Janusza 64, 01-452 Warsaw, Poland
  • 2Univ. Grenoble Alpes, ISTerre, 38000 Grenoble, France
  • 3Université Cote d’Azur, CNRS, OCA, Géoazur, Valbonne, France, 250 Rue Albert Einstein, 06560 Valbonne
  • 4R&D Center for Ocean Drilling Science, JAMSTEC, 3173-25 Showa-machi, Yokohama, 236-0001, Japan

Abstract. Imaging via Pre-Stack Depth Migration (PSDM) from reflection towed-streamer Multi-Channel Seismic (MCS) data at the scale of the whole crust is inherently difficult. This mainly results because the depth-penetration of the seismic wavefield is controlled, firstly (i) by the acquisition design, like streamer length and air-gun source configuration, and secondly (ii) by the complexity of the crustal structure. Indeed, the limited length of the streamer makes the estimation of velocities from deep targets challenging due to the velocity-depth ambiguity. The problem is even more pronounced when processing 2D seismic data, due to the lack of multi-azimuthal coverage. Therefore, in order to broaden our knowledge about the deep crust using seismic methods, one shall target the development of specific imaging workflows integrating different seismic data. Here we propose the combination of velocity model-building using (i) first-arrival traveltime tomography (FAT) and full-waveform inversion (FWI) of wide-angle/long-offset data collected by stationary Ocean Bottom Seismometers (OBS) and (ii) PSDM of short-spread towed-streamer MCS data for reflectivity imaging, using the former velocity model as background model. We present an application of such workflow to seismic data collected by Japan Agency for Marine-Earth Science and Technology (JAMSTEC) and Institut Français de Recherche pour l’Exploitation de la Mer (IFREMER) in the eastern Nankai Trough (Tokai area) during the 2000/2001 SFJ experiment. We show that the FWI model, although derived from OBS data, provides yet an acceptable background velocity field for the PSDM of the MCS data. Furthermore, from the initial PSDM, we first refine the FWI background velocity model by minimizing the residual moveouts (RMO) picked in the prestack migrated volume through slope tomography (ST), from which we generate a better focused migrated image. Such integration of different seismic data sets and leading-edge imaging techniques led to optimal imaging results at different resolution levels. That is, the large-to-intermediate scale crustal units identified in the high-resolution FWI velocity model extensively complement the short-scale reflectivity inferred from the MCS data to better constrain the structural factors controlling the geodynamics of the Nankai Trough area.

Andrzej Górszczyk et al.
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Interactive discussion
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Andrzej Górszczyk et al.
Andrzej Górszczyk et al.
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Short summary
In order to broaden our knowledge about the deep lithosphere using seismic methods, one shall target the development of leading-edge imaging workflows integrating different types of data. Here we exploit the complementary information carried by the seismic wavefields which are fundamentally different in terms of acquisition setting. We cast these information into the processing workflow and build the detailed model of the subduction zone which is subject to further geological interpretation.
In order to broaden our knowledge about the deep lithosphere using seismic methods, one shall...
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