Preprints
https://doi.org/10.5194/se-2021-40
https://doi.org/10.5194/se-2021-40

  14 Apr 2021

14 Apr 2021

Review status: this preprint is currently under review for the journal SE.

Reflection tomography by depth warping: A case study across the Java trench

Yueyang Xia1, Dirk Klaeschen1, Heidrun Kopp1,2, and Michael Schnabel3 Yueyang Xia et al.
  • 1Dynamics of the Ocean Floor, GEOMAR, Helmholtz Centre for Ocean Research Kiel, Kiel, 24148, Germany
  • 2Department of Geosciences, Kiel University, Kiel, 24118, Germany
  • 3Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Stilleweg 2, 30655 Hannover, Germany

Abstract. Accurate subsurface velocity models are crucial for geological interpretations based on seismic depth images. Seismic reflection tomography is an effective iterative method to update and refine a preliminary velocity model for depth imaging. Based on residual move-out analysis of reflectors in common image point gathers an update of the velocity is estimated by a ray-based tomography. To stabilize the tomography, several preconditioning strategies exist. Most critical is the estimation of the depth error to account for the residual move-out of the reflector in the common image point gathers. Because the depth errors for many closely spaced image gathers must be picked, manual picking is extremely time-consuming, human biased, and not reproducible. Data-driven picking algorithms based on coherence or semblance analysis are widely used for hyperbolic or linear events. However, for complex-shaped depth events, pure data-driven picking is difficult. To overcome this, the warping method named Non-Rigid Matching is used to estimate a depth error displacement field. Warping is used, e.g., to merge photographic images or to match two seismic images from time-lapse data. By calculating the displacements between an offset to its neighbouring offset in the common image point domain, a locally smooth-shaped displacement field is defined for each data sample. Depending on the complexity of the subsurface, sample tracking through the displacement field along predefined horizons or on a simple regular grid yields discrete depth error values for the tomography. The application to a multi-channel seismic line across the Sunda subduction zone offshore Lombok island, Indonesia, illustrates the approach and documents the advantages of the method to estimate a detailed velocity structure in a complex tectonic regime. By incorporating the warping scheme into the reflection tomography, we demonstrate an increase in the velocity resolution and precision by improving the data-driven accuracy of depth error picks with arbitrary shapes. This approach offers the possibility to use the full capacities of tomography and further leads to more accurate interpretations of complex geological structures.

Yueyang Xia et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on se-2021-40', Nathan Bangs, 11 May 2021
  • RC2: 'Comment on se-2021-40', César R. Ranero, 20 Jun 2021

Yueyang Xia et al.

Yueyang Xia et al.

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Short summary
Geological interpretations based on seismic depth images depend on an accurate subsurface velocity model. Reflection tomography is one method to iteratively update a velocity model based on depth error analysis. We used a warping method to estimate closely spaced data-driven depth error displacement fields. The application to a multichannel seismic line across the Sunda subduction zone illustrates the approach which leads to more accurate images of complex geological structures.