Deep crustal reflection imaging by applying seismic interferometry to common receiver gathers of marine wide-angle seismic data

Abstract

We applied the seismic interferometry to marine wideangle data in order to obtain a deep crustal reflection profile without spatial imaging gaps due to sparse deployment of ocean bottom seismographs (OBSs). While the airgun-OBS wide-angle survey is useful to acquire reflections or refractions from deep crustal structures, it is difficult to obtain a spatially continuous reflection image by a conventional method because of the restricted horizontal coverage with primary reflections. In our study, by applying the seismic interferometry to the OBS common receiver gathers, we redatum the surface-related multiple reflections to the primary reflections of a virtual seismic survey data that all sources and receivers are located at all original airgun shot positions. As a result of the redatuming, the reflection imaging area is expanded, and the imaging gaps between OBSs are fully filled on a final reflection profile. In this paper, we show a concept of the interferometric redatuming, and an example of a marine wide-angle data on a 175 km-long survey line in the Nankai trough. The OBS wide-angle reflection data usually contains lower frequency energy than the high resolution multi-channel streamer survey (MCS), and important information from deep crustal structures in a long offset range. Although the spatial resolution of the OBS interferometric imaging is lower than the MCS survey, the final profile clearly shows the crustal structures in the plate subduction zone. In the discussion, we show the importance of the OBS spacing in a survey and the offset range between airgun shot and OBS for the interferometric redatuming and the gapless imaging of the crustal structures.