09:45 〜 10:00
[SSS04-04] The application of full waveform inversion in marine seismology: from industry to tectonics
★Invited Papers
キーワード：seismic, full waveform inversion, subduction zone
Full waveform inversion (FWI) has become an important method to extract information from the subsurface in the oil and gas industry. It involves iteratively minimizing a misfit function between observed and synthetically calculated data. The FWI has been most successful in inverting first arrival refracted or wide-angle reflection data, providing information on short to medium wavelength information, and filling the gap between the long wavelength information provided by travel time tomography and the short wavelength information from pre-critical seismic reflection data. Therefore, it has been mainly used in shallow waters where refraction arrivals are observed at short offsets. However, in the field of tectonics, we always need to deal with deep waters and complex seafloor environments, such as subduction zones. Therefore, longer streamer and sparsely spaced ocean bottom seismometer (OBS) data could be helpful to acquire refractions to investigate the deep structures through the complex topography. Here I show the application of FWI to both streamer data and OBS data acquired in two subduction zones, respectively. The first case is by using a 15-km-long offset streamer data acquired offshore Sumatra. I applied downward continuation to the streamer data to improve S/N ratio and boost the refraction arrivals, and then performed FWI on the preprocessed data. The second case study target at the recent densely deployed OBS data (1 km apart from each) acquired in the Nankai Trough, a combination of ray tracing tomography and FWI has been applied, and reconstructs the detailed subsurface velocity structure. Both cases suggest that the FWI method is much more advanced than the traditional traveltime tomography, and it can provide much higher resolution quantitative imaging of the subsurface.