[J08-1] Imaging and interpreting lithospheric structures using seismic and geodetic approaches I

[J08-1-05] Waveform-based estimation of velocity heterogeneity for prestack imaging from multifold wide-aperture seismic data

^○Susumu Abe¹, Takao Nibe², Hiroshi Sato³, Tatsuya Ishiyama³ (1.Japan Petroleum Exploration Co., Ltd, Tokyo, Japan, 2.JGI, Inc., Tokyo, Japan, 3.Earthquake Research Institute, the University of Tokyo, Tokyo, Japan)

Deep seismic reflection profiling with rugged acquisition topography, crookedness of seismic lines has been imposed serious restrictions and compromises on both data processing and acquisition. In addition to complex subsurface structure, irregular distribution of shots, and large noise level of surface wave and back-scattered wave often result in deterioration of the data quality and poor reflection image in seismic profile. In recent years, the quest for increased precision and channel capacity of receiver system led to the combination of telemetry and autonomous recorders with the deployment of dense seismic array for deep seismic profiling in Japan. For deep seismic profiling with wide-aperture geometry, dense spatial sampling and low-frequency bandwidth, velocity structures estimated through turning-ray tomography (TRT) are restricted in resolution, since TRT depends on direct arrivals of seismic wave with the assumption of asymptotic ray theory. On the other hand, full waveform inversion (FWI) based on full wavefield modeling and inversion has an advantage to estimate high-resolution velocity heterogeneity. In our study, the hybrid velocity estimation of TRT, FWI and reflection velocity analysis by PSDM (Prestack Depth Migration) was applied to onshore-offshore integrated deep seismic data across Niigata basin, central Japan. The uncertainty of the tomography solutions was evaluated using a nonlinear Monte Carlo approach with randomized initial models, and the velocity structure of deep basin structure is constrained by subsequent forward reflection and refraction modeling. The combination of PSDM-driven velocity analysis and FWI was confirmed to have the potential imaging capabilities for improved prestack depth migration. Main features of basin development,　such as early Miocene normal faulting, associated with the formation of Japan Sea, and　shortening deformation since Pliocene, are well demonstrated on the final seismic sections.