[S-SS08] Crustal Structure

[SSS08-01] Contribution to the Imaging of Heterogeneous Geological Structures by Recent Advances in Seismic Reflection Exploration

*Susumu Abe¹, Hidehiko Shimizu², Hideo Saito¹, Hiroshi Sato³, Tatsuya Ishiyama³ (1.JGI, Inc., 2.JOGMEC, 3.ERI, Univ. of Tokyo)

Keywords:Seismic Reflection Exploration, Broadband Seismic Acquisition, Full Waveform Inversion

For seismic exploration in difficult terrain and complex geology in Japan, it has been a longstanding issue to optimize the data acquisition specifications and to improve the data processing techniques for heterogeneous velocity estimation and subsurface structure imaging to extract weak reflection signals in ambient and coherent noise environment. In particular, the resolution of seismic reflection profile will be degraded due to velocity estimation errors for faults and folded structures that have significant short wavelength structural inhomogeneity relative to the effective aperture of data acquisition. In addition, acquisition footprints due to irregular acquisition geometry and heterogeneity of seismic source-receiver response are also major inhibiting factors for seismic imaging. In our study, the recent advances in reflection seismology are comprehensively introduced to resolve the problem of visualization of heterogeneous subsurface structures. First, the broadband technology for seismic source and receiver systems improves the time-domain resolution and effective extraction of deep reflections through the expansion of low-frequency energy. In FWI(full waveform inversion) analysis, the convergence, stability, and resolution of the estimated velocity profile were assured by expanding the effective low-frequency content below 5 Hz. Second, as a multi-mode seismic survey technology, The combination of telemetry and WiFi recording system provides the deployment of long survey line across the area of land-marine transition zones with dense seismic array. As a result, the simultaneous acquisition of refracted, reflected and wide-angle reflected wave has realized accurate velocity estimation and advanced structural imaging. Third, the dense receiver-source spacing contributes to the suppression of spatial aliasing, the realization of uniform sampling, the elimination of acquisition footprint and the significant increase of the effective number of stacking folds, as well as the suppression of various coherent noises and the improvement of the accuracy of high-precision imaging and normalization processes. In our study, we evaluated the relation between reconstructed velocity heterogeneity and the resolution of reflection patterns using typical multi-scale deep reflection data acquired in the northeast Japan.