[S-SS07] Seismic wave propagation: Theory and Application

[SSS07-09] Improvement of accuracy of subsurface structure estimation through extraction of various wavefield information

*Susumu Abe¹, Masafumi KATOU¹, Hiroshi Sato², Tatsuya Ishiyama², Hideo Saito¹ (1.JGI, Inc., 2.ERI, Univ. of Tokyo)

Keywords:Subsurface Imaging, Wavefield estimation, Full waveform inversion

In the visualization of subsurface structures using seismic data, it is important to construct an integrated three-dimensional model of subsurface structure and physical- mechanical properties as a digital twin by improving the resolution and diversifying evaluation indices, aiming at understanding structural morphology, estimating physical properties information including fluid flow, and understanding mechanical properties. Using such a digital twin of subsurface structures, it will be possible to understand and predict the time history of fluid flow in the subsurface and verify it using monitoring data, accelerate data processing and analysis by applying advanced AI and machine learning techniques. In recent years, various approaches have been proposed to improve the acquisition of seismic data, which is a prerequisite for the construction of a sophisticated digital twin. The first is the increase in the dense special sampling for the purpose of suppressing spatial aliasing, achieving uniform sampling in the common receiver-seismic-offset region, suppressing the "acquisition footprint," and dramatically increasing the number of effective merges. The second point of view is broadband seismic acquisition to extract deep reflected waves through expansion of low-frequency propagation energy and to improve time resolution by securing effective energy in the high-frequency effective region. The third point of view is to reduce the cost of large-scale exploration in accordance with the simultaneous acquisition of refracted, reflected, and wide-angle reflected waves, assuming a variety of seismic sources and variable seismic spacing. Through the advancement of these data acquisition techniques, multi-scale exploration from shallow to deep areas has been realized, and the sophistication of velocity structure estimation, mainly FWI analysis, has progressed to the stage where individual imaging using various wavefields such as reflected waves, refracted waves, scattered waves, surface-related multiples and surface waves, or FWM imaging using the total wavefield is possible. In this study, we present the basic concept and application examples of subsurface structure modeling through the extraction of various wavefield information using deep structural exploration data and synthetic waveform data in Japan.