[S-SS08] Crustal Structure

[SSS08-06] Understanding earthquake source faults and active fault systems through advances in heterogeneous structure imaging technology

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

Keywords:Earthquake source fault and active fault System, Imaging of heterogeneous structure, Full waveform inversion

Since the early 2000s, deep crustal structure surveys have been actively conducted to understand the detailed geometry of slabs subducting beneath the Japanese islands, the basic structure of sedimentary basins in plate convergence zones, and the location and geometry of onshore earthquake source faults. The importance of imaging earthquake source fault systems has been emphasized. Advances in seismic exploration technology have provided a better understanding of the branching characteristics of source-active fault systems, as well as the heterogeneous structure and segmentation of active faults. This has also contributed to the evaluation of variable topography and the construction of fault models through high-resolution shallow seismic imaging, as well as the visualization of three-dimensional fault structures through HR3D seismic exploration. In recent years, advances in seismic data acquisition have been realized through the use of broadband technology to extract deep reflected waves and improve time resolution, the suppression of spatial aliasing, uniform sampling in the common receiver-source offset domain, and dense spatial sampling of source and receiver. Furthermore, the combination of various seismic sources and autonomous seismic receiver systems enables the simultaneous acquisition of different wavefields. With the development of data acquisition technology, multi-scale exploration from shallow to deep has become a reality, and individual imaging using various wavefields, such as reflected waves, refracted waves, scattered waves, multiple reflected waves passing through the ground surface, and surface waves, is proceeding. In addition, secondary wavefield analysis derived from the application of seismic interferometry and integrated imaging through full waveform migration analysis using all wavefields have gradually become practical in recent years. In this study, we present case studies related to the advancement of heterogeneous velocity-structure imaging using deep structure exploration data and synthetic waveform data targeting source-active fault systems, and we also review the future of fault modeling through the development of seismic exploration technology.