[S-SS08] Crustal Structure

[SSS08-P06] Contribution to the Delineation of Crustal Structure by Advances in Seismic Exploration Techniques and Expectations for the Future

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

Keywords:Seismic Reflection Exploration, Deep Crustal Structure, Full Waveform Inversion

For seismic exploration of crustal structure 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. Where volcanic rocks are distributed hierarchically, it is more difficult to extract weak reflected waves and estimate their velocity due to the attenuation of seismic energy and the decrease in SN by surface backscattering. 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 analysis, the convergence, stability, and resolution of the estimated velocity profile were assured by expanding the effective low-frequency content. 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. In this study, we examine the results of deep reflection wave extraction and velocity estimation using crustal exploration data in Japan, and look forward to the future of crustal structure delineation through the development of exploration and monitoring technologies based on fiber-optic sensing.