Abstract

Recent advances in full-3D seismic tomography (F3DT), in which the starting model and the inverted model perturbations are 3D in space and the sensitivity (Fréchet) kernels are computed using purely numerical solutions of 3D (visco) elastodynamic equations, have opened up new possibilities for imaging the structures of the near surface where mechanical properties of materials play important roles in various geotechnical engineering applications. In this study, we have successfully applied F3DT to image the near-surface structure under a granitic ridge in the Blair Wallis watershed, southeastern Wyoming. The seismic data used in our tomography consist of both 2D active-source seismic refraction data and 3D ambient-noise Green’s functions obtained from a minimally invasive “large-N” seismic survey using a square array of 400 autonomous geophones. Lateral variations of our 3D velocity model show strong correlations with surface topography. Depth variations of our velocity model may give clues about the depth interval within which chemical weathering plays a significant role. With the calibration of borehole casing depths and saprolite refusal depths, our F3DT technique can be a highly effective tool for investigating the structure of the near surface.

Citation

WANG W., CHEN P., LEE EJ., MU D. (2019): Full-3D Seismic Tomography for Structure of the Critical Zone. Chapter in Earthquake and Disaster Risk: Decade Retrospective of the Wenchuan Earthquake, 1st Ed. Y.G. Lee (Ed.) Higher Education Press & Springer Nature Singapore. DOI: 10.1007/978-981-13-8015-0_8