Abdullah Sanusi, Nabilah Husna
(2021)
Cross-gradient Joint Inversion Of 2d Resistivity And Seismic Refraction Methods.
Masters thesis, Universiti Sains Malaysia..
Abstract
Subsurface investigation commonly involved geophysical methods such as 2D resistivity and seismic refraction methods. Each methods are dependent on different physical parameters and has different sensitivity on subsurface structure. In this study, joint inversion with a cross-gradient constraint method was conducted to map and improved image characterization of lateral and vertical subsurface variation. The basic idea of this approach was to achieve a unified geological model which satisfies both data sets using cross-gradient constraint. This method was conducted on five synthetic models with lateral subsurface variation (Model 1, Model 2, and Model 3) and vertical subsurface variation (Model 4 and Model 5) as preliminary studies. Then, this method was applied to the study areas with lateral subsurface variation (Bunker USM, Tapak Konvo USM, and Guar Jentik) and vertical subsurface variation (Indah Kembara and Bukit Chondong). Particle size distribution (PSD) and X-ray diffraction (XRD) analysis were also conducted on soil and rock samples at Indah Kembara, Guar Jentik, and Bukit Chondong. Cross-gradient joint inversion of seismic model with lateral subsurface variation shows structural improvement of the anomaly. Meanwhile, separate inversion models with vertical subsurface variation already show structural similarities, hence no changes in both cross-gradient joint inversion models. Lateral subsurface variation such as Bunker USM and Tapak Konvo USM shows a structural improvement of the bunker (<40 Ωm, 1.4 - 1.6 km/s) and drain (< 50 Ωm, <0.9 km/s) in joint inversion of seismic models.
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