Date of Award

2020

Document Type

Open Access Master's Thesis

Degree Name

Master of Science in Geophysics (MS)

Administrative Home Department

Department of Geological and Mining Engineering and Sciences

Advisor 1

Roohollah Askari

Committee Member 1

Gregory P. Waite

Committee Member 2

Nathan D. Manser

Abstract

Ambient noise seismic interferometry (ANSI) is a method that uses passive noise created by unknown sources such as local or teleseismic earthquakes, waves, wind, fracturing and fault movement in a reservoir to obtain an image of subsurface. ANSI has been used in some various disciplines, including earthquake engineering, time-lapse monitoring, borehole seismology and seismic exploration for years. Compared to conventional active seismic surveys, it is advantageous in terms of cost-efficiency as no active source such dynamite or vibroseis is used. Although many promising results have been obtained from surface wave ANSI, body wave ANSI is still challenging. Such a challenge might stem from the inherent lower amplitude of the body waves compared to the surface waves. To improve body ANSI, many methodologies based on seismic data processing and acquisition have been proposed. The main objective of this study is to answer this question whether the zero-offset vertical seismic profiling (VSP) can provide additional information of subsurface in ANSI surveys if it is included along the conventional surface seismic data acquisition. Thus, I evaluate two different data acquisition techniques, surface seismic and zero-offset VSP data acquisitions for recovering body wave data from ANSI. To assess each of these data acquisition approaches on ANSI results, I created three different geological models (from more homogenous (simple) to more complex). In addition, for each geological model, I assumed different numbers of noise sources and noise boundaries using the finite-difference method. After retrieving reflection responses, the results obtained for surface seismic and zero-offset VSP were compared with the synthetic seismogram. According to the results, when the geology is homogeneous (i.e., flat layering), the source distribution is wide and the number of point sources is high, the surface seismic data acquisition offers a better image of subsurface compare to VSP. However, once the geology becomes more complex, the source distribution is narrow, and the number of sources is limited, the VSP method can detect some of layers that have not been identified by the surface seismic method. Nevertheless, as I show, by combining the results from the two methods, we can obtain a better idea about subsurface layering. In other words, the two methods can complement each other. Thus, I propose the simultaneous surface seismic and zero-offset VSP data acquisitions for body wave ANSI.

Download

Share

COinS