Development of passive seismic interferometry to study shallow subsurface structure

• Main Author: Afonin, N. (Nikita)
• Other Authors: Kozlovskaya, E. (Elena), Lunkka, J. (Juha-Pekka)
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Oulun yliopisto 2022
• Subjects: ambient seismic noise; empirical Green’s function; mechanical rock properties; passive seismic interferometry; seismic velocities; shallow subsurface; empiirinen Greenin funktio; maankamaran pintaosa; mekaaniset kallion ominaisuudet; passiivinen seisminen interferometria; seismiset nopeudet; ympäristön seisminen melu; Kuusamo; Sodankylä; Suasselkä; Fennoscandian
• Online Access: http://urn.fi/urn:isbn:9789526234632

Abstract This thesis presents the results of the development passive seismic interferometry technique and its application for studying shallow subsurface structure in the stable intraplate area of the Precambrian Fennoscandian Shield. Knowledge about structure and mechanical properties of this part of the geological medium is important in the most applied tasks, such as mineral exploration, seismic hazard assessment, geotechnical site investigations, geoenergy projects. The thesis briefly describes the theoretical background of passive seismic interferometry, conditions for its application and describes the new algorithm for passive seismic data processing developed as a part of this work. This algorithm allows for improvement in the quality of empirical Green’s functions (EGFs) evaluated from ambient seismic noise wavefield, produced by non-uniformly distributed sources of high frequency (higher than 1 Hz). In comparison with the most conventional algorithms of passive seismic interferometry, the proposed algorithm requires a much shorter duration of passive seismic data acquisition time, because diffusivity of the wavefield in that case is mostly ensured by multiple scattering. The proposed methodology has been tested for several case studies located in different areas of Finland, that not only have different scales and targets, but also different spatial distribution and intensity of ambient seismic noise sources: Suasselkä postglacial fault — natural ambient seismic noise of relatively low- frequency; Kuusamo area — high-frequency noise of low energy; the area near the Pyhäsalmi underground mine — non uniform high-frequency seismic noise of high energy; Sodankylä area — anthropogenic and natural high-frequency seismic noise of low energy. Results of the case studies presented in the thesis have demonstrated that using conventional passive seismic interferometry in applied tasks is not always possible under conditions of the Fennoscandian Shield. The development of the data processing common workflow has ...