花崗岩分布地域を対象としたマルチオフセットVSP探査

Multi-offset VSP Survey in Area of Granite distribution

新沼 岩保*; 相澤 隆生*; 伊東 俊一郎*

Niinuma, Iwao*; Aizawa, Takao*; Ito, Shunichiro*

本業務は広域地下水流動研究の一環として、サイクル機構が掘削したボーリング孔を利用してVSP探査、物理検層、ボアホールテレビューア計測を実施し、取得されたデータの解析を行ったものである。本業務の目的は、ボーリング孔で遭遇する花崗岩内部の断層破砕帯や割れ目などに対応する弾性波応答の把握および、花崗岩分布におけるボーリング孔周辺の地質構造分布、試錐孔と交差する割れ目帯等の連続性などを把握する上でのVSP探査手法の確認を行うことにある。

A Vertical Seismic Profiling(VSP), Geophysical Logging and Borehole televiewer (BHTV) were performed in borehole 03RT-03. The objectives of this work are to obtain of the elastic wave response corresponding to fractures and fault zones in the granite, and to understand the application of VSP technique to survey continuity of fault zones or fractures in granite. The contents of this survey were presented in this report. In VSP survey, five shot points were set along the direction of borehole drilling. VSP processing and 3D imaging of seismic reflector were performed in order to obtain the continuity and directivity of fault zones or fractures. The events in seismic processing section, corresponding to fault zone or fractures in the granite, accepted by core information. The results of those processing were compared with the geological information acquired from the data of Geophysical logging and BHTV.