5성분 지오폰의 다운홀 탄성파탐사 적용 가능성 연구

A feasibility Study of the 5-component Geophone for Down-hole Seismic Surveys

  A new 5-component borehole geophone is proposed and tested for down-hole seismic surveys. Since the traditional borehole geophone is designed to measure 3 components of movement, i.e., 2 horizontal components(x and y directions) and one vertical component(z direction), it is difficult to identify S-wave arrivals when one of the horizontal geophone is not in the same plane with the direction of the strike on the surface. In order to overcome those difficulties and to measure incoming of S-wave in many directions the proposed 5-component borehole geophone consists of one vertical geophone and 4 horizontal geophones which are oriented 45 degrees apart. Also, the 5-component borehole geophone has air packer at the lower part of the borehole in order to stick the geophone to the borehole wall when measuring. A field test was conducted at Eulsookdo test site, and the results show that using a 5-component geophone for down-hole seismic survey is superior to conventional 3-component geophone in identifying S-wave arrivals, and it can be applied to develop a seismic cone, one of the in-situ soil instruments measuring rigidity modulus of soil without a borehole.