고정밀 중력 탐사를 위한 3차원 중력 지형 역산 기법 = 3-D Gravity Terrain Inversion for High Resolution Gravity Survey

다국어 초록 (Multilingual Abstract)

Recently, the development of accurate gravity-meter and GPS make it possible to obtain high resolution gravity
data. Though gravity data interpretation like modeling and inversion has significantly improved, gravity data processing
itself has improved very little. Conventional gravity data processing removes gravity effects due to mass and height
difference between base and measurement level. But, it would be a biased density model when some or whole part of
anomalous bodies exist above the base level. We attempted to make a multiquadric surface of the survey area from
topography with DEM (Digital Elevation Map) data. Then we constituted rectangular blocks which reflect real topography
of the survey area by the multiquadric surface. Thus, we were able to carry out 3-D inversions which include information
of topography. We named this technique, 3-D Gravity Terrain Inversion (3DGTI). The model test showed that the
inversion model from 3DGTI made better results than conventional methods. Furthermore, the 3-dimensional model from
the 3DGTI method could maintain topography and as a result, it showed more realistic geologic model. This method was
also applied on real field data in Masan-Changwon area. Granitic intrusion is an important geologic characteristic in this
area. This method showed more critical geological boundaries than other conventional methods. Therefore, we concluded that in the case of various rocks and rugged terrain, this new method will make better model than convention ones.

국문 초록 (Abstract)

최근에수행되고있는중력탐사는고분해능의중력계와 GPS(Global positioning system) 를통한정밀한측정과측지가이루어지고있다. 중력탐사에서모델링과역산의기술은많은발전이있어왔지만, 중력자료처리는거의변화가없었다. 통상적인정밀한중력자료보정을통한부우게이상은측정점의고도에서기준면까지의물질의영향을일정한밀도를이용해제거해버리기때문에측정점바로하부의이상체에의한영향을상당히왜곡시키게된다. 본연구에서는탐사지역의지형을 DEM(Digital Elevation Map) 자료와 Multiquadric equation 을이용하여실제지형과유사한Multiquadric surface 를자동적으로구성하고, 이를블록화함으로써보정의대상이었던기준면상부에대한밀도를탐사지역의지질정보와지형을포함하는역산을통해수치적으로계산하였다. 이러한지형을포함한역산방법을 3차원중력지형역산(3DGTI; 3-D Gravity Terrain Inversion) 이라한다. 이연구의효율성을검증하기위하여주변암과밀도차가존재하는관입지역에대한모델을구성하고적용한결과기존의부게보정방법을적용한부게이상도에비해자료의왜곡이감소하는효과를얻을수있었다. 이를통하여지형역산을통한객관적인부게밀도의결정과부게보정시실제의수평적인밀도변화를반영함으로써기존의문제점을보완하였다. 게다가, 3DGTI 로부터얻어진밀도분포는지형의윤곽을그대로표현하고있어서보다실질적인지질을보여준다고하겠다. 이방법을화강암체가관입하고있는마산·창원일대에서의중력탐사자료에적용해본결과기존방법보다관입화강암체의위치와그규모를알아내는데더효과적이었다. 따라서, 수평적인밀도변화가뚜렷하게존재하는지역의경우, 새로운중력자료처리방법이기존

참고문헌 (Reference)

• 1 "중력측정자료에대한지형보정을위한기술개발 ." 한국자원연구소 1998
• 2 "다중이차곡면방정식을이용한중력자료의지형보정" 156-165, 1990
• 3 "Rapid computation of gravitational attraction of three-dimensional bodies of arbitrary shape" 203-225, 1960
• 4 "Determination of density for reduction of gravimeter observation" 1939