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    The effect of terrain topography on commonly used resistivity arrays
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    Abstract:
    In this work a study of the effect of surface topographical variations on several dc resistivity arrays is presented. A 2.5-D finite‐element modeling scheme is used to examine the performance of several arrays over buried features that exist below a range of different topographical terrain contexts, such as valleys, hills, and steep slopes. A mesh‐generating algorithm allows a realistic representation of terrain topography. The results confirm that topographical variations can have a significant impact on the field resistivity data values for all resistivity arrays. Further, topographical variations can be treated flexibly using a realistic resistivity forward modeling process. Thus, topographic effects, to the degree they can be modeled, are predictable and should be taken into account when designing surveys and interpreting data.
    Keywords:
    Representation
    Electrical Resistivity Tomography
    In more recent times Electrical Resistivity Tomography (ERT) has become a valuable tool for many<br>environmental research themes. Within these topics the resistivity contrasts of the different layers and<br>zones are of importance, i.e. sand, clay, water salinity and preferential infiltration pathways are quite<br>small. Inclusions with such small resistivity contrasts to the surrounding are difficult to resolve by ERT<br>inversion and typically the following problems occur: 1.) the true resistivity contrasts are underestimated<br>2.) the size of the anomalous zone is overestimated 4.) fake anomalies arise beside and between the true<br>anomalous zones. 4.) surface heterogeneities infer fake anomalies into the subsurface.
    Electrical Resistivity Tomography
    Infiltration (HVAC)
    그 동안 많은 연구에서 지형보정을 위한 프로그램들이 개발되어왔으며, 매우 효과적으로 지형보정을 수행하는 것으로 인정받아왔다. 특히, 한반도 뿐만이 아니라 세계적으로도 수치 지형자료가 보편적으로 보급되어 지형보정을 위한 기반 자료는 충분히 확보되고 있다. 이번 연구는 일반적인 광역탐사가 아닌 소규모 광체나 지질구조에 대한 정밀한 중력탐사에 대한 자동지형보정을 수행할 수 있도록 하는 프로그램을 개발하였다. 소규모 지하자원이나 지하공동 등의 소규모 지질현상에 대한 중력탐사에는 기존의 광역탐사에 적합한 지형보정프로그램보다 더욱 정밀한 지형보정프로그램이 필요하다. 따라서 본 연구를 통해서 개발된 자동정밀지형보정프로그램으로 정밀중력탐사를 보다 효율적으로 수행할 수 있게되었다. 본 연구에서 개발된 정밀지형보정프로그램에서는 multiquadric equation을 이용한 지형구현을 통해 보다 정밀한 지형 생성이 가능하게 설계하였으며, 연구자의 설정에 따라 중력측정점 주변에 자세한 지형값을 넣어 정밀한 지형보정이 가능하도록 하였다. 또한 기존의 광역중력탐사에서 무시되던 지형과 중력계 사이의 거리 차에 따른 옵션을 설정하여 정밀한 지형보정 수치를 산출하도록 하였다. Many studies have successfully developed a number of terrain correction programs in gravity data. Furthermore, terrain data that is a basic data for terrain correction has widely been provided through internet. We have also developed our own precise gravity terrain correction program. The currently existing gravity terrain correction programs have been developed for regional scale gravity survey, thus a more precise gravity terrain correction program needs to be developed to correct terrain effect. This precise gravity terrain program can be applied on small size geologic targets, such as small scale underground resources or underground cavities. The multiquadric equation has been applied to create a mathematical terrain surface from basic terrain data. Users of this terrain correction program can put additional terrain data to make more precise terrain correction. In addition, height differences between terrain and base of gravity meter can be corrected in this program.
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    Electrical Resistivity Tomography