• Journal of the Korean Geophysical Society
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• v.2 no.1
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• pp.57-64
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• 1999

To effectively identify near-surface faults with vertical slips from seismic refraction data, the GRM interpretation technique is tested and investigated in terms of various parameters through computer modeling. A characteristic change in shape of the velocity-analysis function near faults is noticed, and a new strategy of `Slope Variation Indicator (SVI)' is developed and tested in this study. The SVI is defined as a first horizontal derivative of the difference of velocity analysis functions for a large XY value and a small one, respectively. As the dip of refractor decreases and as the difference in XY value increases, the peak value of SVI increases and its duration decreases. Consequently, the SVI indicates accurately the location of buried fault in the test models. The SVI is believed to be an efficient tool in seismic refraction method to investigate location and distribution of shallowly buried faults.

• Journal of the Korean Geophysical Society
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• v.2 no.1
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• pp.65-74
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• 1999

From refraction data along four seismic profiles near Eonyang which the Yangsan fault passes through, the Slope Variation Indicators (SVI) are computed and interpreted in terms of fault distribution. The average velocities of 2,250-2,870 m/s are estimated using velocity-analysis functions for the target boundary along those profiles. The average velocity for Line 1 is approximately 600 m/s lower than ones for the other lines. The SVI's with amplitude greater than or equal to 0.5 ms/m are turned out to be located near faults shown on the high-resolution reflection section, as closely as one station spacing (3 m). Large amplitude SVI's are densely distributed near National Road 35, and the fault having the largest vertical slip is indicated to be located approximately 930 m west of the inferred fault on the published geologic map.