• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.370-378
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• 2003

Continuous seismic refraction, reflection and echo-sounder surveys conducted at Koyna Project site provided geotechnical information which helped in choosing the alignment for Head race tunnel and in designing and choosing the site for Lake Tap. Seismic refraction survey both on land and in shallow water determined depths to bedrock and helped in inferring the bedrock quality. Seismic reflection survey mapped the subsurface stratigraphy with high resolution. Reservoir-bed and bedrock contours drawn from the results of the survey helped in choosing the tunnel alignment and the lake tap position cost effectively. It was inferred from the results of the survey that the geology and the quality of rock do not change unexpectedly around the site for extension of Head race tunnel and the lake tapping. The bedrock levels evaluated by seismic survey agreed remarkably well with those inferred in boreholes having Rock Quality Designation 90 percent or more.

• 한국지구물리탐사학회:학술대회논문집
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• 2002.09a
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• pp.101-125
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• 2002

A lake seismic survey was carried out to investigate possible geohazards for construction of the underground LPG storage at Namyang Lake. The proposed survey site has a land-lake combined geography and furthermore water depth of the lake is shallow. Therefore, various seismic methods such as marine single channel high resolution seismic reflection survey, sonobuoy refraction survey, land refraction survey and land-lake combined refraction survey were applied. Total survey amounts are 34 line-km of high resolution lake seismic survey, 14 lines of sonobuoy refraction survey, 890 m of land refraction survey and 8 lines of land-lake combined refraction survey. During the reflection survey, there were severe water reverberations from the lake bottom obscured subsurface profiling. These strong multiple events appeared in most of the survey area except the northern and southern area near the embankment where seems to be accumulated mainly mud dominated depositions. The sonobuoy refraction profiles also showed the same Phenomena as those of reflection survey. Meanwhile the results of the land-lake combined refraction survey showed relatively better qualities. However, the land refraction survey did not so due to low velocity soil layer and electrical noise. Summarized results from the lake seismic survey are that acoustic basement with relatively flat pattern appeared 30m below water level and showed three types of bedrock such as fresh, moderately weathered and weathered type. According to the results of the combined refraction survey, a velocity distribution pattern of the lake bottom shows three types of seismic velocity zone such as >4.5 km/s, 4.5-4.0km/s and <4.0km/s. The major fault lineament in the area showed NW-SE trend which was different from the Landsat image interpretation. A drilling was confirmed estimated faults by seismic survey.

• 한국지구물리탐사학회:학술대회논문집
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• 2009.05a
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• pp.73-87
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• 2009

Geophysical survey for unconformity-type uranium deposit applied to this study area in Athabaska Basin, Canada were carried out airborne TEM and magnetic, resistivity-induced polarization (DC-IP), puser seismic reflection and well-logging method. The results of airborne survey interpreted the lithological boundary, geological structures, and conductors. Also, these results decided to main targets for ground DC-IP survey. The Low resistivity and the high chargeability slices of 3D modeling interpreted from DC-IP survey response for conductors related to hydrothermal alteration zones and fault-controlled graphitic zones occurring at the unconformity-type uranium deposit, and they confirmed by diamond drilling. Seismic results interpreted to lake bottom surface, alluvium layer and intra-sandstone faults. We suggest the resonable field data acquisition of DC-IP method on the land or the lake in Athabaska Basin.

• Journal of the Korean Geographical Society
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• v.41 no.4 s.115
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• pp.391-403
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• 2006

The Hanon volcano located in the southern pan of Cheju Island, Korea has a wetland in its crater being used as a farmland. Previous researchers presumed this wetland was a maar lake in the past. Based on the seismic refraction method, the wetland sediment layer was estimated between 5 to 14 m deep, which is mostly in accordance with previous researches. However, this shows only the depths at some sites, not representing the whole spatial distribution. This study is an attempt to reconstruct the volcanic lake in Hanon crater by applying the spatial statistical techniques based on the depth information from the seismic survey and known data. The procedure of reconstruction is as follows: First, the depth information from the seismic survey and known data were collected and it was interpolated by IDW and Ordinary Kriging method. Next, with the interpolation map and the present DEM the paleo DEM was constructed. Finally, using the paleo lake level on core data, the boundary of volcanic lake was extracted from the paleo DEM. The reconstructed lake resembles a half-moon in the north of the central scoria cone. It is estimated that the lake was 5 m deep on average and 13 m deep at the deepest point. Although there are slight differences according to the interpolation techniques, it is calculated that the area of the lake was between 184,000 and $190000m^2,$ and its volume approximately $869,760m^3$. Because of the continuous deposition processes after the crater formation, the reconstructed volcanic lake would not indicate an actual lake at a specific time. Nevertheless, it offers a significant clue regarding the inner morphology and evolution of the crater.

• Journal of the Korean Geophysical Society
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• v.2 no.4
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• pp.251-258
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• 1999

A high-resolution seismic survey was conducted on the abandoned tidal flat in Shihwa Lake on the west coast of Korea. A portable vibrator was used as a seismic source and 217 shot gathers with 48-channel system were acquired. F-k filtering, residual static corrections and post-stack frequency filtering are found to be useful for signal enhancement. The overburden is divided into two seismic depositional units. Unit I is deposited in tidal environment characterized by parallel and high continuity reflection pattern. This unit comprises a dry layer (Unit Ia) and a wet layer (Unit Ib) having averagely 5 and 15 meters thick, respectively. Unit II unconformably overlain by Unit I exhibits discontinuity and hummocky reflection pattern, indicating complex channel-fill sediments in estuary. The maximum thickness of this unit is approximately 20 meter. Acoustic basement is considered as Precambrian granitic gneiss occurred in the surrounding area.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.449-454
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• 2003

The accurate mapping of the basement is one of the most crucial factors in construction of harbour facilities and bridges in the coastal areas. In shallow waters, the seismic reflection method often fails to image the basement geometry beneath the sediment cover in many cases. We present the result of a shallow marine seismic refraction survey using two ships, l2-channel hydrophone arrays deployed on the bottom and a borehole sparker or percussion powder as sources. Velocity structure could be computed by tomography algorithm since more than 6 different source points had been applied for one spread. The comparison of the results of the refraction survey with drilling logs demonstrates remarkable consistency in basement geometry. It thus appears that the refraction method in this study is an efficient and cost-effective way to investigate the basement structure in coastal area, river, and lake.

• Journal of the Korean Geophysical Society
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• v.9 no.4
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• pp.343-349
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• 2006

In order to study unconsolidated sediments upstream of the Soyang Dam, seismic refraction data were recorded along five profiles of 94 m length. Receiver interval and record length were 2 m and 204 ms, respectively. Recorded data were analyzed using the traveltime tomography and delay-time methods in order to reveal sediment distribution in the investigation site. The acoustic basements are buried at approximately 14 m deep and their thickness shallows to southeast approaching to a hill. On the basement, pre-existing sediments deposited before construction of the Soyang dam lies. This sedimentary layer is composed of paleo-soil and sandy sediments. Above this layer, recent sediments comprise the top layer which is believed to have been deposited since the formation of the dam. Average thickness of this uppermost layer is approximately 1.6 m, which is much thicker than in the downstream.