• Journal of the Korean Geophysical Society
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• v.8 no.2
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• pp.67-74
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• 2005

Two-dimensional S-wave velocity sections from SH-wave refraction tomography and surface wave dispersions were obtained by inverting traveltimes of first arrivals and surface wave dispersions, respectively. For the purpose of comparison, a P-wave velocity tomogram was also obtained from a P-wave refraction profiling. P and Rayleigh waves generated by vertical blows on a plate with a sledgehammer were received by 100- and 4.5-Hz geophones, respectively. SH-waves generated by horizontal blows on both sides of a 50 kg timber were received by 8 Hz horizontal geophones. The shear-wave signals were enhanced subtracting data of left-side blows from ones of the right-side blows. Shear-wave velocities from tomography inversion of first-arrival times were compared with ones from inverting dispersion curves of Rayleigh waves. Although the two velocity sections look similar to each other in general, the one from the surface waves tends to have lower velocities. First arrival picking of SH waves is troublesome since P and PS-converted waves arrive earlier than SH waves. Application of the surface wave method, on the other hand, is limited where lateral variation of subsurface tructures is not mild.

• Journal of the Korean Geophysical Society
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• v.8 no.2
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• pp.81-87
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• 2005

Acquisition and processing of vector seismic waves were conducted through simultaneous generation of P, SH, and SV waves and receiving those waves using three-component geophones. Test data were received by 24 8-Hz geophones at an interval of 2 m along a 94-m profile. The data were recorded for 512 ms with sampling intervals of 0.2 ms. Raw data indicate that both reflected and refracted P waves are strongly recorded on the vertical component while SH waves are significant on the transverse horizontal component. On the inline horizontal component, both direct P and converted PS waves are recorded. First arrivals of P and SH waves were detected simultaneously on the vertical and transverse horizontal axes, respectively. The recorded vector data were separately inverted using traveltime tomography to yield P- and SH-wave sections. Using those two velocity sections, Poisson's ratios were able to be obtained effectively.

• Journal of the Korean Geophysical Society
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• v.8 no.2
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• pp.93-96
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• 2005

Focal mechanism of the real and imaginary faults in the western coast of Japan has been assumed by examining the previous studies on the seismicity, seismic gap, fault behaviors, seismic zoning, and faults. In the area of no seismic information, the focal mechanism has been assumed to have the maximum influence on the tsunami height in the eastern coast of Korea. The tsunami height in a particular point of the eastern coast of Korea can vary up to 7 orders with the variation of the strike of the fault in a particular source point of the western coast of Japan with constant magnitude. Tsunami scenario DB including the arrival times and tsunami heights has been constructing by using the assumed focal mechanism of the western coast of Japan. Tsunami warning system will be reinforced by using this tsunami scenario DB near future.

• Journal of the Korean Geophysical Society
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• v.10 no.1
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• pp.37-44
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• 2007

Nowadays, Global Navigation Satellite System(GNSS) which is the new concept of positioning system has been developed because of satisfaction human's intelligent desire and rapid science development. GNSS which is represented by GPS provides 3-Dimension positioning information not expensively in whenever, wherever. The industry of positioning information has extending civil market widely as well as military market. So GNSS is running the role of society infra structure including car and airborne navigation, civil engineering, GIS resource, telematics and LBS, and so on. As USA removes the SA(Selective Availability), GPS has monopolizing the market and other countries have been depended on GPS, absolutely. In this paper, the author developed the software for analysis of influence using next generation, Galileo system. The local analysis was performed according to positioning mode. And GPS/Galileo combined system can implement positioning in the worst mask environment like urban cannon.

• Journal of the Korean Geophysical Society
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• v.10 no.1
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• pp.27-35
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• 2007

There are many risks in constructing tunnel-structure. To prevent these risks from occurring and secure safety, the precise and rapid survey of inside displacement of the tunnel is required. But nowadays the measurement of the crown settlement, convergency, and surface settlement depends on general kinds of method which use total station or level. In the way to provide data about maintaining structure according to recent improvement and progress of measuring technology, 3D laser scanning is used. It solves the problem of reliability in measuring displacement of existing structure, provides material that enables to estimate shape change of structure visually, and makes it possible to deliberate speedy countermeasure. By this three dimensioning it is possible to make efficient use of structure maintenance and field measurement.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.137-140
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• 2008

During CHAOS (2003, 2006) and SSGH projects (2007), acoustic investigation including hydroacoustic (HA), side-scan sonar (SSS) and highresolution sparker seismic (HSS) surveys was carried out on the northeastern Sakhalin slope ($53^{\circ}56'\;N$, $143^{\circ}52'\;E$ to $54^{\circ}40'\;N$, $144^{\circ}32'\;E$). More than 130 methane seeps with high backscatter intensity are identified on SSS mosaic, which are well accompanied with gas flares in the water column on HA profiles and subbottom gas chimneys on HSS profiles. It is likely that that some seeps align along a NW strike parallel to the Lavrentiev Fault.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.125-130
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• 2008

Electrical resistivity and seismic refraction surveys were conducted to investigate geologic structures and geotechnical characteristics of the subsurface in Dok-do island, along with rock physical properties. The resistivity results in Seo-do island show that the fault adjacent to the fisherman's shelter is a normal fault and extended towards the NW direction. Bedded Rapilli Tuff in the downstream was more severely influenced in depth by weathering and erosion than Trachy Andesite II in the upstream area. The physical properties of the rocks illustrate that Trachyte and Trachy Andesite are hardest, Massive Tuff Breccia is next, and Tuffs are the most soft rocks in Dok-do island.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.107-112
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• 2007

To establish the reinforce region and technique through the embankment dike after identifying the region of seawater inflow, we carried out small-loop electromagnetic (EM) survey, electrical resistivity survey and refraction seismic method. We also analyzed the distribution of electrical conductivity in reservoir with depth every two month and monitored water level variations with tidal variation in four observation wells located at seaside and reservoir side in order to analyze the relationship with survey results. From both the cross-correlation between tidal and water level variation at four wells and the distribution of electrical conductivity in reservoir with depth, the major portion of seawater inflow are identified through the embankment dike. From electromagnetic and electrical resistivity survey results, it was found that the seawater inflow were happened through several small regions at seaside and became wider near reservoir side. The 2-D inversion sections of refraction seismic method showed that the pebble-bearing sand layer is spread over the whole region with two to four width. From the this study, small-loop EM, electrical resistivity and refraction seismic surveys accompany with the distribution of electrical conductivity in reservoir with depth and the monitoring results for water level variations are revealed to be effective to identify seawater inflow pathway through embankment dike and to establish the reinforce region and technique through the embankment dike.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.267-272
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• 2007

Uiseong subbasin belonging to Kyungsang basin resulted from volcanic activity in the late Cretaceous. In this study, we carry out MT and gravity survey at the Hwasan caldera, which was formed of volcanic and abyssal rocks complex, then analyze and identify geological substructure. Potential survey such as gravity and magnetic survey has been mainly carried out in former studies, so depth information for understanding substructure was not enough. To complement a potential survey, we use MT method, which has high vertical resolution. Moreover we make a simple 2D model comparing with former study. The result of MT and gravity 2D modeling shows that this area is roughly composed of 3 layers; The bottom layer is a basement. In the second layer, intrusive rocks having high resistivity is placed along the ring faults and the sedimentary layer of low resistivity is inside caldera. The highest layer is alluvium. To comprehend the 3D structure of the Hwasan caldera, we perform 3D gravity inversion, and construct the 3D model from the result of 3D gravity inversion. MT responses are calculated by using the constructed 3D model and the 3D model of the Hwasan caldera's structure is suggested after comparing the calculated values with the observed values at MT line.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.7-11
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• 2008

기상청은 2008년 현재 전국에 107개의 디지털 지진관측망을 운영하고 있다. 또한 지진관측 유관기관인 한국지질자원연구원, 한국원자력안전기술원, 한전전력연구원에서 각 기관의 목적에 맞게 지진관측소를 운영하고 있으며, 이들 지진관측자료의 공유를 목적으로 실시간으로 통합하는 통합지진과측망(KISS)을 2000년에 구축하여 지진분석에 쓰이고 있다. 한반도의 지진발생 현황은 1978년부터 2007년까지 776회로 약 26회/년 정도가 발생하였다. 최근 중국의 쓰촨성과 일본 이와테 지진으로 지진 및 지진예지에 대한 국민적 관심이 대두되고 있다. 한반도에서도 큰 규모의 지진이 발생할 가능성에 대비해 기상청에서는 지진관측망과 지진예지 목적의 지구물리관측망을 구축 중에 있다. 지구물리관측망은 INTERMAGNET에서 등록할 수 있는 수준의 관측소를 목표로 인위적인 자기장의 교란이 적은 지질학적인 요소들을 고려한 후보지 선정을 위하여 지구자기업무에 관한 기획연구(서만철 2007)를 수행 하였다. 그 결과 국가 중심 지구자기관측소의 위치는 충남 공주시와 청양군 사이에 있는 칠갑산 지역이 가장 좋은 후보지라고 제안하여 청양지역을 주변으로 국유림 및 군유지를 조사하여 충남 청양군 장평면 화산리 산 36-2번지에 후보지를 선정하여 최적의 입지 조건을 검증하기 위해 인천교육대학교의 이휘순 교수 MT탐사를 수행 주변의 배경잡음을 측정하여 양호한 조건을 갖춘 것으로 확인되었다. 지구자기관측소에는 Fluxgate Magnetometer 1대, Total field Magnetometer 1대, Theodolite 1대, SP(Self Potential) Monitoring system 1대와 장비들을 보호 할 수 있는 관측소가 설치될 예정이다