• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.28 no.6
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• pp.645-653
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• 2010

In this study, IGS(International GNSS Service) stations were processed by the method of PPP(Precise Point Positioning), and velocities of crustal movements about the region of the Korean Peninsula were calculated precisely. The characteristics of crustal movements around Korean Peninsula were understood by velocity calculation of crustal movements. We confirmed from the result which calculated by crustal movement velocity shows the movement Eurasia and North America plate move to south-east, and Philippine plate moves to north-west. This result is respected to be utilized as a basic data about analysis of earthquake and earth physics.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2004.11a
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• pp.61-64
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• 2004

현재 GPS를 이용한 위성측위시스템은 기존의 DGPS에 의한 정밀도 향상 차원을 넘어 상시관측소를 활용한 기준국의 활용 증대 및 다양한 동시 사용자의 욕구를 충족시키기 위해 여러 가지 연구들이 진행되고 있다 현재 국내 연구동향으로 VRS-RTK (Virtual Reference Station Real Time Kinematic)에 대한 기초 연구가 진행 중에 있으며 해양수산부의 전파를 이용한 비콘 방식과 표준과학연구원 천문대에서는 MBC와 연계한 FM-DARC(Data Radio Channel)방식 등이 활용 방안으로 준비중에 있으며, 여러 기관과 대학 연구 기관에서 기초 연구가 진행 중에 있다. 따라서 이미 독일, 싱가폴, 일본 등에서 활용하고 있는 VRS의 연구를 보다 심화하여 현재 각기 다른 기관에서 보유하고 있는 70여개의 GPS 상시관측소의 효율적인 활용과 대 국민 서비스를 제공할 수 있는 시스템이 절실히 필요한 시기이다. 따라서 본 논문에서는 이런 가상관측의 결과를 산출할 수 있는 통계학적 모델링을 통한 가상관측 보정값을 산출할 수 있는 보정값을 제시할 수 있는 알고리즘 개발에 그 목적이 있다. 향후 알고리즘 개발이 완료되면 통계학적 모델링을 통해 단일 기준점에 의한 GPS 측량에서 불가능한 위치 결정 네트웍의 가상 관측을 가능하게 할 것이며, 신뢰성 있는 미지정수 해를 만들 수 있을 것이다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.5
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• pp.2390-2395
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• 2012

Monitoring of crustal movement by earthquake is an important line of study in geophysics and geodesy. In this Study, before and after the earthquake data about nine IGS permanent stations were processed by Precise Positioning System to analysis the influence area about Japanese earthquake in March 11 at 2:46pm. As the result of crustal deformation monitoring, the quantitative earthquake displacement and change of crustal movement was presented. Crustal movement monitoring using continuous GPS data processing is necessary for crustal research and predicting earthquake because crustal movement assumed a new aspect before and after the earthquake in Japan.

• Journal of Korean Society for Geospatial Information Science
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• v.12 no.1 s.28
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• pp.55-62
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• 2004

More recently, multiple reference based RTK GPS techniques(VRS ; Virtual Reference System) are becoming increasingly important for many precise GPS applications in many countries to overcome the constrained distance limitations of standard RTK systems. The precision of the position solutions of the rover receiver is closely connected with that of the corresponding virtual reference points(VRPs). The objective of this paper is to investigate the accuracy and performance of the VRPs on the test network have been made in post mode, and the overall analysis results were presented by comparing the solutions for the VRPs from the existing GPS reference station with the true values of the coordinates used to produce the observation data. The results show the reasonable accuracies of VRPs in the network area by using the VRS concept in post mode.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.3
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• pp.311-318
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• 2011

On March 11, 2011, an 9.0-magnitude earthquake occurred near the northeastem coast Japanese. It was the largest earthquake that hit Japan since the beginning of modern seismometry. The earthquake occurred 179km east of the Sendai, Miyagi Prefecture, leaving about 27,000 of people confirmed dead, injured or missing due to the earthquake and tsunami. In this study, crustal Deformation in Mizusawa, Tsukuba and Usuda station were calculated based on GPS data in IGS station of Japan. The observation data were processed by precise point positioning and relative-positioning method using on-line GPS data processing services and a high precision scientific GPS/GLONASS data processing software. The coseismic displacements in IGS stations before and after the earthquake were analyzed using kinematic precise point positioning method, and the crustal deformation of the areas before and after the earthquake were precisely calculated using the relative-positioning method. The results of the study calculated precise coordination that the RMSE is maximum ${\pm}0.003m$, respectively and showed that Mizusawa station moved 2.6m southeast by the earthquake.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.5
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• pp.599-605
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• 2009

Changes of atmospheric pressures cause short- and long-term crustal deformations and thus become error sources in the site positions estimated from space geodesy equipments. In this study, we computed daily displacements due to the atmospheric pressure loading (ATML) at the 14 permanent GPS sites operated by National Geographic Information Institute. And the 10-year GPS data collected at those stations were processed to create a continuous time series of the height estimate. Then, we corrected for the ATML from the GPS height time series to see if the correction changes the site velocity and improves the precision of the time series. While the precision improved by about 4% on average, the velocity change was not significant at all. We also investigated the overall characteristics of the ATML in the southern Korean peninsula by computing the ATML effects at the inland grid points with a $0.5^{\circ}{\times}0.5^{\circ}$ spatial resolution. We found that ATML displacements show annual signals and those signals can be fitted with sinusoidal functions. The amplitudes were in the range of 3-4 mm, and they were higher at higher latitudes and lower at the costal area.

• Geophysics and Geophysical Exploration
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• v.16 no.3
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• pp.190-195
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• 2013

We estimated near-surface shear-wave velocity (${\nu}_s$) at the Hwacheon seismic station using a geologic log of a well, microtremors recorded during a period of 56 days, and records of three teleseismic events ($M_w{\geq}6.0$). The vs of the 10-m thick soil layer (${\nu}^s_s$= 296 m/s) was determined from horizontal-to-vertical spectral ratios of microtremors recorded at the surface. The average ${\nu}_s$ ($\bar{\nu}_s$= 1,309 m/s) from the surface to the 96-m depth of a borehole sensor, was computed using spectral coherence analyses of data recorded by surface- and borehole-sensors for the three teleseismic events. Using these calculated values of ${\nu}^s_s$ and $\bar{\nu}_s$, the computed bedrock ${\nu}_s$ is 2,150 m/s and the time-averaged ${\nu}_s$ to a 30-m depth is 696 m/s. Accordingly the Hwacheon seismic station is regarded as a relatively good site. The deduced near-surface ${\nu}_s$ can be used for further quantitative evaluation of site amplification and earthquake hazard.

• Journal of the Korean earth science society
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• v.44 no.6
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• pp.594-610
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• 2023

The horizontal-to-vertical spectral ratio (HVSR) has been widely applied to evaluate ground characteristics such as site response and thickness of the soft sedimentary layer on top of the bedrock via dominant frequencies and amplification factors of microtremors. Eight seismic stations were selected to investigate the HVSR results at the surface and at varying depths, and their variations due to wind speeds. These stations are equipped with seismic sensors on the surface and downhole(s) at depths. The borehole data analysis reveals that the geological condition at burial depth influences the HVSR results. Their dominant frequencies indicate the entire thickness of the soft layer, not the thickness to the bottom or top of the soft sedimentary layer from the seismometer burial depth. Analysis of the background noise observed at the surface showed that the resonance frequency estimation varied with wind speed changes. In the studied cases, the background noise observed in the sedimentary layer at depths of 20 to 66 meters yielded stable and consistent resonance frequency estimation regardless of wind speed fluctuations. The results of the seismic sensors buried deeper than 100 meters are unstable. The result indicates that the background noise from the buried seismometer at shallow depths (~0.3 m) under light wind conditions (wind speeds less than 3 m/s) is sufficient to achieve the purpose of the HVSR analysis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2D
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• pp.317-324
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• 2006

This study deals with the precise GPS data processing refer to ITRF2000 through the calculation of absolute coordinates of cadastral satellite station which were established by purpose of cadastral surveying. We used the Gipsy-Oasis II software developed Jet Propulsion Laboratory to estimate daily position of GPS stations with orbital and atmospheric parameters. Especially, we carried out ionospheric delay, tropospheric delay, data existence whether or not and quality control check of observation data during pre-processing. The standard deviation of absolute coordinates was determined better than ${\pm}4mm$ from GPS precise analysis. The RMSE of difference between the result of this study and existing result by using Bernese s/w shows ${\Delta}X={\pm}0.079m$, ${\Delta}Y={\pm}0.019m$ and ${\Delta}Z={\pm}0.031m$.

• Journal of the Korean GEO-environmental Society
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• v.10 no.1
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• pp.35-41
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• 2009

It is necessary to consider the site amplification for estimating SSI (soil structure interaction) and seismic source with more confidence. The horizontal to vertical (H/V) ratio technique in spectral domain is one of several techniques to estimate empirical site transfer function. The technique, originally proposed by Nakamura (1989), is applied to analyze the surface waves in the microtremor records. However, the application of this technique has been widened to the shear wave energy of strong motions for estimating site amplification. The purpose of this paper is to estimate spectral ratio using observed data at the seismic stations distributed within Southern Korean Peninsula from the Fukuoka earthquake including 11 aftershocks. The results show that each station has the its own characteristics of the specific resonance, high-band, and low-band frequency. The characteristics of the resonance frequency is more important because the quality of the seismic records are dependent on the resonance frequency. The result can be used for the study of site classification and removal of the site amplification effects from observed records can give us more reliable seismic source parameters.