• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.34 no.3
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• pp.299-308
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• 2016

Various space geodetic techniques have been developed for highly precise and cost-efficient positioning solutions. By correcting the physical phenomena near the earth’s surface, the positioning accuracy can be further improved. In this study, the vertical crustal deformation induced by the ocean tide loading was accurately estimated through GNSS absolute and relative positioning, respectively, and the tidal constituents of the results were then analyzed. In order to validate the processing accuracy, we calculated the amplitude of eight major tidal constituents from the results and compared them to the global ocean tide loading model FES2004. The experimental results showed that absolute positioning and positioning done every hour during the observation time of 2 hours, which yielded an outcome similar to the reference ocean tide loading model, were better approaches for extracting tide constituents than relative positioning. As a future study, a long-term GNSS data processing will be required in order to conduct more comprehensive analysis including an extended tidal component analysis.

• Geophysics and Geophysical Exploration
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• v.18 no.3
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• pp.133-142
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• 2015

Displacement of the Earth's surface due to atmospheric loading has been recognized since a century years ago, and its accurate estimation is required in present day geodesy and surveying, particularly in space geodesy. Atmospheric load deformation in continental region can readily be calculated with the given atmospheric pressure field and the load Green's function, and, in near coastal area, approximate model is used for the calculation. The changes in the Earth's atmospheric circulation and the seasonal variation of atmospheric pressure on two hemispheres of the Earth are the each main causes of variation of the Earth's spin angular velocity and polar motion respectively. Wind and atmospheric pressure do the major role in other periodic and non-periodic perturbations of the positions in the Earth's reference frame and variations in the Earth's spin rotational state. In this reviewing study, the developments of related theories and models are summarized along with brief description of phenomena, and the geodetic perturbing effects of a hypothetical typhoon passing Korea are shown as an example. Finally related existing problems and further necessary studies are discussed in general.

• Geophysics and Geophysical Exploration
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• v.14 no.2
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• pp.127-132
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• 2011

We acquired and interpreted more than 650 km of high-resolution seismic reflection profiles in the Hupo Basin, offshore east coast of Korea at $37^{\circ}N$ in the East Sea (Japan Sea) to image shallow and basement deformation. The seismic profiles reveal that the main depocenter of the Hupo Basin in the study area is bounded by the large offset Hupo Fault on the east and an antithetic fault on the west; however, the antithetic fault is much smaller both in horizontal extension and in vertical displacement than the Hupo Fault. Sediment infill in the Hupo Basin consists of syn-rift (late Oligocene. early Miocene) and post-rift (middle Miocene.Holocene) units. The Hupo Fault and other faults newly defined in the Hupo Basin strike dominantly north and show a sense of normal displacement. Considering that the East Sea has been subjected to compression since the middle Miocene, we interpret that these normal faults were created during continental rifting in late Oligocene to early Miocene times. We suggest that the current ENE direction of maximum principal compressive stress observed in and around the Korean peninsula associated with the motion of the Amurian Plate induces the faults in the Hupo Basin to have reverse and right-lateral, strike-slip motion, when reactivated. A recent earthquake positioned on the Hupo Fault indicates that in the study area and possibly further in the eastern Korean margin, earthquakes would occur on the faults created during continental rifting in the Tertiary.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2004.04a
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• pp.33-38
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• 2004

The ocean loading displacement of the crust is one of the major error sources in space geodesy techniques. In the western part of the Korean Peninsula, the vertical displacement due to ocean loading reaches up to 3cm. To check out the possibility of correcting the inaccurate ocean tide model in the Yellow Sea, we used four GPS sites to compute the height variations and compared them with the model-predicted ones. The comparison shows relatively good agreement except for small differences in the phase and amplitude.

• 한국지구물리탐사학회:학술대회논문집
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• 2004.06a
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• pp.54-62
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• 2004

According to the Korea Tectonic Map, the Korean Peninsula can be divided into seven tectonic units and each of them shows a peculiar deformation pattern. In order to estimate an amount of crustal deformation in the Korean peninsula, we obtained the velocity vector fields of South Korea by dealing with the data set of the years 2001 and 2002, measured from the permanent GPS stations across the country To obtain a relatively precise coordinate of each station, we used GAMIT that is a comprehensive GPS analysis package developed at MIT, Then, a Kalman filter called GLOBK is used to combine the results from GAMIT and to estimate the relative velocity vector for the crustal deformations. The crustal movement of South Korea is turned out to be about 1mm per year westward and about 0.6mm per year southward. In case of Suwon and Seosan(Gyeonggi Massif), the movement occurs slightly to the north-east direction. The movement of a relative velocity field in the tectonic unit is unidirectional, yet the magnitude of the velocity is very small.

• Korean Journal of Remote Sensing
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• v.17 no.3
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• pp.231-242
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• 2001

In 2-pass differential SAR interferometry(DInSAR), the topographic phase signature can be removed by using a digital elevation model(DEM) to isolate the contribution of deformation from interferometric phase. This method has an advantage of no unwrapping process, but applicability is limited by precision of the DEM used. The residual phase in 2-pass differential interferogram accounts for error of DEM used in the processing provided that no actual deformation exits. The objective of this paper is a preliminary study to improve DEM precision using low precision DEM and 2-pass DInSAR technique, and we applied the 2-pass DInSAR technique to Asan area. ERS-1/2 tandem complex images and DTED level 0 DEM were used for DInSAR, and the precision of resulting DEM was estimated by a 1:25,000 digital map. The input DEM can be improved by simply adding the DInSAR output to the original low precision DEM. The absolute altitude error of the improved DEM is 9.7m, which is about the half to that of the original DTED level 0 data. And absolute altitude error of the improved DEM is better than that from InSAR technique, 15.8m. This approach has an advantage over the InSAR technique in efficiently reducing layover effects over steep slope region. This study demonstrates that 2-pass DInSAR can also be used to improve DEM precision.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.12
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• pp.7424-7429
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• 2014

GPS (Global Positioning System) is currently used widely in the ground section, such as surveying, mapping, geodesy, geophysics, the aviation section, such as aerial navigation and aerial photography, the sea section, including ship navigation and bathymetry, and space section, such as the satellite orbit and Earth's orbit. On the other hand, its use is limited due to the professional knowledge and expense to process the data for precise analysis. As a result, a web-based data processing solution for precise point positioning using GPS data was developed by c# for non-specialized people to process easily. In addition, the crustal movement speed of Korea after an earthquake was calculated to be an average of 30mm/year for each CORS, suggesting that it is possible to monitor crustal movement.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.28 no.2
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• pp.289-295
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• 2010

Yangsan fault system is a large fault more than 170km and one of the important structures Geologically that has been create recently in the Korean Peninsula. Debates have been made incessantly and widely throughout the Yangsan fault system because it's a lot of earthquake record. In this study, GPS data that was received from Yangsan GPS station in were processed by the Precise Point Positioning and the movement velocity was calculated by the statistical process about the results, where is the fault zone. The results showed that Yangsan is moving by azimuth angle of $126^{\circ}$ and the velocity of 49mm/year. It is respected that this results will be utilized in basic data about geophysics.

• Journal of the Korean earth science society
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• v.32 no.6
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• pp.640-653
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• 2011

We simulate the propagation of earthquake waves in the continental margin of Antarctica using the elastic wave modeling algorithm, which is modified to be suitable for acoustic-elastic coupled media and earthquake source. To simulate the various types of earthquake source, the staggered-grid finite-difference method, which is composed of velocity-stress formulae, can be more appropriate to use than the conventional, displacement-based, finite-difference method. We simulate the elastic wave propagation generated by earthquakes combining 3D staggered-grid finite-difference algorithm composed of displacement-velocity-stress formulae with double couple mechanisms for earthquake source. Through numerical tests for left-lateral strike-slip fault, normal fault and reverse fault, we could confirm that the first arrival of P waves at the surface is in a good agreement with the theoretically-predicted results based on the focal mechanism of an earthquake. Numerical results for a model made after the subduction zone in the continental margin of Antarctica showed that earthquake waves, generated by the reverse fault and propagating through the continental crust, the oceanic crust and the ocean, are accurately described.

• Journal of Astronomy and Space Sciences
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• v.26 no.4
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• pp.511-520
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• 2009

In this study, the Ocean Tide Loading (OTL) constituents were detected by the Precise Point Positioning (PPP) technique using GPS. Then, the GPS estimates of OTL constituents were compared with the predictions of the ocean tide models. We picked three permanent GPS stations as test sites and they are ICNW, SEOS, and CJUN. To detect the OTL constituents using GPS, we created vertical coordinate time series at 10-minute intervals using the PPP approach implemented in the GIPSY software. Through the tidal harmonic analysis of this height time series, the four major constituents ($M_2$, $S_2$, $K_1$, $O_1$) were determined. The amplitude obtained from the GPS height time series of the OTL constituents showed best match with the model predictions at CJUN, while the phase showed closest match at ICNW. The amplitude accuracy of the $M_2$, which is the dominant factor out of the 11 major constituents, was 24.8% on average.