• Proceedings of the KSEEG Conference
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• 2005.04a
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• pp.309-313
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• 2005

• Proceedings of the KSRS Conference
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• 2000.04a
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• pp.55-60
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• 2000

인공위성의 Radar Altimeter 자료를 통해 국지적인 중력이상을 조사하기 위하여 ERS-1 Altimeter를 이용하였다. ERS-1 Radar Altimeter는 조밀하게 인접한 데이터 간격(~8km)을 갖고 있어서 전지구적 규모뿐만 아니라 국지적인 연구에도 적합하다. 연구대상지역은 세 개의 판이 만나서 지진과 화산활동이 활발하게 진행되는 필리핀판 지역(동경1$10^{\circ}$~150$^{\circ}$, 북위 0$^{\circ}$~30$^{\circ}$)을 선정하였다. 이 지역에 대한 해저의 지형과 중력 이상 분석을 통해 판구조 운동의 여러 증거를 파악할 수 있다. ERS-1 Radar Altimeter를 통해 얻어진 지오이드 높이(Geoid geight)는 후리-에어 중력이상(Free-air gravity anomaly)으로 쉽게 전환시킬 수 있다. 본 연구에서는 Fast Fourier Transform(FFT)을 이용하여 지오이드기복을 직접 후리-에어 중력이상으로 전환시키는 Direct conversion method를 사용하였다. 후리-에어 중력이상은 지각평형과 직접적으로 연관되어 지각보상의 정도를 파악할 수 있게 하며 일반적으로 해양의 분지는 지각평형상태로 있어서 평균적인 중력이상은 0mgal 근처로 나타난다. 그러나 본 연구에서 살펴본 국지적인 후리-에어 중력이상은 판구조론과 관련한 해구난 호상열도에서는 해양분지에서의 평균적인 값과 다른 중력이상의 양상을 나타내었다.

• Journal of the Korean Home Economics Association
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• v.36 no.11
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• pp.193-207
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• 1998

이 연구의 목적은 아동의 연령과 성에 따른 아동의 역량지각 발달의 경향을 조사하고, 연령, 성을 포함한 가정환경과 또래 환경의 변수들의 역량지각에 미치는 영향을 구조평형 모델을 통해 알아 보았다. 또한, 이러한 역량지각의 발달 성향을 서구 문화권과 비교하여, 역량지각발달의 문화적 보편성이나 차이점을 알아 보고자 하였다. 유아, 또는 초등학교 저학년 아동은 면접으로, 그리고 3학년이상은 설문지를 사용하였다. 조사 대상은 유아, 초등학교 1, 3, 5학년, 중학교 1학년 아동 750명과 그들의 어머니이다. 인지, 사회, 신체 영역에서 모두 역량지각은 연령이 증가할수록 낮아졌다. 인지, 신체 영역의 역량지각에선 연령과 성의 상호작용효과가 나타났다. 그러나, 서구 문화권의 연구에서는 이러한 상호작용이 발견되지 않는다. 역량지각의 공변량구조모형에서는 또래환경 변수가 모두 포함시키기에 부적합한 변수로 나타났고, 연령, 성과 가족의 수입, 아버지의 교육수준, 가정의 물리적 환경, 부모의 정서적 지지가 아동의 역량지각에 의미 있게 영향을 미치는 것으로 나타났다.

• Journal of the Korean Geophysical Society
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• v.5 no.4
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• pp.293-303
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• 2002

Applying elastic plate model, we estimated elastic thickness and rigidity of the lithosphere in southern part of the Korean Peninsula($332km{\times}332km$ area of which center is $36.5^{\circ}N$ in latitude and $127.5^{\circ}E$ in longitude) by analysing terrain data and gravity data measured up to 2002. We tried to exclude the East Sea in choosing the study area because it has different tectonic environment. The mean Moho depth was estimated to be 30 km by power spectrum analysis of gravity data in the study area, Assuming one layer crust and applying elastic plate model, the loads with wavelengths of greater than 300 km are locally compensated, loads with wavelengths in the range 80-300km are partially supported by the strength of the lithosphere, and loads with wavelengths of less than 80km are almost completely supported by lithospheric strength. Assuming crustal model and rigidity, we calculated predicted coherence and compared it with observed coherence. As a result, we wert able to estimate the effective elastic thickness to be of 15 km(corresponding flexural rigidity is $3.0{\times}10^{22}Nm$). This indicates that the crust of the study area is relatively weaker than other old and stable continental regions but is similar to continental margins or oceanic area. The low rigidity could be explained by many tectonic and thermal activities such as orogenic activities, magmatic intrusions, volcanic activities, foldings, faultings, etc.

• Economic and Environmental Geology
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• v.18 no.4
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• pp.309-320
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• 1985

The crustal structure of the southern part of the Korean peninsula has been investigated based on the results of processing and anlaysis of gravity data. The processing techniques involve i) seperation of regional and residual anomalies by polynomial fittings, ii) power spectral analyses to determine the mean depth to the crustal base, iii) a filtering operation called "high-cut filtering and resampling," and iv) downward continuation to determine the undulation of the crustal base. The Bouguer anomalies show a lineation in the NE-SW direction which is the same as that of most mountains and tectonic lines of this area. The mean crustal depth is found to be 34km. The depth of the crustal base is varying in the estimated range of 26km to 36km with a thinner crust below the east coast than that of the west coast. The relief of the crustal base is appeared to be correlated with the regional surface topography. The linear regression relations computed between elevations and gravity anomalies indicate that the crust of this area seems to be not in perfect isostatic equilibrium but a little undercompensated state.

• Geophysics and Geophysical Exploration
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• v.22 no.1
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• pp.37-43
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• 2019

We present gravity anomaly maps based on KIGAM's gravity data measured from 2000 to 2018. Until 2016, we acquired gravity data on about 6,400 points for the purpose of regional mapping covering the whole country with data density of at least one point per $4km{\times}4km$ for reducing the time of the data acquisition. In addition, we have performed local gravity surveys for the purpose of mining development in and around the NMC Moland Mine at Jecheon in 2013 and in the Taebaeksan mineralized zone from 2015 to 2018 with data interval of several hundred meters to 2 km. Meanwhile, we carried out precise gravity explorations with data interval of about 250 m on and around epicenter areas of Gyeongju and Pohang earthquakes of relatively large magnitude which occurred in 2016 and in 2017, respectively. Thus we acquired in total about 9,600 points data as the result. We also used additional data acquired by Pusan National University for some local areas. Finally, gravity data more than 16,000 points except for the repetition and temporal control points were available to calculate free-air, Bouguer, and isostatic gravity anomalies. Therefore, the presented anomaly maps are most advanced in spatial distribution and the number of used data so far in Korea.

• Economic and Environmental Geology
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• v.44 no.6
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• pp.493-502
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• 2011

We study the deep structure of Korean Peninsula by estimating Moho depth and crustal thickness from using land and oceanic topography and free-air gravity anomaly data. Based on Airy-Heiskanen isostatic hypothesis, the correlated components between the terrain gravity effects and free-air gravity anomalies by wavenumber correlation analysis(WCA) are extracted to estimate the gravity effects that will be resulted from isostatic compensation for the area. With the resulting compensated gravity estimates, Moho depth that is a subsurface between the crust and mantle is estimated by the inversion in an iterative method with the constraints of 20 seismic depth estimates by the receiver function analysis, to minimize the uncertainty of non-uniqueness. Consequently, the average of the resulting crustal thickness estimate of Korean Peninsula is 32.15 km and the standard deviation is 3.12 km. Moho depth of South Korea estimated from this study is compared with the ones from the previous studies, showing they are approximately consistent. And the aspects of Moho undulation from the respective study are in common deep along Taebaek Mountains and Sobaek Mountains and low depth in Gyeongsang Basin relatively. Also, it is discussed that the terrain decorrelated free-air gravity anomalies inferring from the intracrustal characteristics of the crust are compared to the heat flow distributions of South Korea. The low-frequency components of terrain decorrelated Free-air gravity anomalies are highly correlated with the heat flow data, especially in the area of Gyeongsang basin where high heat flow causes to decrease the density of the rocks in the lower crust resulting in lowering the Moho depth by compensation. This result confirms that the high heat sources in this area coming from the upper mantle by Kim et al. (2008).

• 한국지구물리탐사학회:학술대회논문집
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• 2005.05a
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• pp.255-260
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• 2005

A Gravity characteristic of Svalbard archipelago in Arctic was studied by using ArcGP data. There are situated the Dasan science station. After bouguer correction, an edge effect of free-air anomaly, which is similar to topography, are not shown at passive continent margin, and after terrain correction with GTOPO30 data, gravity anomaly increases from continent to marine. that is deep connected with rise of Moho discontinuity. The correlation of topography and free-air anomaly shows that the isostasy of continent attains a little less than marine. After filtering, the residual anomaly are shown high and low anomalies related to fracture zone in continent and base depression or thick sedimentary layer in continental slope, marine.

• Economic and Environmental Geology
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• v.33 no.6
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• pp.537-545
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• 2000

Shipborne gravity data are analyzed to investigate crustal structure under Dok Island and its surrounding seamounts located in border of Ulleung Basin and Oki Bank in the East Sea. Relatively low free-air gravity anomaly compared with the volume of seamounts may be explainable by isostatic compensation. From 1 st to 3rd Dokdo Seamounts, the decrease of free-air and Bouguer gravity anomalies implies the different degree of isostatic compensation, crustal thickness or/and density contrast. 3-D gravity modelling shows that seamounts have the mirror roots for regional Airy isostatic compensation, and from Ulleung Basin to Oki Bank, Moho discontinuity deepens and the density of crust is decreases. The results infer that study area is transitional zone from thin oceanic to thick continental crust. The depth of Moho discontinuity is about 15∼16 km, which may be interpreted as an uplifting of Mantle to shallow depth comparing with other borders of the Ulleung Basin.

• Economic and Environmental Geology
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• v.40 no.2 s.183
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• pp.153-170
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• 2007

Loading time and loading environment of the Dokdo seamounts were studied from flexure model and VGP(Virtual Geomagnetic Pole) determined by gravity and magnetic data. In spite of their similarity in size. a large difference about 50 mGal between gravity anomaly peaks of Dokdo and the Isabu Tablemount suggests different compensation degrees. Flexural modeling results show that the flexural rigidity(effective elastic thickness) of lithosphere for Dokdo is stronger(thicker) than that for the Isabu Tablemount. Also, it implies that the age of lithosphere at the time of loading of the Isabu Tablemount may be younger than that of Dokdo. Magnetic anomalies occur complicated over the Dokdo seamounts. Paleomagnetism was studied from VGP estimated by the least square and the seminorm magnetization methods with 1500 m upward continued magnetic anomalies. Age dating of Dokdo from previous study, flexural modeling, VGP, and geomagnetic polarity time scale suggest that after the cease of spreading in the Ulleung Basin, the Isabu Tablemount was formed first in normal polarity interval and followed by Dokdo. Also, they indicate that the fist large eruption of Dokdo was in normal polarity interval and the second large eruption in reversed polarity interval. The Simheungtaek Tablemount was formed in normal polarity interval between the formations of the Isabu Tablemount and Dokdo. These loading times for the Dokdo seamounts show a good coherence with the compressive stress period after the end of the opening of the East Sea. The Dokdo seamounts probably was caused by volcanism associated with the compressive stress.