• 한국지구과학회:학술대회논문집
• /
• 2010.04a
• /
• pp.124-127
• /
• 2010

본 연구에서는 통가 해역 라우분지의 열수 광상 가능성이 있는 해산들에 대하여 자력탐사가 수행되었다. 그 중 TA 09 해산에 대하여 심해견인 자력탐사가 실시되었으며 심해견인 자력탐사는 정밀한 탐사를 위하여 해저면에서 약 50 ~ 60 m 고도를 유지하며 자력계를 견인하였다. 탐사지역의 총 자력 성분은 Overhauser Proton Magnetomer (모델 SeaSPY 300(해상자력계)m, SeaSPY 6000(심해견인자력계))를 이용하여 측정되었다. 탐사 해산들 중 해상자력탐사와 심해자력탐사가 같이 수행된 TA 09 해산과 주요 열수 광상 유망 지역으로 분류되는 TA 12, 26 해산에 대해서만 측정된 지자기값을 이용하여 자기이상도를 구하였으며 자화역산법을 이용하여 자화이상도를 제작하고 분석하였다. TA 09 해산과 TA 26 해산에서의 해상 자기이상도는 쌍극자 이상형태의 단순이상을 보이며 TA 12 해산에서는 정상부에 고이상이 나타나고 그 주변으로는 저이상대가 분포하고 있다. TA 09 해산에서의 해상자력계에 의한 자기이상치와 심해견인자력계에 의한 자기이상치를 비교하여 보면 거의 10배 이상의 해상도 차이를 보여준다. 연구지역 탐사해산들의 해저지형과 비교하여 보면 열수분출대의 가능성이 높은 저자화이상대들은 주로 해산의 정상부 및 정상부 칼데라와 그 칼데라 주변부에 주로 위치하고 있는 모습을 나타내고 있다. 향후 타 탐사 해산들에 대한 자기이상에 대한 정밀처리/분석 후 탄성파 탐사결과, 암석샘플의 결과 및 지화학결과 등과 비교하여 열수광상의 존재 여부 및 위치 추정 분석이 필요할 것으로 판단된다.

• Economic and Environmental Geology
• /
• v.54 no.1
• /
• pp.117-126
• /
• 2021

Satellite magnetic observations reflect the magnetic properties of deep crust about the depth of Curie isotherm that is a boundary where the magnetic nature of the rocks is disappeared, showing long wavelength anomalies that are not easily detected in near-surface data from airborne and shipborne surveys. For this reason, they are important not only in the analyses on such as plate reconstruction of tectonic boundaries and deep crustal structures, but in the studies of geothermal distribution in Antarctic and Greenland crust, related to global warming issue. It is a conventional method to compute the spherical harmonic coefficients from global coverage of satellite magnetic observations but it should be noted that inclusion of erroneous data from the equator and the poles where magnetic observations are highly disturbed might mislead the global model of the coefficients. Otherwise, the reduced anomaly model can be obtained with less corruption by choosing the area of interest with proper data processing to the area. In this study, I produced a satellite crustal magnetic anomaly map over East Asia (20° ~ 55°N, 108° ~ 150°E) centered on Korean Peninsula, from CHAMP satellite magnetic measurements about mean altitude of 280 km during the last year of the mission, and compared with the one from global crustal magnetic model (MF7). Also, a comparison was made with long wavelength anomalies from EMAG2 model compiled from all near-surface data over the globe.

• Journal of the Geological Society of Korea
• /
• v.54 no.6
• /
• pp.677-682
• /
• 2018

Magnetic anomalies are sensitive to magnetic properties present in deep Earth and near surface structures. Such geophysical characteristics often can be quantified by numerical analyses. In this study, we developed a finite element method (FEM) approach to compute magnetic anomalies using COMOL $Multiphysics^{(R)}$. This FEM approach was verified by comparing its numerical results with the previously known analytic solution for a uniformly magnetized sphere. Then, we used the method to compute magnetic reversal patterns near mid-ocean ridge with various faulting scenarios. This COMSOL-based approach can be incorporated into advanced multi-physical numerical models to understand the Earth.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2006.06a
• /
• pp.113-116
• /
• 2006

Successful field test results for detection of buried undersea HVDC by magnetic vector measurements are discussed. Further study will be focused on practical utilization.

• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.2
• /
• pp.137.2-137.2
• /
• 2012

위성이 우주에서 노출되는 우주방사선 환경은 위성의 임무궤도 및 임무 기간에 따라 크게 달라진다. 지구 주위의 자기장에 의해 갇혀있는 양성자 및 전자의 환경은 고도에 따라 밀도 및 분포의 차이를 보인다. 특히 밴 앨런 밸트 내의 경계부분을 넘어서는 높은 고도에서의 방사선 입자별 노출 환경은 저궤도의 환경과는 구성 및 영향성이 크게 다르다. 본 논문에서는 전자 밸트 고도에서 운영되는 정지궤도 위성의 우주방사선 입자 환경을 분석하였다. 지구 자기장에 갇힌 입자, 태양입자 및 외부은하 입자 환경을 모델별로 분석하였으며 각 입자별 Flux 및 Fluence 스펙트럼을 이용하여 총 이온화 조사량과 중이온 스펙트럼을 도출하였다.

• Geophysics and Geophysical Exploration
• /
• v.5 no.3
• /
• pp.157-168
• /
• 2002

Improved procedures were implemented in the production of the lithospheric magnetic anomaly map from Magsat satellite magnetometer data of East Asia between $90^{\circ}E-150^{\circ}E$ and $10^{\circ}S-50^{\circ}N$. Procedures included more effective selection of the do·it and dawn tracks, ring current correction, and separation of core field and external field effects. External field reductions included an ionospheric correction and pass-by-pass correlation analysis. Track-line noise effects were reduced by spectral reconstruction of the dusk and dawn data sets. The total field magnetic anomalies were differentially-reduced-to-the-pole to minimize distortion s between satellite magnetic anomalies and their geological sources caused by corefield variations over the study area. Aeromagnetic anomalies were correlated with Magsat magnetic anomalies at the satellite altitude to test the lithospheric veracity of anomalies in these two data sets. The aeromagnetic anomalies were low-pass filtered to eliminate high frequency components that may not be shown at the satellite altitude. Although the two maps have a low CC of 0.243, there are many features that are directly correlated (peak-to-peak and trough-to-trough). The low CC between the two maps was generated by the combination of directly- and inversely-correlative anomaly features between them. It is very difficult to discriminate directly, inversely, and nully correlative features in these two anomaly maps because features are complicatedly correlated due to the depth and superposition of the anomaly sources. In general, the lithospheric magnetic components were recovered successfully from satellite magnetometer observations and correlated well with aeromagnetic anomalies in the study area.

• Geophysics and Geophysical Exploration
• /
• v.27 no.2
• /
• pp.119-128
• /
• 2024

Marine magnetic surveys provide a rapid and cost-effective method for pioneer geophysical survey for many purposes. Sea-surface magnetometers offer high accuracy but are limited to measuring the scalar total magnetic field and require dedicated cruise missions. Shipboard three-component magnetometers, on the other hand, can collect vector three components and applicable to any cruise missions. However, correcting for the ship's magnetic field, particularly viscous magnetization, still remains a challenge. This study proposes a new additional correction method for ship's viscous magnetization effect in vector data acquired by shipboard three-component magnetometer. This method utilizes magnetic data collected simultaneously with a sea-surface magnetometer providing total magnetic field measurements. Our method significantly reduces deviations between the two datasets, resulting in corrected vector anomalies with errors as low as 7-25 nT. These tiny errors are possibly caused by the vector magnetic anomaly and its related viscous magnetization. This method is expected to significantly improve the accuracy of shipborne magnetic surveys by providing corrected vector components. This will enhance magnetic interpretations and might be useful for understanding plate tectonics, geological structures, hydrothermal deposits, and more.

• Economic and Environmental Geology
• /
• v.43 no.3
• /
• pp.249-258
• /
• 2010

In general, a crustal geomagnetic (or gravity) anomaly compiled at one altitude can be estimated at a different altitude by continuation using the Fourier transform (FT). However, in case of continuation with a great distance between the two elevations, or, in particular, in case of downward continuation, the estimated anomalies by the FT are likely to be mathematically unstable so that the estimated values are not realistic. To solve this problem, two independently measured magnetic field anomalies at different altitudes, such as aeromagnetic and satellite magnetic observations, are implemented to estimate values at in-between altitude for better understanding and interpreting geophysical and geological features. This ‘'dual continuation’' technique is straightforward in the FT and gives a more realistic estimate in all altitudes when we simulated with a set of prismatic bodies at different altitudes. This implies that we add up another constraint like satellite-based observations on the geopotential field modeling for the non-unique geological and geophysical problems to a conventional Fourier-type continuation technique with a single set of observations.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2009.10a
• /
• pp.107-109
• /
• 2009

Micromagnetism explores magnetic configurations in nano-scales to visualize the details of magnetic domain structures, and also can produce snapshots of complex remanence or other magnetic states. The particle shape has a profound effect on the magnetic hysteresis. For instance, octahedral magnetite showed higher coercivity and squareness than cubic magnetite.

• Geophysics and Geophysical Exploration
• /
• v.11 no.4
• /
• pp.343-349
• /
• 2008

We have constructed a car-borne magnetic exploration system, in which a car drags a non-magnetic cart on which a magnetometer is installed. In the total magnetic field measured as a vectorial sum in this system, are included the magnetic field generated by the car itself. This magnetic field, doing the role of a magnetic noise, should be eliminated. For this purpose, we have set up a measurement condition to get the same effect as if we have put the car in one point and thereafter measured the magnetic field around it. In this case, if there is any magnetically anomalous body in the area, we can consider all the remaining magnetic field to have been generated by the car itself, once the geomagnetic field eliminated. We tried to invert the magnetic field considered to have been generated by the car and succeeded to derive the magnetic moment and the direction of the induced and remanent magnetic field of the car respectively. Once the magnetic moment and the direction of the induced and remanent magnetic field have been calculated, the magnetic field generated by them in specific points can be directly and analytically calculated. This result can be used in the future to eliminate the magnetic field generated by the car itself doing the role of a magnetic noise during the procedure of reduction of the measured magnetic exploration data by the car-borne magnetic exploration system.