• Proceedings of the KSRS Conference
• /
• v.1
• /
• pp.157-157
• /
• 2006

• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2011.06a
• /
• pp.244-244
• /
• 2011

• The Journal of Engineering Geology
• /
• v.28 no.4
• /
• pp.619-630
• /
• 2018

The purpose of this study is to investigate the existence of faults and intrusive rocks in the volcanic rock mass of Ulleung-do using magnetic anomalies. The magnetic survey data show that basaltic (mafic) rocks have high magnetic anomalies and that trachytic (felsic) rocks have low magnetic anomalies, implying that the anomaly distributions can be used to distinguish between different volcanic rock types that may be covered by regolith (such as alluvial and colluvial deposits) and other sedimentary layers. Our results show that basaltic rocks are not present within the Nari caldera. However, outside the caldera, the occurrence of high magnetic anomaly values of >$1,000{\gamma}$ is presumed to reflect the existence of basaltic craters or volcanic vents that formed prior to the eruption of the trachytic rocks. In particular, the area with anomaly values of >$1,000{\gamma}$ in the vicinity of Namyang-ri, southwest of Ulleung-do, is interpreted as having a high probability of hosting a crater and vent originating from mafic volcanism.

• Economic and Environmental Geology
• /
• v.14 no.2
• /
• pp.77-91
• /
• 1981

An airborne magnetometer survey was carried out over an offshore area of about $200,000km^2$ from the southeastern, southern and western part of Korea. Detailed magnetic studies on the geological structure of the southern part of above area ($100,000km^2$) was accomplished. Residual aeromagnetic map was made in order to delineate magnetic provinces, magnetic lineaments and sedimentary basins by application of least square method using computer system. To determine the depth of the sedimentary basins pseudo-gravimetric method was applied. 1. The area studied is divided into four magnetic provinces for the purpose of interpretation on the basis of the magnetic maps. 2. Near shore area and its attached islands of southern part (fiirst and second magnetic province) can be regarded as being the extension from the land geology due to presentation of strong magnetic anomalies and shallow magnetic basements. 3. Magnetic lineament 1-1 is strong magnetic anomalous region which is presumably relevant to volcanic activities in Cretaceous. The depth of magnetic basement of the lineament was determined to 1,500 m. Negative magnetic anomalous zones B1-1 and B1-2 which represent Tertiary basins showed depth of magnetic basement 3 km and 4 km each. The latter can be interpreted as extension of the Taiwan basin which is consisted of Tertiary sediments. 4. Magnetic lineament 2-1 coincide with Rainan-Fukien massif running NE-SW direction. A lineament located in central part of magnetic lineament 2-1 is well connected with extension of Sobacksan anticlinal axis on land. Volcanic rocks in Gyongsang system concentrated along this lineament. 5. The characteristics of magnetic pattern in the southern Yellow sea basin of western part of Jeju island show weaker magnetic anomalies and deeper magnetic basements than first and second magnetic provinces indicating geological structure of this basin seems to be quite different from that of Jeju strait. 6. In southern part of Jeju island, smoother magnetic pattern develope southward. Maximum depth of magnetic basement in sedimentary basins BIV-1 and BIV-2 were determined down to 6,000 m increasing its thickness toward Taiwan up to 11,000 m in the shelf area off Taichung, Taiwan. Judging from the fact that hydrocarbon was founded in the Tertiary sediments of western coastal area of Taiwan, it can be expected that hydrocarbon will be existed in these sedimentary basins of southern part of Jeju island.

• Economic and Environmental Geology
• /
• v.30 no.5
• /
• pp.451-458
• /
• 1997

The horizontal magnetic dipole as well as electrical dipole was adopted as a source to compute one-dimensional electromagnetic field behavior in controlled source magnetotellurics. he Cagniard impedances due to horizontal magnetic dipole source, especially phases, showed better frequency characteristics than those due to electric one. The magnetic dipole is inferior to the electric dipole in the point of relatively weak transmitting power at low frequency. But considering high resistivity charateristics of Korean geology, the magnetic dipole source is recommended for the survey up to depth of 500 m. A vector CSMT was introduced to get more reliable data in the area of two- or three-dimensional structures. A software and interpretation technique using polarization ellipses were developed. The technique was tested by synthetic data, which provided theoretical basis of the methodology. Although CSMT has inevitable limitation of investigation depth due to practically possible source-receiver separation, we proposed to use the technique developed in this paper where MT is not available, for example, in extremely noisy area or for shallow target.

• The Journal of Korean Obstetrics and Gynecology
• /
• v.19 no.2
• /
• pp.261-270
• /
• 2006

Purpose : The purpose of this study is to show the effect of acupuncture, moxibustion and magnetic innervation therapy for urinary incontinence symptoms. Methods : Ten female patients suffering from urinary incontinence had been given the treatments of acupuncture, moxibustion and magnetic innervation therapy for more than 8 times. Before and after treatment, they accomplished questionnaire for quality life survey and checked vaginal pressure measurement with perionometer. Results : The results were as follows 1) The mean${\pm}SD$ of Questionnaire score was significantly decreased from $35.40{\pm}11.88$ to $21.20{\pm}7.66$ after treatment(P<&0.047). 2) The mean${\pm}SD$ of maximum vaginal presssure was significantly increased from $48.80{\pm}25.35mmHg$ to $62.20{\pm}25.09mmHg$(p<&0.040). 3) The mean${\pm}SD$ of average vaginal presssure was significantly increased from $33.50{\pm}19.62mmHg$ to$43.10{\pm}16.49mmHg$(p<&0.015). Conclusion : Our results suggested that acupuncture, moxibustion and magnetic innervation therapy is effective for urinary incontinence symptoms.

• The Bulletin of The Korean Astronomical Society
• /
• v.45 no.1
• /
• pp.59.3-60
• /
• 2020

We present the results of polarization observations at submillimeter wavelengths towards Monoceros R2 (Mon R2). The polarized thermal dust emission was obtained from SCUBA-2/POL-2 at 450 ㎛ and 850 ㎛, simultaneously. This observation is a part of the JCMT BISTRO survey project. The polarization angle distributions at 450 ㎛ and 850 ㎛ are similar and the mean value of angle differences at two wavelengths is 5.5 degrees. The Mon R2 is one of massive star-forming regions containing a clear hub-filamentary structure. The hub region shows star formation activities, and surrounding filaments provide channels for matters to move into the hub region. It is not well known the role of magnetic fields in a hub-filamentary structure. Some studies have shown well-ordered polarization segments along a filamentary structure and magnetic field morphology traced by polarization segments is interpreted as to help gas flow along the filamentary structrue. Our observations shows that filaments in Mon R2 have spiral structure and the magnetic field lines are parallel to the filaments. We interpret that the spiral structure can be formed by a rotation hub-filament system with gas flowing along the filaments to the hub. We found several dust clumps at the central part of the hub region of the Mon R2. They seems to be formed at locations where spiral field lines meet each other. These results show one observational example that a magnetic field play a role in gas flow.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2003.11a
• /
• pp.410-415
• /
• 2003

Ground subsidence has occurred in the downtown of Muan-eup in Korea. Integrated geophysical survey, including two-dimensional resistivity, CSMT(Controlled source magnetotelluric), magnetic, borehole logging, GPR and resistivity tomography, has been conducted to investigate the cause of subsidence and ground conditions. Since the target area is in the city downtown, there were no spaces for surface geophysical methods. To get regional geology and to facilitate the detailed geophysical interpretation in the survey area, two-dimensional resistivity, CSMT and magnetic surveys have been applied in the outer region of the downtown. From these results, we could accurately define the Gwangju fault system and estimate the geologic conditions in the downtown. For the detailed survey of the downtown area, resistivity tomography and borehole logging data have been acquired using a few tens of densely located boreholes. Among these survey results, borehole logging data provided the guide to classification of the rock type and we could define the geologic boundary of granite and limestone formations. From the resistivity tomograms of 42 sections, which are densely located enough to be interpreted in a three-dimensional manner, we could delineate the possible weak zones or cavities in the limestone formations. In particular, resistivity tomograms in the subsided area showed the real image of ground subsidence. The map of hazardous zone has been derived from the joint interpretation of these survey results and we could provide the possible reinforcement strategy in this area.

• Journal of Korean Society of societal Security
• /
• v.1 no.4
• /
• pp.73-81
• /
• 2008

Electromagnetic induction surveys are one of the useful methods to detect the location and buried depth of underground utilities by measuring horizontal and vertical magnetic fields. It can effectively detects single buried utility with the accuracy of within 20 cm. However when another utility is buried near to target one, the accuracy of utility location considerably decreases due to the distortion of magnetic fields caused from adjacent utility. This study shows the ways to verify the location and buried depth of target utility when magnetic fields does not show symmetric distribution due to adjacent another utility. Using Bluetooth wireless communication tools, we developed the way to records measured magnetic fields to handheld PDA. We investigated the criteria for minimum distance of two adjacent utilities to separate the individual responses through field model test.

• Proceedings of the KIEE Conference
• /
• 1999.07e
• /
• pp.2368-2370
• /
• 1999

A nationwide survey for electric and magnetic fields(EMFs) near overhead transmission lines has been conducted. The median values of the electric and magnetic fields of 208 transmission lines were 0.50 kV/m and 12.6 mG, respectively. The maximum values were 3.16 kV/m and 125 mG. The measured EMFs were compared with the calculated ones. The causes of the discrepancy between measured and calculated EMFs are also discussed.