• Journal of the Korean Geophysical Society
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• v.2 no.3
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• pp.169-178
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• 1999

Low-field anisotropy of magnetic susceptibility (AMS) was measured with 247 samples from 17 sites of Pre-Cambrian anorthositic rocks in the Hadong-Sanchong area, southwestern part of the Ryongnam Block. Tectonic stress-direction is defined by the minimum susceptibility (k3) direction, and flow-direction by the maximum susceptibility (k1) direction. Five sites rendered self-consistent NW-SE site-mean tectonic stress-direction. Even though a general fold test for every site was not possible due to the homoclinal nature of the bedding attitudes, a site with various bedding attitudes shows far better clustering of the k3-direction before the bedding-tilt correction. The in-situ NW-SE tectonic stress-direction is consistent over the study area and compatible with petrographic foliation observed in metamorphic rocks in and arround the study area, suggesting a regional compressive force acted after the emplacement of the anorthositic rocks. On the other hand, flow-directions obtained from six sites varies from site to site. Strong-field IRM experiments show predominance of titanomagnetites over a small amount of hematite in some samples.

• Journal of the Korean Geophysical Society
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• v.9 no.3
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• pp.273-286
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• 2006

The Kyongsang Basin is the most representative Cretaceous basin in the Korean Peninsula where extensive crustal deformation and non-marine sedimentation took place in the early Cretaceous period. The lithology of the basement of the basin and adjacent areas is comprised of mainly Precambrian gneiss complex and Mesozoic granite intrusions. We have carried out magnetotelluric (MT) surveys to investigate the deep geoelectric structure around the Kyongsang Basin. The MT data were collected in the frequency range from 0.00042 to 320 Hz at 24 sites along a profile across the northern part of Kyongsang Basin. The results of MT inversion show that the thickness of sediments is estimated about 3 km to 9 km and the depth to base of granite intrusion is about 20 km. A remarkable discovery in this study is the highly conductive layer beneath the basin, having the resistivity of 1 ohm-m to 30 ohm-m and the thickness of about 3 km to 4 km or more. Although we are not able to reveal the nature of this layer, the result of this study could provide some basic information with respect to the formation process and deposit environment of the proto-Kyongsang Basin.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.389-396
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• 2002

In XXI century it is necessary to expect the recommencement and development of activities on mastering the Moon. In the long term it is construction of manned lunar bases with industrial, astrophysical, procuring, repair equipment and services. Interplanetary flights from the Moon demand smaller power expenditures, than from the Earth, therefore it is favourable to use its surface for the construction of space-vehicle launching sites. Flights of devices in libration points in the system 'Earth - Moon' are considered. Experience of engineering system creation for the Moon displays the great complexity in provision of serviceability and reliability of friction units. Open friction units should operate under following conditions on the Moon: pressure of environment (vacuum) $p\;>10\;^{-10}$ Pa; wide range of temperature change $+150^{\circ}C\;...170^{\circ}C$; high evaporability of lubricants; influence of temperature gradients and warping of constructions; sublimation of elements of constructional materials; irradiation of different physical nature; effect of micrometeorites; reduced gravitation; influence of abrasive particles of lunar ground; requirements on minimization of size and weight characteristics of a construction (high tension); undesirability (impossibility) of application of liquid and plastic lubricants; vibration, shock, acoustic loadings during start and landings to the Earth; difficulties in repair-regenerative operations in conditions of the Moon etc. Adhesive interaction of conjugated surfaces is the principal reason of possible failures of rubbed units on the Moon. In the research of the Moon automatic interplanetary stations of 'Luna' (USSR), 'Surveyer', 'Apollo' (USA) series were used. Stations executed functions of flying, landing, artificial satellites of the Moon, moon-rovers and manned spacecrafts such as 'Apollo'. The experimental- theoretical researches carried out in the sixtieth years on tribology for conditions of the Moon appeared to be rather useful to engineering of an outer space exploration and the decision of complex problems for the friction units operating in extreme conditions on the Earth. For the creation of highly loaded friction units for the long service life on the Moon it is required not only to use accumulated experience and designed technologies, but also to carry out wide scientific research.

• Economic and Environmental Geology
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• v.54 no.2
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• pp.177-186
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• 2021

For disaster management and mitigation of earthquakes in Korea Peninsula, active fault investigation has been conducted for the past 5 years. In particular, investigation of sediment-covered active faults integrates geomorphological analysis on airborne LiDAR data, surface geological survey, and geophysical exploration, and unearths subsurface active faults by trench survey. However, the fault traces revealed by trench surveys are only available for investigation during a limited time and restored to the previous condition. Thus, the geological data describing the fault trench sites remain as the qualitative data in terms of research articles and reports. To extend the limitations due to temporal nature of geological studies, we utilized a terrestrial LiDAR to produce 3D point clouds for the fault trench sites and restored them in a digital space. The terrestrial LiDAR scanning was conducted at two trench sites located near the Yangsan Fault and acquired amplitude and reflectance from the surveyed area as well as color information by combining photogrammetry with the LiDAR system. The scanned data were merged to form the 3D point clouds having the average geometric error of 0.003 m, which exhibited the sufficient accuracy to restore the details of the surveyed trench sites. However, we found more post-processing on the scanned data would be necessary because the amplitudes and reflectances of the point clouds varied depending on the scan positions and the colors of the trench surfaces were captured differently depending on the light exposures available at the time. Such point clouds are pretty large in size and visualized through a limited set of softwares, which limits data sharing among researchers. As an alternative, we suggested Potree, an open-source web-based platform, to visualize the point clouds of the trench sites. In this study, as a result, we identified that terrestrial LiDAR data can be practical to increase reproducibility of geological field studies and easily accessible by researchers and students in Earth Sciences.

• Journal of the Korean Geophysical Society
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• v.3 no.1
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• pp.1-12
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• 2000

A palaeomagnetic study was carried out on Early through Late Cretaceous sandstones and volcanic sequences (the Songnaedong Formation, Chaeyaksan Volcanics, Konchonri Formation, and Jusasan Andesite it ascending order) from Konchonri area in the northern Milyang subbasin of the Kyongsang Basin, Korea. A high-temperature stable remanence with direction of $d=22.9^{\circ},\;i=59.1^{\circ}\;({\alpha}_{95}=3.0^{\circ})$ has been isolated and a corresponding pole was $71.6^{\circ}N,\;199.6^{\circ}E\;(A_{95}=4.2^{\circ})$. The characteristic high-temperature component resides in both hematite and magnetite. The primary nature of this remanence is confirmed from positive fold and reversals tests, The palaeopole is consistent with those of the Hayang Group in other parts of the Kyongsang Basin. A comparison of the palaeomagnetic pole position from the studied area with the contemporary pole from China west of the Tan-Lu fault presents that Konchonri area has experienced little latitudinal displacement nor vertical-axis block rotation relative to the Chinese blocks since the Cretaceous. Based on the formations indicating dual polarity, radiometric and paleontologic data, the magnetostratigraphic age of the studied sequence from the Songnedong Formation to the Jusasan Andesite ranges from upper Albian to lower Campanian reverse polarity chronozone. On the other hand, volcanic samples of the Chaeyaksan Volcanics and the Jusasan Andesite showed the scattered directions considered in group, even though individual sample showed a stable remanent magnetization in response to thermal demagnetization. It indicates that they have been reworked after acquisition of the stable remanent magnetization.