• Economic and Environmental Geology
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• v.34 no.6
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• pp.649-652
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• 2001

• Earthquakes and Structures
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• v.8 no.1
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• pp.185-204
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• 2015

This study investigates the impact of the earthquake incident angle on the structural demand and the influence of ground motion selection and scaling methods on seismic directionality effects. The structural demand produced by Non-Linear Time-History Analyses (NLTHA) varies with the seismic input incidence angle. The seismic directionality effects are evaluated by subjecting four three-dimensional reinforced concrete structures to different scaled and un-scaled records oriented along nine incidence angles, whose values range between 0 and 180 degrees, with an increment of 22.5 degrees. The results show that NLTHAs performed applying the ground motion records along the principal axes underestimate the structural demand prediction, especially when plan-irregular structures are analyzed. The ground motion records generate the highest demand when applied along the lowest strength structural direction and a high energy content of the records increases the structural demand corresponding to this direction. The seismic directionality impact on structural demand is particularly important for irregular buildings subjected to un-scaled accelerograms. However, the orientation effects are much lower if spectrum-compatible combinations of scaled records are used. In both cases, irregular structures should be analyzed first with pushover analyses in order to identify the weaker structural directions and then with NLTHAs for different incidence angles.

• 한국전자현미경학회:학술대회논문집
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• 1996.05a
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• pp.59-62
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• 1996

• Economic and Environmental Geology
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• v.55 no.6
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• pp.597-616
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• 2022

The Chungnam basin is a crucial area for studying the Mesozoic crustal evolutionary history of the Korean Peninsula. This study reports the revised geology and new isotopic ages from the northeastern Chungnam Basin based on detailed geological mapping and LA-ICP-MS zircon U-Pb analysis. Our renewed geologic map defines intra-basin, basin-bounding, and basement fault systems closely related to hydrothermal gold-bearing quartz vein injections. Here, we propose the directions of (micro)structural and geochronological future work to address issues on the relationship between the tectonic process, basin evolution, and hydrothermal fluid migration in the southwestern Korean Peninsula.

• Economic and Environmental Geology
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• v.57 no.1
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• pp.41-50
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• 2024

This study reports the structural geometry and folding mechanism of a regional-scale overturned fold in the Daecheong Island, central-western part of the Korean Peninsula. Based on low-hemisphere stereographic and down-plunge projections using data from a detailed field survey, we classify the regional-scale fold as an open overturned fold shallowly plunging toward NE. The asymmetric and symmetric parasitic folds in the limb and hinge zones indicate layer-parallel shortening prior to flexural-flow folding. Fold dating must be required to decipher the orogenic process causing the regional-scale overturned fold in the Daecheong Island.

• Economic and Environmental Geology
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• v.27 no.3
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• pp.313-321
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• 1994

Structural interpretation by using subsurface attitude of coal seam and outcrop patterns of folds and faults shows that wrench and thrust tectonics took place simultaneously in the study area. From the interference patterns of fold axes, three generations of folding are suggested: $F_1$ (NE-SW), $F_2$ (N-S), and $F_3$ (E-W). Differential displacement of rock mass from north to south yields to E-W fold and Osypcheon Fault. Geometry of subsurface coal seam show different patterns comparing to those of surface outcrop because of shallow-depth crustal shortening which took place post Cretaceous.

• Proceedings of the KSEEG Conference
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• 2007.04a
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• pp.327-330
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• 2007

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• Economic and Environmental Geology
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• v.53 no.5
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• pp.631-643
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• 2020

The central-western Korean Peninsula contains records of an Early Mesozoic collisional event related to the final amalgamation of the East Asian continent. Here, we present a renewed geologic map of the Deokjeok and Soya islands in the central-western Korean Peninsula and its explanatory note. Our geologic map was based on a detailed investigation of the northeastern area of both islands, which is characterized by a complex fault and shear zone system that accommodated the crustal deformation related to the Mesozoic post-collisional orogenic collapse and the subsequent structural inversion. We suggest future directions of study aiming at addressing issues regarding the deformational responses of crust to the Mesozoic tectonic transition and orogenic cycles.

• Economic and Environmental Geology
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• v.23 no.2
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• pp.215-219
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• 1990

Geological and electrical resistivity surveys along the survey line of about 3 km between Kyungsangbukdo Youngilgun Hodong and Gwangmyungdong using by dipole-dipole electrode array method were carried out to examine the boundary and structural relationship between Tertiary Pohang and Janggi basins. Electrical resistivity data were interpreted qualitatively and quantitatively by means of pseudosection of apparent electrical resitivity distribution and finite difference method for two dimensional geologic structure model. The nearly vertical fault zone with low electrical resistivity value of 1-5 Ohm-m and widths of about 200m at the surface and 400 m at depth exists around 1.2 km west of national road between Ocheoneup and Yangbukmyun. Mudrocks, sandstones and tuffaceous rocks are widely distributed with electrical resistivity values of 6-77 Ohm-m. Especially, tuffaceous rocks with relatively high electrical resistivity value are predominant at eastern side of fault zone. Consequently, it is known that Pohang and Janggi basins are in fault contact.

• Economic and Environmental Geology
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• v.35 no.4
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• pp.373-378
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• 2002

Among the science and engineering fields in North Korean Academy of Sciences, geology occupies about 10 percent of the total number of departments. An analysis of major geologic research fields in North Korea, based on the number of authors of 2000-200l publications in a representative journal "Geology and Geography", shows the proportions as follows: mineralogy and petrology (31.0%), stratigraphy and paleontology (12.3%), economic geology and geochemistry (11.6%), geophysics and structural geology (14.2%), and applied geology (31.0%). This proportion is similar to that in South Korea in 1960s and shows that geologic research activity in North Korea is concentrated for the purpose of mineral resources exploration. The academic collaboration between South and North Korea in near future should include the researches on the reconstruction of geologic history in Korean peninsula and Northeast Asia and the environmental restoration from mining-related environmental pollution in North Korea. For active academic interchange between South and North Korea, efforts to overcome the academic gap are requisite. Frequent joint symposia, interchange programme of post-doctoral fellows, and cooperative researches on specific topics are recommended for this effort.