• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1070-1072
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• 2003

This study focuses on examing the feasibility of differential SAR interferometry (DInSAR) in the Northeastern Kyungsang Basin, Korea. Major faults in the Kyungsang Basin such as Yangsan fault, Dongrae fault, and Ulsan fault had developed during Cretaceous, and the activeness of these faults is still controversial in Korean geology community. We attempt to measure displacements in the study area by applying DInSAR techniques to JERS-1 SAR data sets. Some surface displacements are recognized by DInSAR method at Young-il Bay in which the POSCO Company locates, although the displacements may not be directly associated with geologic structures. We also discuss atmospheric effects for the techniques used.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.674-677
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• 2005

The characteristics of geothermal resources in Korea was roughly estimated using hot springs, 580 geothermal gradients and 338 heat flow data. In the aspect of hot springs with geologic structure, location of hot springs coincide with fault zone, especially younger age of Cretaceous to Tertiary. In the aspect of geothermal gradients, Pohang area shows the highest geothermal gradient anomaly, which is covered with unconsol idated rock of low thermal conductivity preserving the residual heat from igneous activity or radioactivity elements decay. In the aspect of heat flow density, high anomaly can be found along the zone connecting Uljin-Pohang-Busan on the southeastern part of Korean peninsula at which big fault zone as Yangsan fault is well developed.

• The Journal of Engineering Geology
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• v.8 no.1
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• pp.13-23
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• 1998

An intensity of the 1997 Kyungju earthquake(M=4.3) was estimated at three hundred locations based on the field survey and questionaires from 2200 residents. The isoseismal shows almost circular pattern which doesnot reflect some specific geological trends. However,most of the Kyeongsang basin except the southwestern part is included within the area of MM intensity V. There occurred strong shaking, numerous cracks on the wall of the houses, and movement of slate on the roofs, falling of the tiles from the monument. The isoseismal of the highest MM intensity VII, 1-3 km in width and 9 km in length, is elongated along the Yangsan fault, which is located about 1.5 km west from epicenter. The lineaments near the epicenter exhibit almost N-S and NNE directions. The lineament distribution, the pattern of damage area and the solution of fault plane suggest that the Kyongju earthquake occurred with strike-slip sense along the Yangsan fault. The calculated intensity attenuation(I) with distance(R) is as follows : $I{\;}={\;}I_o{\;}+{\;}0.3461{\;}-{\;}0.3274{\;}{\times}{\;}1nR{\;}-{\;}0.086{\;}{\times}{\;}R$.

• Journal of the Korean Geosynthetics Society
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• v.17 no.1
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• pp.139-152
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• 2018

This study is an analysis of slope failure examples of cut sedimentary hills during construction road in Kyoungsang Basin, especially Yangsan Fault system (Ilkwang-Dongrae fault). This area involved a lot of hillslope failures compared to other areas during road construction. The exposed failure slopes were first face-mapped, and then back analyzed based on the limit equilibrium method to assess the shear strength parameters of discontinuity (bedding). The results of this analysis indicate that the shear strength parameters of discontinuity (bedding) are significantly smaller than those used in the design stage and presented in the existing works. The filling in the bedding and emerging groundwater may be decreasing strength parameters. Especially, the clay in the bedding plays a key role in the effect of the shear strength. The study also suggests that the bedding angle and the internal friction angle are proportional to each other. Using this relationship and knowing the bedding angle, the friction can easily be estimated.

• Journal of the Korean Geophysical Society
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• v.3 no.4
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• pp.245-250
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• 2000

By using amplitude ratios (SV/P, SH/P, SV/SH) and P and S wave polarities, we obtained fault plane solutions of the June 26, 1997 Kyong-ju earthquake. The solutions show $150{\pm}4^{\circ}$ in strike, $63{\pm}6^{\circ}$ in dip and $65{\pm}7^{\circ}$ in rake, or $18{\pm}12^{\circ}$ in strike, $26{\pm}3^{\circ}$ in dip and $120{\pm}5^{\circ}$ in rake. This result implies the stress field trending ENE-WSW, which is remarkably consistent with the previous results obtained from the moment tensor inversion, and from the composite fault plane solution for the events occurred around the Yangsan fault area.

• Economic and Environmental Geology
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• v.54 no.3
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• pp.389-397
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• 2021

Moryang Fault is geomorphologically observed as a linear fault valley from Angang through Moryang, Duckhyun and Wondong to Gimhae, and contacts with Yangsan Fault, being obliquely away to the east, at Angang disrict. The fault valley appears a V-shape feature with a width from 100 to 300 m, and has fragmental zones of the fault along the valley on a small scale. Nine fault-outcrop localities were found along the nine-kilometers valley between Daehyun-ri, Gyeongju, and Baenaemi-gogae, Yangdong-ri, Ulsan. The fault strikes the North-North-East to the Northeast and dips to the Northwest with high angles, and reveals it had been undergone predominantly sinistral reverse fault movement sense, left-lateral and right-lateral strike-slip sense in bedrocks. However, after unconsolidated sediments, there was the top-up-to-the-east dextral reverse fault movement.

• The Journal of the Petrological Society of Korea
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• v.21 no.3
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• pp.335-365
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• 2012

Fission-track (FT) thermochronological records from SE Korean Cretaceous-Paleogene granitic plutons in different fault-bounded blocks reveal contrasting cooling and later thermal histories. Overall cooling patterns are represented by a monotonous (J-shaped) curve in most plutons except some Cretaceous granites retaining a complicated (N-shaped) path due to post-reset re-cooling. Discriminative cooling rates over different temperature ranges can be explained for individual plutons with respect to relative pluton sizes, differences in initial heat loss depending on country rocks, and the presence and proximity of later igneous activity. Even within a single batholith, cooling times for different isotherms were roughly contemporaneous with respect to positions. Insignificant deviations in cooling ages from two different plutons in succession across the Yangsan fault may suggest their contemporaneity before major horizontal fault movement. The extent of later thermal rise recorded locally along the Yangsan and Dongnae fault zones were reached the Apatite Partial Stability Zone ($70-125^{\circ}C$), but did not exceed $200^{\circ}C$. Thermal alteration from fractured zones in the Yangsan-Ulsan fault junction may suggest a thermal reset above $290^{\circ}C$ resulting a complete reset in FT sphene age (31 Ma), caused by a tectonic subsidence in Early Oligocene. A consistency in FT zircon/apatite ages (24 Ma) may imply a sudden rapid cooling over $200-105^{\circ}C$, plausibly related to the abrupt tectonic uplift of the Pohang-Gampo Block including the fault junction in Late Oligocene. A remarkable trend of lower cooling ages for $300-200-100^{\circ}C$ isotherms (i.e., 19% for FT sphene and K-Ar biotite; 20% for FT zircon; 27% for FT apatite) from the east of the Ulsan fault (Pohang-Gampo Block) comparing to the west of the fault may be attributed to retarded cooling times from the Paleogene granites and also reflected by their partially-reduced apatite ages due to later thermal effects.

• The Journal of Engineering Geology
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• v.26 no.4
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• pp.551-559
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• 2016

The chemical composition and noble gas isotopes of 10 deep groundwater samples were analyzed to know the circulation of groundwaters in the Yangsan fault and the Gampo fault. The chemical types of groundwaters show the $Ca-HCO_3$ type and $Ca-SO_4(Cl)$ type, and show indistinct relationship with geology. Noble gas isotopic data of most groundwaters were plotted along the air-crust mixing line on $^3He/^4He$ vs. $4^He/^{20}Ne$ diagram, and show dominant $^3He$ of air origin except one sample that shows helium mixing of crust origin. This indicates that groundwater actively circulates along fault, and fault could not play an role of upward pathway of a deep-seated helium gas. A comparatively high $^4He$ indicates that groundwater flows in an aquifer assuring relatively enough water-rock interaction.

• Journal of the Mineralogical Society of Korea
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• v.18 no.3 s.45
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• pp.165-181
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• 2005

The granitic rocks distributed in the southern part of the Yangsan Fault are classified into five distinct rock facies based on the field relation, petrography and geochemical characteristics. These five different rock facies can be grouped into two considering their origins. Group I, which reveals various evidences of magma mixing, includes three rock facies of granodiorite, enclave-rich porphyritic granite, and enclave-poor porphyritic granite. Group H intruding Croup I includes equigranular granite and micrographic granite with no evidence of magma mixing. It is suggested that the distinctively different trace element and isotopic chemistries between group I and II, support evolution from the different parental magma. It is suggested that the three rock facies in group I were generated by different degrees of magma mixing in addition to fractionation of plagioclase. MMEs experienced fractionation of biotite. The two facies in group H seem to have been generated from different parent magma from group I and evolved by fractionation of K-feldspar. The Rb-Sr whole-rock ages of the group I rocks yield $59.2\~58.9Ma$, and those of the group II rocks give 53. $3\~51.7Ma$, regardless of their distribution whether they occur in the eastern or western parts of the Yangsan Fault. Based on Sm-Nd isotope compositions, depleted mantle model ages $(T_2DM)$ of the group I range $0.8\~0.9Ga$, while those of the group II$0.6\~0.7Ga$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.133-143
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• 2018

Liquefaction is one of secondary damages after earthquake and has been rarely reported until earthquake except Mw = 5.4 15 November 2017 Pohang earthquake in Korea. In recent years, Mw = 5.8 12 September 2016 Gyeongju earthquake and Mw = 5.4 15 November 2017 Pohang earthquake, which induced liquefaction, occurred in fault zone of Yangsan City located at south-eastern part of Korea. This explains that Korea is not safe against liquefaction induced by earthquake. In this study, the distance between the centroid of administrative district and the epicenter located at Yangsan fault, peak ground velocity (PGA) induced by both Mw = 5.0 and 6.5, and liquefaction potential index (LPI), which is calculated by using groundwater level and standard penetration test results of 274 in the area of Gimhae city located in adjacent to Nakdong river and across Yangsan fault, have been estimated and then kriging method using geographical information systems has been used to evaluate liquefaction effects on the damage of facilities. This study presents that Mw = 5.0 earthquake induces a small and low level of liquefaction resulting in slight damage of facilities but Mw = 6.5 earthquake induces a large and high level of liquefaction resulting in severe damage of facilities.