• Korean Journal of Remote Sensing
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• v.37 no.6_2
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• pp.1901-1922
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• 2021

Since most large earthquakes occur by reactivation of preexisting active faults, it is important to understand the locations and characteristics of active faults in terms of earthquake hazard research and earthquake disaster prevention. Recently, several remote sensing techniques are broadly used for lineament analysis performed prior to field surveys in active fault surveys. The aim of this paper is introducing simple principles and application examples of each remote sensing technique (satellite remote sensing, airborne remote sensing, InSAR, LiDAR) widely used for active fault investigation. This paper also explains the analytical methods for the slope break generated by fault activity based on GIS and the horizontal displacement of the strike-slip fault. In discussion, we would like to discuss the problems and solutions on making DEM based on aerial photography, and a new developed technique (RRIM) to overcome the problems of DEM based on aerial LiDAR. Understanding remote sensing techniques used for active fault investigation and utilizing appropriate methods depending on the situation and limitations of each remote sensing technique are important for effective active fault investigation.

• Journal of Convergence for Information Technology
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• v.8 no.6
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• pp.59-66
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• 2018

The utilized coefficient of friction (UCOF) as a ratio of the shear force to the normal force on the ground during walking is used to identify the point at which slip is likely to occur. Shoe walking will change the utilized coefficient of friction by shoe design such as sole thickness and hardness, heel shape, and outsole pattern. In this study, subjects are 21 adults (10 female, 11 male, age: $25.2{\pm}2.3yrs$, height: $165.6{\pm}7.2cm$), analysis variables were walking speed, GRF, when the UCOF is maximal, and Tangent of CoP-CoM angle, and correlation analysis with the utilized friction coefficient (UCOF). As a result, First, for the shod walking the time point which UCOF is maximum about heel strike was faster and the magnitude was larger than for barefoot walking. Second, the correlation between the tangent of CoP-CoM and UCOF of right foot was higher at the left heel striking point (UCOF2_h) which occurred in the post propulsion phase than at the right heel striking point (UCOF1_h). This suggests that the right foot UCOF is related to the braking phase of left foot( which is the propulsion phase of right foot) rather than the braking phase of right foot.

• The Journal of the Petrological Society of Korea
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• v.9 no.4
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• pp.254-270
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• 2000

To clarify the geological structure of North Sobaegsan Massif in the Sangunmyeon area, Bonghwagun, Korea, where the Yecheon Shear Zone passes and the NE-SW and E-W trending structural lineaments are developed, the rock-structures of its main constituent rocks(Precambrian Won-nam Formation and Mesozoic Hornblende Granite) were examined. In this area, the geological structure was formed at least by four phases of deformation after the formation of gneissosity or schistosity of the Wonnam Formation: one deformation before D2 ductile shearing related to the for-mation of the Yecheon Shear Zone and two deformations after that. The NE-SW and E-W trending structural lineaments were formed by a giant open or gentle type of F4 fold, and their trends before D4 deformation are interpreted to be parallel to the orientation(ENE-WSW trend) of folded surface in the F4 hinge zone. The structural features of Dl-D3 deformations and their relative occurrence times are as follows. Dl deformation is formative period of the boudin structures and ENE-WSW trending isoclinal folds with sub-horizontal hinge lines and steeply inclined axial surfaces. D2 deformation is that of the mylonite foliation, stretching lineation and Z-shaped asymmetric folds related to top-to-the ENE dextral strike-slip shearing on the distinct foliations of Wonnam Formation(after intrusion of Mesozoic Hornblende Granite). D3 deformation is that of the ENE trending S-shaped asymmetric folds with sub-horizontal hinge lines and axial surfaces related to normal-slip shearing on the distinct foliations. It is expected that the result will be contributed to as valuable data for interpreting the tectonic evolution of the North Sobaegsan Massif and the Northeast Ogcheon Belt whose tectonic lineaments are changed from NE-SW to E-W trends at the Sindong-Bonghwa line.

• The Journal of the Petrological Society of Korea
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• v.15 no.2 s.44
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• pp.49-59
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• 2006

This study clarifies the deformation history of Precambrian metamorphic rocks of Sobaegsan Massif (Wonnam Formation, Pyeonghae granite gneiss, Hada leucogranite gneiss) in Giseong-myeon area, Uljin-gun, Korea. It is based on the geometric and kinematic features and the developing sequence of multi-deformed rock structures. It also reviews the extension of Yecheon Shear Zone and the relative occurrence time of each deformation phase from previous researches. It suggests that the geological structure was formed at least through five phases of deformation after formation of their gneissosity or schistosity. (1) The first phase of deformation took placed under compression of ENE-WSW direction, forming NNW trending regional foliation and very tight isoclinal fold. The general trend of gneissosity or schistosity is inferred to be ENE before the first phase of deformation, being rearranged into NNW by the isoclinal folding. (2) The second phase of deformation formed ENE trending regional foliation and tight, isoclinal, rootless intrafolial folds under compression of NNW-SSE direction [occurrence time: after deposition (Permian age) of Dongsugok Formation, Pyeongan Croup, Janggunbong area]. (3) The third phase of deformation occurred by dextral ductile shearing on the regional foliation, forming stretching lineation of ENE trend and S-C mylonitic structure (after intrusion of Hesozoic homblende granite, Sangunmyeon area-before intrusion of Mesozoic Chunyang granite, Janggunbong area). (4) The fourth phase occurred under (E)NE-(W)SW compression, forming (N)NW trending open fold. (5) The fifth phase took place under N-S compression, forming NNE and NNW trending conjugate strike-slip faults, E-W trending thrust-slip faults, and drag folds related to these fault movements. The deformed structures of fourth and fifth phases result from tectonic movement associated with the developing of the Gyeongsang Basin in Cretaceous age, and it partially rearranged the general ENE trend of the regional foliation in the study area. It also suggests that the Yecheon Shear Zone of E-W trending extends into this area but the ductile shear deformation is weakly developed.

• The Journal of the Petrological Society of Korea
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• v.25 no.3
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• pp.195-209
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• 2016

The understanding of geometric complexity of strike-slip Fault system can be an important factor to control fault reactivation and surface rupture propagation under the regional stress regime. The Kumamoto earthquake was caused by dextral reactivation of the Futagawa-Hinagu Fault system under the E-W maximum horizontal principal stress. The earthquakes are a set of earthquakes, including a foreshock earthquake with a magnitude 6.2 at the northern tip of the Hinagu Fault on April 14, 2016 and a magnitude 7.0 mainshock which generated at the intersection of the two faults on April 16, 2016. The hypocenters of the main shock and aftershocks have moved toward NE direction along the Futagawa Fault and terminated at Mt. Aso area. The intersection of the two faults has a similar configuration of ${\lambda}$-fault. The geometries and kinematics, of these faults were comparable to the Yansan-Ulsan Fault system in SE Korea. But slip rate is little different. The results of age dating show that the Quaternary faults distributed along the northern segment of the Yangsan Fault and the Ulsan Fault are younger than those along the southern segment of the Yansan Fault. This result is well consistent with the previous study with Column stress model. Thus, the seismic activity along the middle and northern segment of the Yangsan Fault and the Ulsan Fault might be relatively active compared with that of the southern segment of the Yangsan Fault. Therefore, more detailed seismic hazard and paleoseismic studies should be carried out in this area.

• The Korean Journal of Petroleum Geology
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• v.5 no.1_2 s.6
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• pp.1-8
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• 1997

Seismic stratigraphic analysis of the high resolution profiles obtained from the southeastern shelf of Korea divided the deposits into 4 sequences; 1) sequence D, 2) sequence C, 3) sequence B and 4) sequence A (Holocene sediments). Sequence D was deposited in shallow-water environment at west of the Yangsan Fault as the basin subsided. On the other hand, the eastern part was formed at the slope front. Landward part of the slope-front fill sediments were eroded and redeposited nearby slope due to the syndepositional tilting of the basin. This tilting probably resulted from the continuous closing of the Ulleung Basin. Sequence C is made of stacked successions of the lowstand fluvial sediments, transgressive sediments and marine highstand sediments derived from the paleo-river in the western part of the Yangsan Fault. Sequence C in the eastern part of the Yanshan Fault was formed at the shelf break. Progradation of the lowstand sediments resulted in broadening of the shelf. Sequence C in the eastern part was also tilted but the tilting was weaker than in Sequence D. During the formation of sequence B the tilting stopped and the point source instead of the line source started in both sides of the Yangsan Fault. Sequence B was composed of the highstand systems tract partially preserved around the Yokji island, lowstand systems tract mainly preserved in the Korea Trough and transgressive systems tract. After the stop of the tilting, the force of compression due to the closing of the Ulleung Basin may be released by the strike-slip faults instead of tilting.

• The Journal of Engineering Geology
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• v.19 no.4
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• pp.509-515
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• 2009

Three earthquakes with local magnitude ($M_L$) greater than 3.0 occurred on April 24, June 2 and September 12 in 1999 nearby the Gyeongju area. Redetermined epicenters were located within the radius of 1 km. We carried out waveform inversion analysis to estimate focal mechanism of June 2 event, and P and S wave polarity and their amplitude ratio analysis to estimate focal mechanisms of April 24 and September 12 events. June 2 and September 12 events had similar fault plane solutions each other. The fault plane solution of April 24 event included those of other 2 events, but its distribution range was relatively broad. Focal mechanisms of those events had a strike slip faulting with a small normal component. P-axes of those events were ENE-WSW which were similar to previous studies on the P-axis of the Korean Peninsula. Considering distances between epicenters, similarities of seismic waves and sameness of polarities of seismic data recorded at common seismic stations, these events might occurred at the same fault. The seismic moment of June 2 event was estimated to be $3.9\;{\times}\;10^{14}\;N{\cdot}m$ and this value corresponded to the moment magnitude ($M_W$) 3.7. The moment magnitude estimated by spectral analysis was 3.8, which was similar to that estimated by waveform inversion analysis. The average stress drop was estimated to be 7.5 MPa. Moment magnitudes of April 24 and September 12 events were estimated to be 3.2 and 3.4 by comparing the spectrum of those events recorded at common single seismic station.

• Economic and Environmental Geology
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• v.2 no.4
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• pp.73-90
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• 1969

The area studied is a southwestern part of Okcheon geosynclinal zone which streches diagonally across the Korean peninsula in the mid-central parts of South Korea, and is bounded by Charyeong mountain chains in the north and by Sobaek mountain chains in the south. The general trend of the zone is of NE-SW direction known as Sinian direction. Okcheon system of pre-Cambrian age occupies southwestern portion of Okcheon geosynclinal zone, and Choseon and Pyeongan systems of Cambrian to Triassic age in northeastern portion of the zone. It was defined by the writer that the former was called "Okcheon Paleogeosynclinal zone" and the latter "Okcheon Neogeosynclinal zone," although T. Kobayashi named them "Metamorphosed Okcheon zone" and "Non-metamorphosed Okcheon zone" respectively and thought that sedimentary formations in both zones were same in origin and of Paleozonic age, and C.M. Son also described that Okchon system was of post-Choseon (Ordovician) and pre-Kyeongsang (Cretaceous) in age. According to the present study two zones are separated by great fault so that the geology in both zones is not only entirely different in origin and age, but also their geolosical structures are discontinuous. Stratigraphy and structure of Okcheon system are clearly established and defined by the writer and its age is definitely pre-Cambrian. It is clarified by present study that the meta-sediments in and at vicinity of Charyeong mountain chains are correlated to Weonnam series of pre-Cambrian age which occupies and continues from northeast to southwest in and at south of Sobaek mountain chains, and both metasediments constitute basement of Okcheon system. Pyeongan, Daedong and Kyeongsang systems were deposited in few narrow intermontain basins in Okcheon paleogeosynclinal zone after it was emerged at the end of Carboniferous period. Granites of Jurassic and Cretaceous ages and volcanics of Cretaceous age are cropped out in the zone. Jurassic granite is aligned generally with the trend of Okcheon geosynclinal zone, whereas Cretaceous granite lacks of trend in distribution. Many isoclinal folds and thrust faults caused by Taebo orogeny at the end of Jurassic period are also parallel with Sinian directieon and dip steeply to northwest. Charyeong, Noryeong, Sobaek, and Deogyu mountain chains are located in areas of anticlinorium, and Kyongsang system in narrow synclinal zones. Folds in Okcheon neogeosynclinal zone are generally of N 70-80W direction but deviate to Sinian direction at the western parts of the zone. This phenomena is interpreted by the fact that the folds were originated by Songrim disturbance at the end of Triassic period and later partly modified by Taebo orogeny. Thrust faults of Taebo orogeny coentinue from Okcheon paleogeosynclinal zone into neogeosynclinal zone, forming imbricated structure as previously described. Strike-slip faults perpendicular to Sinian direction and shear faults diagonally across it by 55 degrees also prevail in neogeosynclinal zone. It is concluded from viewpoints on geology and geological structure that l)Okchon geosyncline had changed its location and affected by numerous disturbances through geologic time, and 2)mountain chains in the area such as Charyeong, Noryeong, Sobaek, and Deogyu were originated as folded mountains. Differing from others, however, Sobaek range was probably formed at the time of Songrim disturbance and modified later by Taebo orogeny. It is cut by Danyang-Jeomchon fault at the vicinity of Joryeong near Munkyeong village and does not continue to southwest beyond the fault, whereas southwestern portion of erstwhile Sobaek range continues to Taebaek rangd northeastward from Deogyusan passing through Sangju, Yecheon, and Andong. From these evidences, the writer has newly defined the erstwhile Sobaek range in such a way that Sobaek range is restricted only to northeastern portion and Deogyu range is named for the southwestern portion of previous Bobaek range.

• Economic and Environmental Geology
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• v.32 no.4
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• pp.353-363
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• 1999

The Cretaceous and the Upper Jurassic strata of the Korean Peninsula, entirely of continental facies, form a sedimentary mega-unit subdivided into three unconformity-bounded units. The lower, Upper Jurassic-early Lower Cretaceous unit (Jasong Synthem) occurs profusely in North Korea and is characterized by volcanic rocks of intermediate to acidic, calc-alkaline to alkaline compositions; but strata of this unit is very rare in South Korea. The middle, Hauterivian-Lower Albian unit occurs commonly in the Korean Peninsula, but some alkalinesubalkaline basalt and andesite occur only in South Korea. A recently obtained U-Pb isochron age about 113.6 Ma (Chang et at, 1998) from the zircon grains of the Kusandong Tuff in the uppermost part of the Haman Formation has thrown much light on the age of this unit. The stratotype of this Hauterivian-L. Albian unit is the Sindong and Hayang Groups of the Kyongsang Basin, where the unit is about twice thick and has more conglomerates than in sedimentary basins in North Korea. The unit shows various sedimentary cycles in different basins showing that the cyclicity is controlled by local crustal motion. The upper, Upper Albian-Upper Cretaceous unit is abundant in South Korea with prolific volcanic rocks which are intermediate to acidic and notably calc-alkaline. In North Korea, however, this unit occurs in only one locality without volcanic rocks and is not voluminous. The distribution of these three unconformity-bounded units shows a stepwise younging toward the Pacific Ocean: the lower unit occurs mainly in N Korea, the middle unit occurs in both N and S Korea, and the upper unit occurs mainly in the southern part of S Korea. The Cretaceous sedimentary basins of S Korea were genetically controlled by paralleling sinistral strike-slip faults parallel to the Pacific margin.

• The Journal of Engineering Geology
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• v.26 no.4
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• pp.531-549
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• 2016

The purpose of this study is to analyze the relationship of hydrochemistry, geology, fault with occurrence of uranium and radon-222 from the groundwater in the Yeongdong area. In this study, 49 groundwater and 4 surface water samples collected in the study area were collected on two separate occasions. The surface radioactivities were measured at 40 points to know the relationship between the occurrence of uranium in groundwater and surface geology. The chemical composition of groundwater showed three types : $Ca-HCO_3$, $Na-HCO_3$ and $Ca-HCO_3(SO_4,\;NO_3)$. Two groundwater of 49 samples exceeded the maximum contaminant levels of uranium, $30{\mu}g/L$, proposed by the Ministry of Environment of Korea and 11 groundwater of 40 samples for Rn-222 concentrations exceeded the 148 Bq/L maximum contaminant level of US EPA. Most of unsuitable groundwater are located in the geological boundary related with the biotite gneiss and the surface radioactivities of rock samples showed no relationship with groundwater geochemical constituents. The strike-slip fault, Youngdong fault, is $N45^{\circ}E$ direction and the high concentrations of uranium in upper part of fault, consisted of granite and granitic gneiss are detected but in lower part, consisted of metamorphic sedimentary rock are not detected. It suggests that the natural radioactive concentrations are related with the geologic characteristics and the migration and diffusion of natural radioactive materials are affected by the fault.