• Economic and Environmental Geology
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• v.26 no.2
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• pp.227-237
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• 1993

Lineaments in the Kyungsang basin most intensely develop in the East coast domain including the Yangsan fault, which dominantly run in NNE direction. The geometry of small fault population near or along the Yangsan fault represents the dominant strikes of N35E, high angle dips and shallowly plunging rakes with dextral movement sense. Stereographic solution on the Yangsan fault geometry gives the dip of 88SE, the slip direction of 17,024 and the slip rake of 18, which were determined from the strike (N23E) of the fault measured on map, and the average attitude (N35E, 84SE) and fault striation (16, 037) of small fault population considered as Riedel shears. It is judged from the geometry of small fault population to the main Yangsan fault and dragging features of bedding attitude near the fault that the Yangsan fault was produced from dextrally strike-slip movement. The movement of the Yangsan and the adjacent parallel faults is thought to be taken place much later than the other fault sets in the Kyungsang basin. It might occur during the geologic age from Eocence to early Miocene according to the consideration of K-Ar ages of the igneous rocks near the fault. The estimated paleostress state indicates ENE shortening and NNW extension. The displacement of the Yangsan fault in the study area is not constant along the fault but decreases from the south to the north. Taking the northern end of the study area as a separating point the whole extension of the Yangsan fault may be divided into southern and northern segments.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.10a
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• pp.228-234
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• 1998

To interpret the relationship between movement of the Yangsan fault and tectonics around the Korean peninsula, the six sequential paleostresses were reconstructed from 1, 033 striated small faults which were measured at 37 outcrops along the strike of the Yangsan fault. And, the relationship between these paleostresses of the Yangsan fault and the tectonic events around the Korean peninsula were compared. As compared with the tectonic history around the Korean peninsula, the movement of the Yangsan fault is interpreted as follows; The initial feature of the Yangsan fault was formed with the development of extension fractures by the NW-SE extension. The fault experienced a right-lateral strike-slip movement continuously. The movements had been continued until the Late Miocene age, which was the most active period in faulting. The left-lateral strike-slip movement was followed by subsequent tectonic events. In the last stage, the fault acted with a slight extension or right-lateral movement.

• Journal of The Geomorphological Association of Korea
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• v.25 no.1
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• pp.19-30
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• 2018

This study tries to infer fault lines and produce a map for the lines based on a classification of fault-related landforms and fluvial landformsin the Gyeongju area of the Yangsan Fault Valley. Fault activities in the study area are thought to be older than the time of river formation or stronger than the erosion by river, while the northern and southern parts of the study area seem to have experienced fault activities after valley formation. It is also possible that weaker fault activities than the erosion by river seem to have been prevailed in the parts. In the study area, the Gyeongju alluvial fan is located within a wide erosional valley at the joint area of the Yangsan and Ulsan Faults. From the distribution of the landforms, it is inferred that several fault lines parallel to the Yangsan Fault are distributed at both sides of the fault valley. In particular, the area from Bae-dong to Nogok-ri, Naenam-myeon shows the most obvious linearity of the landforms within the study area. Several fault lines with a direction of NNE-SSW are also found around the epicenter of the 2016 Gyeongju Earthquake.

• The Journal of Engineering Geology
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• v.19 no.3
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• pp.277-285
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• 2009

In order to assess the fault behavior by the geometric analysis of fault slip, the study area between Yangsan city and Shinkwang-myon, Pohang city along the strike of the Yangsan fault is divided into 5 domains($A{\sim}E$ domains) based on the strike change of main fault, the type of fault termination, the cyclic variation of fault zone width, deformation pattern of fault rocks and angular deviation of secondary shears. And, we would apply the relationship between the mode of fault sliding and the resultant deformation texture obtained from previous several experimental studies of simulated fault gouge to the study of the Yangsan fault. To understand sliding behavior of the fault we measured the data of fault attitude and fault slip, and analyzed relationships between the main fault and secondary Riedel shear along the Yangsan fault. The sliding behavioral patterns in each section were analyzed as followings; the straight sections of A, D and E domains were analyzed as the creeping section of stably sliding. In contrast, the curved section of B domain was analyzed as the locked section of stick-slip movement.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.30-37
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• 2003

Lineaments along the Yangsan and Ulsan fault systems were extracted through aerial photograph interpretation in the southeastern part of Korean Peninsula. Lineaments can be classified into five ranks on the basis of certainty and divided by curvatures. Mean strikes of all lineament by aerial photograph interpretation is dominant in NS ~N05$^{\circ}$E direction along the Ulsan fault system and Nl5-20$^{\circ}$E direction along the Yangsan fault system respectively. The curvature of lineament around Yangsan Fault is different from around the Ulsan Fault system, the former shows that straight lineament is dominant but the latter curved lineaments are dominant. It indicates that the Quaternary faults around Ulsan Fault would be appeared as reverse fault.

• Economic and Environmental Geology
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• v.49 no.2
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• pp.97-104
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• 2016

Here we firstly present that a timing of reactivated event of Yangsan fault, the major fault in the southeastern Korean Peninsula, by using combined approaches of the optimized illite-polytype quantification, the K-Ar age-dating, and the recently developed illite-age-analysis (IAA) approach for the fault clays from Sangcheon-ri area of Yangsan main fault line. Two chronological record of brittle fault-activation event at about 41.5~43.5 and 50.7 Ma were determined from 3 fault gouges suggesting a crucial reactivation time-scheme. Furthermore, the regional processes that drive tectonics to form and reactivate the Yangsan fault may be explained from the chronological analysis for additional sites along the Yangsan fault.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1997.10a
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• pp.49-56
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• 1997

Most large strike-slip faults do not rupture their entire length during single faulting but generally break in segments which are different in location and time of faulting. Studies related to the development of the Yangsan fault have been reported based on partial results from characteristics of geolgocial distribution, geophysical prospecting and paleostress analyses. This paper shows, based on preliminary results, that the Yangsan fault could be divided into four structural areas along entire length. These areas are different in geological distribution, bedding attitude measured from sedimentary rocks, strike of main fault, geometry of small faults, termination types of fault tips, cyclic variation of fault zone width, and arrangement of paleostress. Therefore, the Yangsan fault could be divided into at least four segments.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.28 no.2
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• pp.289-295
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• 2010

Yangsan fault system is a large fault more than 170km and one of the important structures Geologically that has been create recently in the Korean Peninsula. Debates have been made incessantly and widely throughout the Yangsan fault system because it's a lot of earthquake record. In this study, GPS data that was received from Yangsan GPS station in were processed by the Precise Point Positioning and the movement velocity was calculated by the statistical process about the results, where is the fault zone. The results showed that Yangsan is moving by azimuth angle of $126^{\circ}$ and the velocity of 49mm/year. It is respected that this results will be utilized in basic data about geophysics.

• Journal of The Geomorphological Association of Korea
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• v.28 no.1
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• pp.67-81
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• 2021

Geomorphological development and distribution at the macro scale provide a clue to the geotectonic characteristics that have affected the geomorphological system. This is because the developmental characteristics and distribution of the landform at the macro scale remain spatial characteristics due to tectonic processes, such as fault activity. From the perspective of tectonic geomorphology, this study identified the developmental characteristics and distribution of the Quaternary landforms in central-southern Yangsan fault and discussed its relevance to fault activity. In this paper, we presented examples and results of morphotectonic analysis of the Yangsan fault, and will present the results of age dating, stratigraphic relationship of the Quaternary landforms, and calculation of cumulative slip rate in the next paper.

• Journal of the Korean Geophysical Society
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• v.2 no.3
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• pp.155-168
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• 1999

The paleoseismological importance of the Yangsan fault zone was examined by historical earthquake data, aerial photograph, and trench survey of the area. Occurrences of great earthquakes during the historical time indicate that the Yangsan and/or Ulsan fault have been active during the late Quaternary and generated historical events. Geomorphological evidences of the recent fault activity are clearly shown both in the northern segment (Yugye-ri, Tosung-ri and Naengsu-ri areas) and in the southern segment (Eonyang to Tongdosa areas) of the Yangsan fault. The main Yangsan fault is characterized by fault gouges and NNE-SSW lineaments. The reverse faulting in the Yugye-ri area generated about three-mater displacement of the lower terrace deposits. On the other hand, a major strike-slip movement with a minor component of 5-12 m vertical displacement was identified by the offset of the higher terrace surface in the Eonyang area.