• 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.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.241-245
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• 2003

This paper presents the LRB-based hybrid base isolation system employing additional semiactive control devices for seismic protection of cable-stayed bridges by examining the ASCE first generation benchmark problem for a cable-stayed bridge. In this study, ideal magnetorheological dampers (MRDs) are considered as additional semiactive control devices. Numerical simulation results show that the hybrid base isolation system is effective in reducing the structural responses of the benchmark cable-stayed bridge under the historical earthquakes considered. The simulation results also demonstrate that the hybrid base Isolation system employing semiactive MRDs is robust to the stiffness uncertainty of the structure. Therefore, the LRB-based hybrid base isolation system employing MRDs could be appropriate in real applications for full-scale civil infrastructures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.6
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• pp.821-831
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• 2019

The 9.12 earthquake (2016.9.12., M_L=5.8) and Pohang (2017.11.15., M_L=5.4) caused social and economic damage, resulting in a greater public interest in earthquakes than in the past. In the U.S., Japan and Chile, which have high frequency of earthquakes, infrastructure facilities are already managed based on probabilistic seismic hazard analysis (PSHA) and ground motion prediction equation (GMPE) to prepare for and respond to seismic disasters. In South Korea, the aforementioned PSHA and GMPE models have been developed independently through individual researchers. However, the limited disclosure of basic data, calculation methods, and final results created during the model development poses a problem of deploying new data without updating the earthquake that occurs every year. Therefore, this paper describes how to create flatfile, which is the basic data of GMPE, and how to process for seismic waves, and how to create intensity measures.

• The Journal of the Petrological Society of Korea
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• v.25 no.4
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• pp.325-334
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• 2016

Both 1900 years of historic literature and recent instrumental seismic records indicate the Korean Peninsula has repeatedly experienced small and large earthquakes. This study has used historical and instrumental records of Korea to investigate the characteristics of earthquakes in the peninsula. Results of GIS spatial analyses indicate Pyongyang, the capital of North Korea, is more vulnerable to the earthquake hazard than that of other regions in the Korean Peninsula. It is also noted that Pyongyang is exposed to high risks of other natural and social disasters because of the high population density and concentrated infra structures. Scenario shake map drawn up assuming a magnitude 6.7 earthquake, which was experienced in A.D. 502 in the area, indicates that 51.1% of the city are exposed to PGA 0.24 g or higher. Recent statistics by the Statistics Korea also indicates the North Korea is far more vulnerable to disasters than those in the South Korea. Results of the preliminary study provide essential information for comprehensive understanding of earthquake hazard estimation in Korea including the North Korea.

• Journal of Korean Association for Spatial Structures
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• v.17 no.4
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• pp.85-92
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• 2017

Base isolation system is generally used for low-rise buildings. For high-rise buildings subjected to earthquake loads, a mid-story isolation system was proposed and applied to practical engineering. In this study, seismic responses of high-rise buildings considering the installation story of the mid-story isolation system were evaluated. To do this, the 20-story and 30-story building were used as example structures. Historical earthquakes such as Kobe (1995), Northridge (1994) and Loma Prieta (1989) earthquakes were employed applied as earthquake excitations. The installation location of the mid-story isolation system was changed from the bottom of the $1^{st}$ floor to the bottom of the top floor. The seismic responses of the example building were investigated by changing the location of the isolation layer. Based on the analytical results, when the seismic isolation system is applied, story drift ratio and acceleration response are reduced compared to the case without the isolation system. When the isolation layer is located on the lower part of the building, it is most effective. However, in that case, the possibility that the structure is unstable increases. Therefore, an engineer should consider both structural efficiency and safety when a mid-story isolation system for a high-rise building is designed.

• Journal of the Korean Society of Safety
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• v.33 no.1
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• pp.81-87
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• 2018

The seismic response, the natural frequencies and the mode shapes of an offshore wind turbine with twisted tripod substructure subject to various pile-ground interactions are discussed in this paper. The acceleration responses of the tower head by four historical earthquakes are presented as the seismic response, while the other loads are assumed as ambient loads. For the pile-ground interactions, the fixed, linear and nonlinear models are employed to simulate the interactions and the p-y, t-z and Q-z curves are utilized for the linear and nonlinear models. The curves are designed for stiff, medium and soft clays, and thus, the seven types of the pile-ground interactions are used to compare the seismic response, the acceleration of the tower head. The mode shapes are similar to each other for all types of pile-ground interactions. The natural frequencies, however, are almost same for the three clay types of the linear model, while the natural frequency of the fixed support model is quite different from that of the linear interaction model. The wind turbine with the fixed support model has the biggest magnitude of acceleration. In addition, the nonlinear model is more sensitive to the stiffness of clay than the linear pile-ground interaction model.

• Journal of architectural history
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• v.32 no.3
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• pp.63-76
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• 2023

Homogot Lighthouse is located in Pohang of the easternmost of Korean Peninsula. Homogot has become first known as Cape Clonard in the West through the navigation log by La Perouse, a Frenchman who embarked on a global exploration in 1785. Homogot Lighthouse represents an outstanding accomplishment of modernization that numerous civilized countries scrambled to attain in the early 20^th century. Located where the geographical risk of earthquakes is high, the structure was nonetheless built to be 26.4m high with brick masonry. Structurally safe and aesthetically graceful, it demonstrates neoclassical ideas superbly in terms of style as well. Although the history of Asian lighthouses is shorter than that of European ones. Homogot Lighthouse, which demonstrates the history of a modern lighthouse along with those in Japan and China, is differentiated by the following characteristics. ① The 'living lighthouse heritage' is linked to one of the largest lighthouse museum in the world. ② Where you can see the earliest sunrise at the easternmost of the Eurasian Continent. ③ The completion of a modern-style lighthouse constructed at the easternmost of the Far East after being initiated in Europe. ④ Differentiated historical, architectural, and aesthetic value. ⑤ The heart of the national marine park.

• Geophysics and Geophysical Exploration
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• v.13 no.3
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• pp.187-197
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• 2010

The paleoseismological study in Korea has begun along the Yangsan fault zone (YFZ) and Ulsan fault zone (UFZ) since 1994. Some evidences related to late Quaternary movement are found at only some part of the YFZ, such as Pyonghae, Yuge, and Eonyang-Tongdosa areas. However, it is found along the most of the UFZ except the northen and southern ends of the fault. The dominant time span of faulting events along the YFZ and UFZ are quite different, and 500 ka to 200 ka and 300 ka to recent time, respectively. The dominant faulting senses of the YFZ and UFZ are right-lateral strike slip and reverse, respectively. These senses correspond well with the focal mechanism of recent occurring earthquakes along these two fault zones. If we evaluate the intensity of the activity of the YFZ from the average slip rate, which is 0.1~0.04 m/ka, it is comparable with the faults of higher C class in Japan. The slip rate of UFZ, which is 0.2~0.06 m/ka, is comparable with the faults of lower B to higher C class. Based on the relationship between maximum displacement and magnitude, the maximum earthquake magnitude is evaluated to be 6.8 and 7.0 in the YFZ and UFZ, respectively. An intensive studies are needed to clarify the problems such as segmentation of faults, return period, and geological evidences related to historical earthquakes.

• Journal of the Korean Society of Hazard Mitigation
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• v.2 no.2 s.5
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• pp.73-83
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• 2002

HAZUS developed by FEMA is applied to estimation on seismic hazard in Chung-Nam Province using basic data on general building, population, and geology of well-logging. Through the investigation on historical and instrumental earthquakes in Korean Peninsula seismic hazard is estimated in Chung-Nam Province in two ways for calculation of acceleration, deterministically and probabilistically. In deterministic method seismic hazard in Chung-Nam Province is estimated by generation of the maximum event that occurs in Hongsung and has magnitude of 6.0. According to the result, Hongsung Gun, Yesan Gun, and Boryung City are the most severe in building damage. The expected number of people who need hospitalization in Hongsung Gun and Yesan Gun due to the earthquake are 1.1 and 0.4, respectively. In probabilistic(return period of 5,000 year) method seismic hazard in Chung-Nam Province is estimated. According to the result, Gongju City is the most severe in building damage. The expected number of people who need hospitalization in Gongju City and Nonsan City due to the earthquake are 0.1 and 0.15, respectively.

• Journal of the Korean Geophysical Society
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• v.9 no.3
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• pp.219-230
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• 2006

Since the key issue that 'the Yangsan fault is seismically an active fault" was raised in 1983, thegeological and geomorphological studies of active fault have been made by many researchers. These studies are mainly focused on the Yangsan fault system(YFS) and Ulsan fault system(UFS) due to many historical earthquakes occurred in this area. There are two different types of active faultings under the ENE-WSW horizontal stress field in the southeastern part of the Korean Peninsula. The NNE-trending YFS is the most prominent right-lateral strike-slip fault and has a continuous trace about 200 km long. Some part of this system has been active during the late Quaternary with evidences clearly recognized on both the northern (Yugyeri and Tosung-ri areas) and southern parts (Eonyang to Tongdosa area) of the YFS. in the southern part, the estimated vertical slip rate is about 0.02 - 0.07 mm/yr, and the lateral slip rate may be several times larger than the vertical rate. The most recent event occurred prior to deposition of Holocene alluvium, in the northern part, the fault trend locally changes to almost N-S, dips to the east and has reverse movement. The average vertical slip rate is estimated to be less than 0.1 mm/yr. The most recent event probably occurred after 1314 years BP (AD 536). The NNW-SSE (or N-S) trending UFS is a predominantly reverse fault that built up U-ie eastern mountain and has been active during U-ie late Quaternary. The fault trace is not straight but irregularly undulates along the foot of the mountain on the east. From the disturbed terraces along U-ie fault, the average vertical slip rate on U-iis system is estimated to be about 0.08.13mm/yr. The latest event is not well studied, but seems to have occurred after the last glacial maximum in the Malbang fault and 14,000 years BP in the Kalgok fault of the UFS. However, important issues such as fault segmentation, recurrence interval, age of Quaternary deposits need further studies.