• Earthquakes and Structures
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• 제20권4호
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• pp.445-455
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• 2021

Lake Van Basin, located in Eastern Turkey, is worth examining in terms of seismicity due to large-scale losses of property and life during the historical and instrumental period. The most important and largest province in this basin is Van. Recent indicators of the high seismicity risk in the province are damage occurring after devastating earthquakes in 2011 (Mw=7.2 and Mw=5.6) and lastly in 2020 Khoy (Mw=5.9). The seismic hazard analysis for Van and its districts in Eastern Turkey was performed in probabilistic manner. Analyses were made for thirteen different districts in Van. In this study, information is given about the tectonic setting and seismicity of Van. The probabilistic seismic hazard curves were obtained for a probability of exceedance of 2%, 10% and 50% in 50-year periods. The PGA values in the Van province vary from 0.24 g - 0.43 g for earthquakes with repetition period of 475 years. Risk priorities were determined for all districts. The highest risk was calculated for Çaldıran and the lowest risk was found for Gürpınar. Risk priorities for buildings in all districts were also determined via rapid seismic assessment for reinforced-concrete and masonry buildings in this study.

• 지구물리와물리탐사
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• 제19권2호
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• pp.97-104
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• 2016

우리나라 남동부에 위치한 경주와 그 주변지역에서는 과거부터 최근까지 크고 작은 지진이 반복적으로 발생하고 있다. 계기지진자료를 검토하여 경주 주변 약 $20km{\times}30km$ 지역 내에서 지진이 많이 발생하고 있음을 확인하였다. 본 연구에서는 이 지역에서 2010년 1월부터 2014년 12월 사이에 발생했지만, 그 규모가 너무 작아 미처 보고되지 않은 300개 이상의 미소지진을 식별하고 그 발생위치를 결정하였다. 연구지역 지하의 속도구조와 진원요소 결정에 사용하는 속도모델의 차이로 인한 오차를 줄이기 위하여 JHD 방법을 사용하였다. 연구지역에서는 활성으로 의심되는 제4기 단층들이 여러 장소에서 보고되고 있으므로, 이 단층들과 미소지진발생과의 관련 가능성을 조사하였다. 본 연구에서 새로이 발생사실이 보고되는 미소 지진들은 연일구조선의 남측분절, 석읍단층 그리고 와읍분지 경계단층과 관련이 있는 것으로 나타난다.

• 한국지진공학회논문집
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• 제25권2호
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• pp.59-69
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• 2021

Historical records of earthquakes are generally used as a basis to extrapolate the instrumental earthquake catalog in time and space during the probabilistic seismic hazard analysis (PSHA). However, the historical catalogs' input parameters determined through historical descriptions rather than any quantitative measurements are accompanied by considerable uncertainty in PSHA. Therefore, quantitative assessment to verify the historical earthquake parameters is essential for refining the reliability of PSHA. This study presents an approach and its application to constrain reliable ranges of the magnitude and corresponding epicenter of historical earthquakes. First, ranges rather than specific values of ground motion intensities are estimated at multiple locations with distances between each other for selected historical earthquakes by reviewing observed co-seismic natural phenomena, structural damage levels, or felt areas described in their historical records. Based on specific objective criteria, this study selects only one earthquake (July 24, 1643), which is potentially one of the largest historical earthquakes. Then, ground motion simulations are performed for sufficiently broadly distributed epicenters, with a regular grid to prevent one from relying on strong assumptions. Calculated peak ground accelerations and velocities in areas with the historical descriptions on corresponding earthquakes are converted to intensities with an empirical ground motion-intensity conversion equation to compare them with historical descriptions. For the ground motion simulation, ground motion prediction equations and a frequency-wavenumber method are used to consider the effects of possible source mechanisms and stress drop. From these quantitative calculations, reliable ranges of epicenters and magnitudes and the trade-off between them are inferred for the earthquake that can conservatively match the upper and lower boundaries of intensity values from historical descriptions.

• 암석학회지
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• 제25권4호
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• pp.325-334
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• 2016

한반도에서는 크고 작은 지진이 꾸준히 발생하고 있음을 역사문헌과 계기지진 관측 자료를 통해 알 수 있다. 본 연구에서는 역사지진과 계기지진 자료를 이용해 지리정보시스템(GIS)의 공간분석 결과, 북한의 평양지역이 지진으로부터 가장 위험한 지역으로 결정되었다. 평양은 북한의 수도로서 인구와 구조물의 밀집도가 높아 지진뿐만 아니라 재해로 인해 큰 위험에 처할 수 있다. 502년 평양에서 발생한 규모 6.7의 지진을 토대로 지진동 지도를 작성한 결과, 0.24 g보다 높은 지진동을 느낄 수 있는 지역이 평양지역의 약 51.1%를 차지한다. 또한 통계청 자료에 의하면 북한은 우리나라보다 재해로부터 열악한 환경에 처해 있음을 확인할 수 있었다. 이번 연구결과는 향후 북한을 포함한 우리나라의 포괄적인 지진재해예측 연구에 유용한 정보로 사용될 수 있다.

• 한국지진공학회논문집
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• 제14권2호
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• pp.49-56
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• 2010

계기에 의한 진도산정은 보통 PGA와 진도와의 경험적인 관계식으로부터 계산되어 왔다. 그러나 일본 기상청은 지진에 의한 피해의 정도는 관측된 PGA보다는 진도와 상관이 더 크다는 점에 착안하여, 지진 계측기에 의해 실시간으로 진도를 산정(JMA 계측 진도)함으로서 지진재해를 좀 더 정확히 평가하는 방안을 채택하고 있다. 이 연구의 목적은 국내에서의 JMA 계측진도의 실제적인 활용방안을 제시하는 것이다. 한반도는 강진의 발생빈도가 낮기 때문에 사용할 수 있는 강진자료가 충분치 않다. 따라서 한반도의 지진원 특성과 감쇠특성에 맞는 강진동을 추계학적인 방법으로 합성하였다. 이러한 방법으로 합성된 강진자료에 대하여 JMA 계측진도를 포함한 6개의 공학적 지진동 상수들을 계산하였다. 다음으로 계산된 상수들 사이의 경험적인 관계식을 결정하였으며, 이 상수들을 몇 개의 그룹으로 분류하기 위한 군집분석을 수행하여 지진동 상수들을 분류하였다. 그 결과, JMA 가속도 ($a_0$)는 스펙트럼 진도와 유사한 그룹으로 분류되었으며, CAV(Cumulative Absolute Velocity)와는 비교적 관계가 먼 그룹으로 나타났다. JMA 계측진도는 지진재해 평가에 있어서 다른 하나의 평가척도로서 사용이 기능할 것으로 생각된다. 한편 지진재해의 예측에 활용이 가능한 PGA와 $a_0$에 대한 감쇠식이 모멘트 규모와 진원거리의 함수로 유도되었다.

• Earthquakes and Structures
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• 제15권1호
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• pp.29-44
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• 2018

A ground-motion prediction equation (GMPE) for the Korean Peninsula, especially for South Korea, is developed based on synthetic ground motions generated using a ground motion model derived from instrumental records from 11 recent earthquakes of $M_L$>4.5 in Korea, including the Gyeongju earthquake of Sept. 12. 2016 ($M_L$5.8). PSAs of one standard deviation from the developed GMPE with $M_W$ 6.5 at hypocentral distances of 15 km and 25 km are compared to the design spectrum (soil condition, $S_B$) of the Korean Building Code 2016 (KBC), indicating that: (1) PSAs at short periods around 0.2 sec can be 1.5 times larger than the corresponding KBC PSA, and (2) SD's at periods longer than 2 sec do not exceed 8 cm. Although this comparison of the design spectrum with those of the GMPE developed herein intends to identify the characteristics of the scenario earthquake in a lower-seismicity region such as South Korea, it does not mean that the current design spectrum should be modified accordingly. To develop a design spectrum compatible with the Korean Peninsula, more systematic research using probabilistic seismic hazard analysis is necessary in the future.

• Nuclear Engineering and Technology
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• 제42권1호
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• pp.55-64
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• 2010

The KIER's Korean historical earthquake catalog was revised for MMI${\geq}$VI events recorded from the years 27 A.D. to 1904. the magnitude of each event was directly determined from the criteria suggested by Seo. The criteria incorporated the damage phenomena of the Japanese historical earthquake catalog, recent seismological studies, and the results of tests performed on ancient structures in Korea. Thus, the uncertainty of the magnitudes of the Korean historical earthquakes can be reduced. Also, the Gutenberg-Richter parameter values were estimated based on the revised catalog of this study. It was determined that the magnitudes of a maximum inland and minimum offshore event were approximately 6.3 and 6.5, respectively. The Gutenberg-Richter parameter pairs of the historical earthquake catalog were estimated to be a=5.32${\pm}$0.21, b=0.95${\pm}$0.19, which were somewhat lower than those obtained from recent complete instrumental earthquakes. No apparent change in the Gutenberg-Richter parameter is observed for the $16^{th}-17^{th}$ centuries of the seismically active period.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.28-35
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• 2000

The quality factor and the seismic source parameters such as the $\chi$ corner frequency and the stress drop were estimated from the small-to-medium instrumental earthquake data in south Korea. The Q facter with 95% confidence level ranges from 1519 to 2158. The regression equation of $\chi$in terms of epicentral distance R, is obtained as $\chi$=0.006717+0.00015R. And the stress drop is estimated as 50 bar which is similar to the previous results carried out by independent researchers. Artificial ground motions were simulated using the estimated earthquake parameter values and compared with real earthquake, The simulated response spectrum is very similar to real one.

• 한국지진공학회논문집
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• 제22권3호
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• pp.211-217
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• 2018

The Pohang earthquake with a magnitude of 5.4 occurred on November 15, 2018. The epicenter of this earthquake located in south-east region of the Korean peninsula. Since instrumental recording for earthquake ground motions started in Korea, this earthquake caused the largest economic and life losses among past earthquakes. Korea is located in low-to moderate seismic region, so that strong motion records are very limited. Therefore, ground motions recorded during the Pohang earthquake could have valuable geological and seismological information, which are important inputs for seismic design. In this study, ground motions associated by the 2018 Pohang earthquake are generated using the point source model considering domestic geological parameters (magnitude, hypocentral distance, distance-frequency dependent decay parameter, stress drop) and site amplification calculated from ground motion data at each stations. A contour map for peak ground acceleration is constructed for ground motions generated by the Pohang earthquake using the proposed model.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 춘계학술대회 논문집
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• pp.58-65
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• 2001

It is essential to know exactly what the response of the seismograph is inclusive of characteristic of the seismic sensors before using it for detailed seismic study. This is because the recorded earthquake data can be more or less affected by the overall system and need to be corrected properly to the analysis`s best to obtain the right results. In this respect, two basic earthquake data processing techniques are introduced and applied, for validation purpose, to real data from KEPRI seismic monitoring system which were established for determining the site-specific characteristics of the earthquakes around the Nuclear Power Plants. One is conventional instrumental correction technique for velocity data and the other is for removing acausal ringing originate from using linear phase FIR filter. These techniques are all implemented in the time domain using digital filtering process and shows the desired results when applied to real earthquake data.