• 한국지진공학회논문집
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• 제19권5호
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• pp.247-256
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• 2015

This paper briefly introduces the design seismic loads in Korea (KBC 2009). Then, over 10,000 recorded earthquake ground accelerograms, with their magnitude ranging from 4.0 to 8.0 and their epicentral distance ranging from 0 to 200 km, were used to examine the appropriateness of seismic load defined in Korea known as a low-to-moderate seismicity region. The following conclusions are drawn based on the results: (1) The effective peak ground accelerations (EPA) of recorded earthquake accelerograms under $M{\leq}6.0$ and $R{\geq}15km$ appear to be less than that of MCE in Korea for all site conditions defined in KBC 2009. (2) The design spectrum (two-thirds of the intensity of MCE) in KBC 2009 is comparable to those of earthquake records in the magnitude 6 - 7 and the epicentral distance less than 50 km. Therefore, (3) the intensity of Korean design earthquake is considered to be overly high since the Korea peninsula is generally conceived to be a low-seismicity region.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1998년도 가을 학술발표회 논문집
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• pp.497-504
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• 1998

In the nonlinear dynamic structural analysis, the given ground excitation as an input should be well defined. Because of the lack of recorded accelerograms in Korea, it is required to generate an artificial earthquake by a stochastic model of ground excitation with various dynamic properties rather than recorded accelerograms. It is well own that earthquake motions are generally non-stationary with time-varying intensity and frequency content. Many researchers have proposed non-stationary random process models. Yeh and Wen (1990) proposed a non-stationary stochastic process model which can be modeled as components with an intensity function, a frequency modulation function and a power spectral density function to describe such non-stationary characteristics. This model is based on the simulation for the strong-motion earthquakes with magnitude greater than approximately 5.0~6.0, because it will be not only expected to cause structural damage but also involved the characteristics of earthquake motions. Also, the recorded earthquake motion within this range are still very scarce in Korea. Thus, it is necessary to verify the model by the application of it to the mid-magnitude (approximately 4.0~6.0) earthquakes actually recorded in domestic or foreign area. The purpose of the paper is to generate an artificial earthquake using the model of Yeh and Wen in the area with low seismicity.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2003년도 춘계 학술발표회논문집
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• pp.3-11
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• 2003

We analysed phases recorded by the M$_{L}$ 3.6 Cheolwon, Korea, earthquake occurred on the 10th of December, 2002 and computed source parameters such as hypocenter, origin time, earthquake magnitude and focal solutions. We used PmP and SmS phases to increase the accuracy in determinations of the hypocenter and origin time in addition to the phases such as Pg, Pn, Sg and Sn which are generally used in routine processes. The epicenter, depth, and origin time of the Cheolwon earthquake determined based on data of 11 stations within 200 km from the epicenter are 38.8108$^{\circ}$N, N, 127.2214'E, 11.955 km, and on 7:42:51.436. The earthquake magnitude obtained from all the stations is 3.6 M$_{L}$. The fault plane solution calculated based on data from 19 stations indicates slip process of a normal fault including strike-slip motion. The direction of compressional stress field has a large vertical component and a ESE-WNW direction of horizontal component, which is different from the mainly horizontal direction of main compressional stress field in the Korean Peninsula (ENE-WSW) obtained by previous studies.ies.s.

• Structural Engineering and Mechanics
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• 제49권3호
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• pp.355-372
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• 2014

Considering the history of severe earthquakes and the presence of active faults in the greater Tehran region, the possibility of a destructive earthquake occurring is high and seismic hazard analysis is crucial. Gumbel distributions are commonly-used statistical distributions in earthquake engineering and seismology. Their main advantage is their basis on the largest earthquake magnitudes selected from an equal-time predefined set. In this study, the first asymptotic distribution of extremes is used to estimate seismicity parameters and peak ground acceleration (PGA). By assuming a Poisson distribution for the earthquakes, after estimation of seismicity parameters, the mean return period and the probable maximum magnitude within a given time interval are obtained. A maximum probable magnitude of 7.0 has a mean return period of 100 years in this region. For a return period of 475 years, the PGA in the greater Tehran region is estimated to be 0.39g to 0.42g, depending on local site conditions. This value is greater than that of the Iranian Code for Seismic Design of Buildings, indicating that a revision of the code is necessary.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2000
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• pp.91-97
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• 2000

Once a response spectrum is estimated for the site, if there is a need of generating realistic earthquakes time histories considering seismic sources and path effects, one alternative is to use statistical phase characteristics based on real earthquake records other than assuming arbitrary duration and envelope curves. In this study, statistics of group delay times derived from Japanese strong earthquake data were used for phase generation to fully capture the stochastic property of earthquakes. The result shows that simulated earthquake time histories can be generated according to earthquake magnitude and distances with target response spectrum.

• 지구물리
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• 제7권3호
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• pp.185-192
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• 2004

2001년 1월부터 2004년 2월까지 한반도 남부 지역에서 발생한 지진의 모멘트규모를 계산하여 기상청과 한국지질자원연구원의 지역규모와의 관계를 분석하였다 분석 결과 기상청의 지역규모는 한국지질자원연구원의 지역규모에 비해 모멘트규모와의 상관성이 낮은 것으로 나타났다 또한 발표된 지역규모와 계산된 모멘트규모의 회귀 분석을 통해 모멘트규모 환산식을 유도하였다 유도된 모멘트규모 환산식은 지진목록의 규모 단일화에 이용될 수 있고 규모가 단일화된 지진목록은 지진활동 특성 분석 지진재해도나 감쇄식 등에 필요한 인자로서 활용될 수 있다

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.503-510
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• 2006

Seismic control performance of MR dampers, which have severe nonlinearity, differs with respect to the dynamic characteristics of an earthquake such as magnitude, frequency and duration. In this study, the effects of excitation characteristics on the equivalent linear system of a building structure with an MR damper are investigated through numerical analysis for artificial ground motions generated from different response spectrums. The equivalent damping ratio of the structure with an MR damper is calculated using Newmark and Hall's equations for ground motion amplification factors. It is found that the equivalent damping ratio of the structure with the MR damper is dependent on the ratio of the maximum friction force of the MR damper over excitation magnitude. Frequency contents of the earthquake ground motion affects the equivalent damping ratio of long-period structures considerably. Also, additional damping effect caused by interaction between the viscousity and friction of the MR damper is observed.

• 한국지반공학회논문집
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• 제18권4호
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• pp.329-337
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• 2002

최근까지 지반의 액상화 저항강도를 산정하기 위한 실내시험의 대부분은 실지진하중을 재하하기보다는 Seed와 Idriss(1975)가 제안한 등가전단응력 개념에 기초하여 지진이 발생시키는 최대전단응력의 65%를 최대진폭으로 한 정현하중을 반복재하시켜왔다. 이러한 정현하중이 정확하게 실제 지반에 작용하는 불규칙한 지진력을 모사하고 있다고 볼 수 없으나, 시험상의 편의성으로 인해 현재까지도 이용이 빈번한 실정이다. 본 연구에서는 실제 지진하중 하에서 포화 사질토의 거동변화를 규명하고자 정현하중이 아닌 불규칙한 지진하중을 이용한 실험적 연구를 수행하였다. 다양한 지진규모의 실지진 시간이력을 진동하중으로 작용시킨 진동삼축시험을 통해 지진규모 및 지속시간의 변화에 따른 포화사질토의 동적 특성을 실험적으로 규명하고 기존의 등가전단응력 개념에 기초한 액상화 저항강도와 비교분석하였다. 또한, 중약진 지진대로 구분되는 국내 실정을 고려하여 다양한 지진규모에 적용가능한 수정계수를 제시하고 이를 기존의 연구결과와 비교분석하였다.

• Earthquakes and Structures
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• 제8권6호
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• pp.1463-1480
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• 2015

This research aims to develop an empirical model for simulation of time-varying frequency in earthquake ground motion so as to be used easily in engineering applications. Briefly, 10545 recordings of the Next Generation Attenuation (NGA) global database of accelerograms from shallow crustal earthquakes are selected and binned by magnitude, distance and site condition. Then the wavelet spectrum of each acceleration record is calculated by using one-dimensional continuous wavelet transform, and the frequencies corresponding to the maximum values of the wavelet spectrum at a series of sampling time, named predominant frequencies, are extracted to analyze the variation of frequency content of seismic ground motions in time. And the time-variation of the predominant frequencies of 178 magnitude-distance-site bins for different directions are obtained by calculating the mean square root of predominant frequencies within a bin. The exponential trigonometric function is then use to fit the data, which describes the predominant frequency of ground-motion as a function of time with model parameters given in tables for different magnitude, distance, site conditions and direction. Finally, a practical frequency-dependent amplitude envelope function is developed based on the time-varying frequency derived in this paper, which has clear statistical parameters and can emphasize the effect of low-frequency components on later seismic action. The results illustrate that the time-varying predominant frequency can preferably reflect the non-stationarity of the frequency content in earthquake ground motions and that empirical models given in this paper facilitates the simulation of ground motions.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.31-38
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• 1998

In this study, statistical analyses implemented in the EPRI EQHAZARD programs were employed to estimate the sismicity parameters in the Korean peninsula based upon an combined Korean earthquake catalog. The combined earthquake catalog was prepared by performing earthquake clustering analysis on the collected earthquake catalogs provided by experts of the seismic panel during the PSA for Yonggwang Units 1 & 2. The duplicate earthquake events and secondary events in earthquake clusters have been successfully screened. The resultant earthquake catalog was analyzed to quantitatively assess the incompleteness of the earthquake catalog for specified earthquake magnitudes and time periods. The result shows that the earthquake catalog of the Korean peninsula is complete for the times periods of 1392 ~ 1750 and 1905 ~ 1989 (AD) and earthquake magnitude above 4.5. The PSHA methodology of EQHAZARD features the estimation of inhomogeneous a-and b-values within a seismic source. This study shows various results of a-and b-value is well constrained lying between o.6 and 1.0. Also the confidence of estimated a-and b-value for a specifed location was assessed by quantifing the uncertainty of these parameters using bootstrap simulation.