• Computational Structural Engineering
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• v.2 no.4
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• pp.111-116
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• 1989

Methods for the estimation of the coefficient matrices in the equation of motion for a linear multi-degree-of-freedom structure are studied. For this purpose, the equation of motion is transformed into an auto-regressive and moving average with auxiliary input(ARMAX) model. The ARMAX parameters are evaluated using several methods of parameter estimation : such as the least squares, the instrumental variable, the maximum likelihood and the limited information maximum likelihood methods. Then the parameters of the equation of motion are recovered therefrom. Numerical example is given for a 3-story building model subjected to an earthquake exitation.

• The Journal of Engineering Geology
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• v.10 no.2
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• pp.79-97
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• 2000

Trend of earthquake occurrence of Korea represents that the term from 1978 to 1982 may be called as "active period", the term from 1983 to 1991 is rather tranquil, and from 1992, the occurrence number is increasing greatly. Instrumental earthquake observation of Korea started in 1905 by Japan. It continued until 1943 and ceased then through social disorders such as the independence from Japan Empire and the civil war. After that the observation restarted in 1963 by the establishment the World Wide Standard Seismograph Network. And the fundamental earthquake observation period started in 1978 with the Hongsung earthquake event. KMA(Korea Meteorological Administration) has constructed and operated the 24-hour earthquake and tsunami monitoring system and it propels new construction project of the national seismographic network system. In the result of this project, KMA operates 27 seismic networks, 42 accelerator networks, seismic analyzing system, and sea level monitoring system now. It has the plan to enlarge these systems that 31 seismic networks and 75 accelerator networks until 2001.

• Journal of the Earthquake Engineering Society of Korea
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• v.22 no.6
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• pp.323-332
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• 2018

Recent two moderate earthquakes (2016 $M_w=5.4$ Gyeongju and 2017 $M_w=5.5$ Pohang) in Korea provided the unique chance of developing a set of relations to estimate instrumental seismic intensity in Korea by augmenting the time-history data from MMI seismic intensity regions above V to the insufficient data previously accumulated from the MMI regions limited up to IV. The MMI intensity regions of V and VI was identified by delineating the epicentral distance from the reference intensity statistics in distance derived by using the integrated MMI data obtained by combining the intensity survey results of KMA (Korea Meteorological Administration) and 'DYFI (Did You Feel It)' MMIs of USGS. The time-histories of the seismic stations from the MMI intensity regions above V were then preprocessed by applying the previously developed site-correction filters to be converted to a site-equivalent condition in a manner consistent with the previous study. The average values of the ground-motion parameters for the three ground motion parameters of PGA, PGV and BSPGA (Bracketed Summation of PGA per second for 30 seconds) were calculated for the MMI=V and VI and used to generate the dataset of the average values of the ground-motion parameters for the individual MMIs from I to VI. Based on this dataset, the linear regression analysis resulted in the following relations with proposed valid ranges of MMI. $MMI=2.36{\times}log_{10}(PGA(gal))+1.44$ ($I{\leq}MMI$$MMI=2.44{\times}log_{10}(PGV(kine))+4.86$ ($I{\leq}MMI$$MMI=2.59{\times}log_{10}(BSPGA(gal{\cdot}sec))-1.02$ ($I{\leq}MMI$

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.6
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• pp.27-37
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• 2009

A method of instrumentally estimating seismic intensity (MMI) based on the Fourier Acceleration Spectrum of earthquake ground-motion, the so-called 'FAS MMI method' of Sokolov and Wald (2002), was evaluated for its applicability to Korea based on the empirical models of mean (m) and standard deviation (${\sigma}$) for Korea according to individual seismic intensity for MMI ${\leq}$ IV (Yun et al., 2009). This evaluation showed that the error in estimating the seismic intensity using the FAS MMI method is ${\sigma}$ = 0.74 MMI, and was further reduced to ${\sigma}$ = 0.61 MMI if the dependency of the error on earthquake magnitude and distance is additionally corrected. It is also shown that FAS MMI based on the FAS semi-empirically evaluated from small earthquakes for damaging earthquakes in Korea with maximum MMI ${\geq}$ VI could predict the observed MMI with the maximum error of 0.63 by using the combined FAS m-${\sigma}$ models of Korea for MMI ${\leq}$ IV and global region for MMI ${\geq}$ V.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.04a
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• pp.44-51
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• 1998

A seismic attenuation formula is derived from the intensity maps of medium sized four earthquakes that occurred in the southern part of Korean peninsula. In order to obtain the seismic attenuation formula, the the coefficients of four attenuation equations representing the intensity maps are integrated using the proper weighting factors depending on the credibility of the data are assigned to. The proposed formula shows the trend of attenuation similar to the ones for the Eastern North America for the region within the epicentral distance of 200km, but produces higher attenuation at farther distances. Though the attenuation curve is not derived from the instrumental data, the result could be a useful tool for the analysis of seismic hazard in Korean peninsula.

• Economic and Environmental Geology
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• v.32 no.6
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• pp.653-660
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• 1999

Any mechanical system has a natural oscillation which can be excited, and the earth is no exception. The earth can oscillate in an indefinite number of normal modes of oscillation, rather like a giant bell. The various free modes are generally sparated into two categoridal modes and toroidal modes. Clearly the toroidal modes will produce no perturvation of the gravity field and no vertical acceleration on the surface of the earth. Hence only spheroidal modes can be detected with a gravimeter. EarthTide gravimeter was installed at AIMST in order to observe free modes of the earth. Eight major earthquakes including chinese earthquake (magnitude 7.3) with free oscillations of the earth are observed during one year (1998. 8. 1∼1999.7.31). And then the earth tides components were eilminated from earthquake records using a numerical Butterworth highpass filter. Spectral analysis of gravity readings repersent that 48 observations of shheroidal modes. The relationships between instrumental observations and theoretical predictions based on the Gutenberg earth model agree well those resulting from free oscillation in Korea.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1989.10a
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• pp.46-50
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• 1989

Methods for the estimation of the coefficient matrices in the equation of motion for a linear multi-degree-of-freedom structure arc studied. For this purpose, the equation of motion is transformed into an auto-regressive and moving average with auxiliary input (ARMAX) model. The ARMAX parameters are evaluated using several methods of parameter estimation; such as toe least squares, the instrumental variable, the maximum likelihood and the limited Information maximum likelihood methods. Then the parameters of the equation of motion are recovered therefrom. Numerical example is given for a 3-story building model subjected to an earthquake exitation.

• Earthquakes and Structures
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• v.15 no.1
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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.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.3
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• pp.83-86
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• 1998

The results from the Individual Plant Examination of External Event of Yonggwyang nuclear power plants, unit 3 & 4, in Korea have shown that the high degree of diversities of the experts' opinions on seismicity and attenuation models is su, pp.sed to be generic cause of uncertainty of APEs(annual exceedance probability) in the PAHA(probabilistic seismic hazard analysis). This study investigated the sensitivity of the focal depth, which is one of the most uncertain seismicity parameters in Korea, Significant differences in resultant values of annual exceedance probabilities and much more symmetrical shape of the resultant PDFs(probability density functions), in case of consideration of focal depth, are found. These two results suggest that, even for the same seismic input data set including the seismicity models and ground motion attenuation models, to consider focal depth additionally for probabilistic seismic hazard analysis evaluation makes significant influence on the distributions of uncertainties and probabilities of exceedance per year for the whole ranges of seismic hazard levels. These facts suggest that it is necessary to derive focal depth parameter more effectively from the historical and instrumental documents on earthquake phenomena in Koran Peninsula for the future study of PSHA.

• 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.