• The Journal of Engineering Geology
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• v.5 no.3
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• pp.309-329
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• 1995

Seismicity and stress state in the Korean peninsula are studied using the catalogue of historical earthquakes and that from the seismological observations before the 1960s, with the aid of instrumental catalogue up to 1995. It seems that the completeness of the historical catalogue has a significant enhancement during the first two hundred years of the Yi dynasty, i.e., from the 1400s to the 1600s. From then on the catalogue may be regarded as near to complete for strong earthquakes in an overall sense. From the distribution of strong earthquakes, three seismic zones may be identified. From the south to the north, those are the southern seismic zone (남부지진대), the Seoul-Pyongyang seismic zone (서울-평양지진대), and the northern seismic zone (북부지진대). The mechanisms of some earthquakes obtained using first motion read- ings are reevaluated with a grid testing method. The results indicate that the compressional axis is nearly horizontal along the EW direction.

• Structural Engineering and Mechanics
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• v.49 no.3
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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.

• 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 Earthquake Engineering Society of Korea
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• v.19 no.5
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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.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1997.10a
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• pp.11-26
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• 1997

It has knows that the seismicity of the Korean Peninsula is relatively inactive than those of adjacent northern China and southwestern Japan. Recently the review of long term historical records and recent seismicity. In addition, it is considered that the modern society is more vulnerable to seismic hazard because of high urbanization and industrialization. From this viewpoint, the improvement and modification of the present regulation for aseismic design is strongly proposed. The purpose of the present study is to prepare seismic hazard maps for Korea to be used in improving the present regulation. The present study was performed as a cooperative project of eight Korean seismologists. Each seismologist calculated independently seismic hazard value at the given grid points based on his own judgement about methodology and seismicity. Then the values are unified with equal weight to produce a seismic hazard map. Seven seismic hazard maps for peak acceleration with 10 percentile probability of exceedance in 5, 10, 20, 50, 100, 250, 500 years are presented. This probability of exceedancd in such years corresponds to return period of 48, 95, 190, 475, 950, 2373, 4747 years, respectively. It is recommended to use a hazard map to be selected on the basis of the importance and the design level of structures.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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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.

• Geophysics and Geophysical Exploration
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• v.14 no.3
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• pp.242-248
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• 2011

By applying analytic method to the uniform model, the intrinsic and scattering quality factor ($Q_i^{-1}$ and $Q_s^{-1}$) was separated for the southeastern part of Korean Peninsula. The Multiple Lapse Time Window Analysis method was used to fit theoretical values with observations obtained 759 earthquake data. While previous study for the Korean Peninsula showed very low $Q_i^{-1}$ and $Q_s^{-1}$ reflecting inactive seismicity, southeastern Korea exhibited relatively high $Q_i^{-1}$ and $Q_s^{-1}$ values interpreted as higher seismicity than the other region in the peninsula.

• Earthquakes and Structures
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• v.20 no.4
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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.

• Geophysics and Geophysical Exploration
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• v.13 no.3
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• pp.256-267
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• 2010

Earthquakes in the Korean Peninsula occur along the faults formed and boundaries between major geological units ruptured due to violent tectonic activities during the Mesozoic. E-W and/or ENE-SSW compressive stress regime resulting from collisions between the Eurasian plate and neighbouring the Indian plate, the Pacific plate and the Philippine plate trigger Korean earthquakes of thrust faulting with predominant strike-slip components along the mostly NNE-SSW trending active faults. Seismicity of the Korean peninsula has been moderate to low during the past 20 centuries except for the period from the 15th to the 18th centuries of exceptionally high seismicity, showing the typical irregularity of intraplate seismicity. The structure of the Korean peninsula is rather homogeneous without the Conrad discontinuity sharply dividing the upper and lower crust. Lateral heterogeneities exist in the crust. The crust with an average thickness of about 33 km is thicker in the mountainous region than the plain due to the Airy-type isostatic equilibrium maintained in the peninsula. Crustal P-wave velocity with average of about 6.3 km/sec increases gradually from the near surface to the Moho. The upper mantle P-wave (Pn) velocity is about 7.8 km/sec.

• Journal of the Korean earth science society
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• v.40 no.3
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• pp.272-282
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• 2019

Although the knowledge of current seismicity is a critical information for making and implementing effective earthquake-related policy, the detailed seismicity information of the metropolitan areas with high-population density has been largely underestimated due to the high-level of cultural noise and small earthquake magnitude. This study presents 12 earthquakes including 2 earthquakes previously known and 10 additional earthquakes occurred from 2010 to 2017 in Busan, but they were unreported by the Korea Meteorological Administration. Matched filter technique is used to detect micro-earthquakes. Although the epicenters of micro-earthquakes though present a distinguished linearity, a correlation with faults in the area is unknown. A repeated micro-seismicity suggests that there are subsurface structures responsible for observed events. If large earthquakes occur along the fault in Busan, they may cause catastrophic natural disasters. Given the fact that the recent earthquakes did not accompany any surface signatures, it is highly recommended that the current micro-seismicity be investigated, and updated seismicity information be incorporated into establishing active fault maps in Korea.