• Geophysics and Geophysical Exploration
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• v.14 no.3
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• pp.254-260
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• 2011

We studied magnitude determination method using high-frequency energy radiation duration to calculate rapidly magnitude of large earthquakes that occurred around Japan. Fourteen earthquakes were analyzed using Korea Meteorological Administration (KMA) data. We calculated duration of high-frequency energy radiation with 2~4 Hz band pass filter at each data and estimated magnitude. As a result, duration becomes longer as magnitude becomes larger and the magnitude estimated using regional earthquake data are similar to that using teleseismic data. Therefore when an earthquake occurs around Japan we will be able to estimate the magnitude in a relatively short time using KMA data and it may be possible to determine if the earthquake is large enough to produce tsunami.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.09a
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• pp.44-51
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• 2001

We compare with earthquake parameters of KMA(Korea Meteorological Administration) and ISC(International Seismological Centre) to understand characteristics of earthquake using 30 earthquakes data acquired from 1978 to 1998 in Korea. We calculate difference of KMA between ISC epicentral distance and analyze for magnitude and year. Difference of epicentral distance decreases according to increase of magnitude and have no concern with year. That is the lowest in case of earthquake occurring in land of south Korea. We estimate relation formula for magnitude of KMA and ESC. The result can be expressed in KMA( $M_{L}$) and ISC( $m_{b}$ ) as $M_{L}$$^{KMA}$ = 0.70* $m_{b}$ $^{ISC}$+1.03 and in KMA( $M_{L}$) and ISC( $M_{L}$ as $M_{L}$$^{KMA}$=0.47* $M_{L}$$^{ISC}$+1.37X> ISC/+1.371.371.37

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1997.10a
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• pp.57-69
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• 1997

All of the Tsumami which affected severly the east coast of the Korean Peninsula in the years 1741-1993 are caused by earthquakes occurred along the boundary sea of Japan and norther Honshu. These earthquakes with magnitude greater than 7.0 are results of relative movement between the North American Plate and Urasian Plate. The active fault along the boundary of the two plates is attracted by many researchers since the 1983 May earthquake of magnitude 7.7. It is important to anticipate when the next large earthquake will occur and how much it affect the east coast of Korea. Among a few models of spatial seismic gap were proposed for earthquake occurrences accompanying Tsunami, Ishikawas' east-west seismic gap model is the most probable one. There is a tendency that the period between the activities of the active faults becomes shorter. It is expected that a large earthquake of magnitude 7.0 or above will occur along the eastern boundary of Japan Sea at the end of this century and produce Tsunami at the east coast of Korea.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.09a
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• pp.3-10
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• 2001

In order to establish the intensity-magnitude relation far the Korean earthquakes, those relations for the earthquakes in the Sino-Korean craton were estimated. In this process, earthquake data of northeastern China region whose geological environment is similar to Korea Peninsula were also utilized. These data were analyzed not only with linear fit, but also with non-linear fit. The fellowing relation, M=0.57 $\times$ 1$_{e}$ + 2.86, seems appropriate for the present, but its validity should be tested more in the future.e.

• Economic and Environmental Geology
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• v.34 no.6
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• pp.573-581
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• 2001

110 earthquake parameters (origin time, epicentral location and magnitude) were determined from 533 event records between 1905 and 1942 using data mainly from the "Annual Report of the Meteorological Observatory of the Government General of Tyosen" We adopted epicentral coordinates from the original reports for 34 events and from the Japanese Central Meteorological Observatory far another .34 events. We determined epicenters for 37 events using arrival time information from the reports. We adopted 4 epicenters from the International Seismological Summary and I from the Chinese bulletin. To determine the magnitude, we applied Tsuboi (1954) formula which is currently employed by Korea Meteorological Administration (KMA) for 94 events. For 16 events, we determined magnitude from the reef)reed felt epicentral areal using the correlation equation between known magnitude and felt area.

• Journal of the Earthquake Engineering Society of Korea
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• v.22 no.3
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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.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.09a
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• pp.28-34
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• 2002

The b-value in the magnitude-frequency relationship logN(m) = $\alpha$ - bmwhere N(m) is the number of earthquakes exceeding magnitude m, is important seismicity parameter In hazard analysis. Estimation of the b-value for earthquake data observed on KSRS array network is done employing the maximum likelihood technique. Assuming the whole Korea Peninsula as a single seismic source area, the b-value is computed at 0.9. The estimation for KMA earthquake data is also similar to that. Since estimate is a function of minimum magnitude, we can inspect the completeness of earthquake catalog in the fitting process of b-value. KSRS and KMA data lists are probably incomplete for magnitudes less than 2.0 and 3.0, respectively. Examples from probabilistic seismic hazard assessment calculated for a range of b-value show that the small change of b-value has seriously effect on the prediction of ground motion.

• Korean Journal of Remote Sensing
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• v.34 no.6_4
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• pp.1531-1544
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• 2018

We detected the coseismic ionospheric disturbance generated by the earthquakes of magnitude 5.0 and greater in Korean Peninsula. We considered the seismic events such as Gyeongju earthquake in September 2016 with magnitude 5.8, the Pohang earthquake in November 2017 with magnitude 5.4, and the underground nuclear explosion from North Korea in September 2017 with magnitude 5.7. Although all GPS stations were not detected, the ionospheric disturbance induced by these earthquakes occurred approximately 10-30 minutes and 40-60 minutes after the events. We inferred that the time difference within each variation is due to the different focal depth and the geometry of epicenter, satellite, and GPS station. In the case of the Gyeongju earthquake, the earthquake had relatively deeper depth than the other earthquakes. However, the seismic magnitude was bigger and it occurred at nighttime when the ionospheric activity was stable. So we could observe such anomalous variations. It is considered that the ionospheric disturbance caused by the difference in velocity of the upward propagating waves generated by earthquake appears more than once. Our results indicate that the detection of ionospheric disturbances varies depending on the geometry of the GPS station, satellite, and epicenter or the detection method and that the apparent growth of amplitude in the time series varies depending on the focal depth or the site-satellite-epicenter geometry.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.7_spc
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• pp.443-451
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• 2016

A Gyeongju earthquake in the magnitude of 5.8 on the Richter scale (the moment magnitude of 5.4), which was recorded as the strongest earthquake in Korea, occurred in September 12, 2016. Compared with the 2011 Virginia earthquake, the moment magnitude was slightly smaller and its duration was 3 seconds, much shorter than 10 seconds of the Virginia earthquake, resulting in relatively minor damage. But the two earthquakes are quite similar in terms of the overall scale, unexpectedness, and social situation. The North Anna Nuclear Power Plant, which is a nuclear power plant located at 18 km away from the epicenter of the Virginia earthquake, had no damage to nuclear reactors because the reactors were automatically shut down as the design basis earthquake value was exceeded. Ground accelerations of the 2016 Gyeongju earthquake did not exceed the threshold value but the manual shutdown was carried out so that Wolsong Nuclear Power Site was not damaged. Damaged historic homestead house and masonry structures due to the Virginia earthquake have been repaired, reinforced, and rebuilt based on a long-term earthquake recovery project. Likewise, it will be necessary to carefully carry out an earthquake recovery planning program to improve overall seismic performance and to reconstruct the historic buildings and structures damaged as a result of the Gyeongju earthquake.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.1
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• pp.9-19
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• 2016

Permanent deformation plays a key role in performance based earthquake resistant design. In order to estimate permanent deformation after earthquake, it is essential to secure reliable response history analysis(RHA) as well as earthquake scenario. This study focuses on permanent deformation of an inverted T-type wall under earthquake. The study is composed of two separate parts. The first one is on the verification of RHA and the second one is on an effect of input earthquake motion. The former is discussed in companion paper and the latter in this paper. In order to investigate the effect of an input earthquake motion on the permanent deformation, three bins of spectral matched real earthquake records with different magnitude, regions, epicentral distance are constructed. Parametric study was performed using the verified RHA through the companion paper for each earthquake records in the bins. The most influential parameter affecting permanent displacement is magnitude. The other parameters describing earthquake motion are not significant enough to increase permanent displacement of the inverted T-type wall except for energy related parameters(AI, CI, SEI).