• Journal of Astronomy and Space Sciences
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• v.37 no.1
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• pp.61-68
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• 2020

Recent studies have suggested that detectable ionospheric disturbances precede earthquakes. In the present study, variations in the vertical total electron content (TEC) for eight earthquakes with magnitudes of M ≥ 5.5 in the western United States were investigated during the solar maximum of 2013-2015 using United States total electron content (US-TEC) data provided by the National Oceanic and Atmospheric Administration. Analyses of 12 earthquakes with magnitudes of 5.0 ≤ M < 5.5 in the same region were also performed. The TEC variations were examined for 40 days, including the times when the earthquakes occurred. The results indicated a correlation between earthquakes with magnitudes of M ≥ 5.0 and ionospheric TEC anomalies. TEC anomalies occurred before 60% of the earthquakes. Additionally, they were more frequently observed for large earthquakes (75%, M ≥ 5.5) than for small earthquakes (50%, 5.5 > M ≥ 5.0). Anomalous increases in the TEC occurred 2-18 days before the earthquakes as an ionospheric precursor, whereas solar and geomagnetic activities were low or moderate.

• Nuclear Engineering and Technology
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• v.50 no.3
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• pp.494-503
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• 2018

As public acceptance of nuclear energy in Korea worsens due to the Fukushima accident and the earthquakes that occurred in the Gyeongju area near the Wolsong nuclear power plant (NPP), estimating the effects of earthquakes has become more essential for the nuclear industry. Currently, most countermeasures against earthquakes are limited to large-scale disasters. Minor-scale earthquakes used to be ignored. Even though people do not feel the shaking due to minor earthquakes and minor earthquakes incur little damage to NPPs, they can change the environmental conditions, for instance, underground water level and the conductivity of the groundwater. This study conducted a questionnaire survey of residents living in the vicinity of an NPP to determine their perception and acceptance of plant safety against minor earthquakes. The results show that the residents feel earthquakes at levels that can be felt by people, but incur little damage to NPPs, as minor earthquakes (magnitude of 2.0-3.9) and set this level as a standard for countermeasures. Even if a minor earthquake has little impact on the safety of an NPP, there is still a possibility that public opinion will get worse. This study provides analysis results about problems of earthquake measures of Korean NPPs and specific things that can bring about an effect of deterioration of public acceptance. Based on these data, this article suggests that active management of minor earthquakes is necessary for the sustainability of nuclear energy.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.366-368
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• 2003

The Rann of Kachchh in Gujarat in the Western part of India is seismically the most active area outside Himalayan Belt. Several severe earthquakes of which the 1819 Rann of Kachchh and 2001 Bhuj Earthquakes are the severest recorded have rocked the region. This paper is an attempt to make a comparative study of the 1819,1844 and 2001 earthquakes. The study of 1819 and 1944 earthquakes is based on secondary accounts while 2001 Bhuj earthquake is based on remote Sensing. From a comparative study of the three earthquakes many interesting conclusions can be drawn. These earthquakes have been the result of accumulation of stress caused due to the collision of Indian Plate with the Eurasian Plate, which is continuously moving northwards. The earthquakes have been felt over large part of the Indian Sub-continent. These have resulted in creation of several faults that have activated periodically. Prominent of them are the Allah Bund Fault, Manfara Fault and Budharmora Fault. These are strike slip faults that get periodically activated. In future too these faults are going to be the most vulnerable to any seismic activity with the probability of high intensity earthquakes occurring along them in future too.

• Journal of Soil and Groundwater Environment
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• v.21 no.6
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• pp.80-86
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• 2016

Earthquakes of M5.1, M5.8 and M4.5 occurred in September 12 and 19 respectively in Gyeongju, Gyeongbuk Province. Theses earthquakes inflated fears of people and highlighted necessity of detailed countermeasures because we have considered our country is safe to earthquakes. In the meanwhile, earthquake also impacts groundwater and thus it was recently reported that the Gyeongju Earthquakes affected groundwater there. This study evaluates daily groundwater data collected from five national groundwater monitoring stations (Geoncheon, Sannae, Oedong, Yangbuksin, Cheonbuk) in Gyeongju. The analysis revealed that only groundwater level of bedrock monitoring well hosted in andesite exhibited earthquake impact while no wells in the other four stations hosted in sedimentary rocks showed substantial responses to the earthquakes. This may be derived from the difference of seismic velocity of hosting rocks as well as epicenter distance. Special interest on groundwater monitoring is required to predict earthquakes as precursory phenomena.

• Nuclear Engineering and Technology
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• v.50 no.3
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• pp.512-518
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• 2018

This article measured and analyzed the indoor radon concentrations at one university building in Gyeongju, Republic of Korea, to investigate if there is any relationship between earthquakes and indoor radon concentration. Since 12 September 2016, when two 5.1 and 5.8 magnitude earthquakes occurred, hundreds of aftershocks affected Gyeongju until January 2017. The measurements were made at the ground floor of the Energy Engineering Hall of Dongguk University in Gyeongju over a period between February 2016 and January 2017. The measurements were made with an RAD7 detector on the basis of the US Environmental Protection Agency measurement protocol. Each measurement was continuously made every 30 minutes over the measurement period every month. Among earthquakes with 2.0 or greater magnitude, the earthquakes whose occurrence timings fell into the measurement periods were screened for further analysis. We observed similar spike-like patterns between the indoor radon concentration distributions and earthquakes: a sudden increase in the peak indoor radon concentration 1-4 days before an earthquake, gradual decrease before the earthquake, and sudden drop on the day of the earthquake if the interval between successive earthquakes was moderately longer, for example, 3 days in this article.

• Earthquakes and Structures
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• v.24 no.5
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• pp.377-391
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• 2023

The high seismic risk has once again revealed in Türkiye with two major earthquakes that occurred on 06.02.2023, which took its place among the most destructive earthquakes in the last century. Totally, 65 earthquakes that occurred in the historical period in Türkiye were taken into account within the scope of this study. The seismic parameters were compared by considering the last two earthquake hazard maps for the epicenters of these earthquakes. Earthquake Intensity (I) of historical earthquakes were converted to Peak Ground Acceleration (PGA) by using suggested relations. Structural analyzes were performed for a sample reinforced-concrete building by using the obtained PGA's and predicted PGA's in the last two earthquake hazard maps. In the structural analysis, two different material groups such as low (C12-S220) and normal (C25-S420) were selected. As the material strength increased, the period value decreased, while the seismic capacity and stiffness increased. It has been determined that there are differences between the measured and proposed seismic risks for some earthquakes, and as a result, there are significant differences between the expected target displacement values from the structures. Therefore, it will not be possible to estimate the damage and to determine the building performance realistically. The main purpose of the study is to reveal whether the earthquake risk is adequately represented on seismic and structural parameters.

• Journal of Industrial Technology
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• v.25 no.A
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• pp.31-38
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• 2005

Recent earthquakes have shown that near-field earthquakes can produce spectral demands significantly larger than those considered in current design code. International Atomic Energy Agency (IAEA) has recently initiated a coordinated research program on safety significance of near-field earthquakes. The purpose of this program is to focus on the assessment of vulnerability of nuclear facility structures by using and adapting the best available engineering practices appropriate to evaluate the effects of near-field earthquakes. The objective of this paper is to evaluate of seismic responses of a shear building test specimen subjected to near-filed earthquakes. To achieve the objective, the seismic responses of the test specimen, evaluated by the Displacement Coefficient Method (DCM) and Nonlinear Dynamic Analysis (NDA), are compared with those by the experimental tests.

• Earthquakes and Structures
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• v.17 no.4
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• pp.355-363
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• 2019

Masonry structures in the rural areas of Turkey often damaged due to moderate and big earthquakes. After every earthquake many scientists made field investigations on the earthquake performance of these structures and gave many useful information on construction techniques. However, the newly constructed masonry buildings are still not suitable for the suggested techniques, and they are still in danger against future earthquakes. Five moderate earthquakes of moment magnitude Mw 5.3, 5.3, 5.2, 5.0, and 5.3 struck the Ayvacik-Çanakkale District of Turkey between 6 and 12 February, 2017. More than a thousand of aftershocks were occurred and most of the masonry buildings in the villages nearby main shock epicenter were affected. The author went to the earthquake field and investigated the earthquake performances of masonry structures. This paper presents the recorded acceleration data, acceleration response spectra, and the seismological aspects of these earthquakes. Besides, case studies of damaged stone masonry buildings, and failure mechanisms are discussed with illustrated photos which were taken during the field investigations. It is concluded that the damaged masonry buildings were not designed and constructed properly in accordance with the Turkish building codes or similar specifications.

• Structural Engineering and Mechanics
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• v.47 no.1
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• pp.99-118
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• 2013

Earthquakes, which are unavoidable natural phenomena in Turkey, have often produced economic and social disaster. The latest destructive earthquakes happened in Van city. Van, Turkey, earthquakes with M = 7.2 occurred on 23 October 2011 at 13:41 (local time), whose epicenter was about 16 km north of Van (Tabanlivillage) and M = 5.6 on 9 November 2011 epicentered near the town of Edremit south of Van in eastern Turkey and caused the loss of life and heavy damages. Both earthquakes killed 644 people and 2608 people were injured. Approximately 4000 buildings collapsed or were seriously damaged. The majority of the damaged structures were seismically insufficient, unreinforced masonry and adobe buildings in rural areas. In this paper, site surveys of the damaged masonry and adobe buildings are presented and the reasons for the caused damages are discussed in detail.

• Earthquakes and Structures
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• v.17 no.3
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• pp.317-327
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• 2019

High-speed railway bridge piers in seismically active area may be subjected to multiple earthquakes and then produce cumulative residual deformation. To study the cumulative residual deformation of high-speed railway bridge piers under multiple earthquakes, a nonlinear numerical analytical model with multi-DOF (MDOF) system is presented and validated against two shaking table tests in this paper. Based on the presented model, a simple supported beam bridge pier model of high-speed railway is established and used to investigate the cumulative residual deformation of high-speed railway bridge pier under mainshock-aftershock sequences and swarm type seismic sequences. The results show that the cumulative residual deformation of the bridge pier increases with earthquake number, and the increasing rates are different under different earthquake number. The residual deformation of bridge pier subjected to multiple earthquakes is accumulated and may exceed the limit of code.