• Journal of the Korean earth science society
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• v.42 no.1
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• pp.55-64
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• 2021

Tephrochronology is the study of tephra layers to correlate and date geologic events. As tephra layers can be used as time-markers, they are essential for the dating of Quaternary deposits. In this study, two types of tephra layers were found in the upper and lower parts of marine terrace deposits distributed in the Sanha-dong and Jeongja-dong, Ulsan areas. Based on the morphological features of glass shards, refractive indices, major element compositions, and similarity coefficients, the upper and lower tephras were identified as AT (ca. 25 ka) and Ata (ca. 105-110 ka) tephra, respectively. To the best of our knowledge, this is the first official report of Ata tephra on terrestrial deposits in Korea. These results are expected to aidin the research of the Quaternary paleoclimate, paleoenvironment, and active faults in the southeastern part of Korea.

• The Journal of the Petrological Society of Korea
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• v.22 no.4
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• pp.273-289
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• 2013

Fallout ash is a notorious hazard that can have a variety of damages on agriculture and infrastructure and, most notably to aviation and human health. This study discusses the design of a conceptual model to aid in modeling the dispersal and deposition of ash from Mt. Baekdu volcano. It includes a discussion of assumptions and boundary conditions of the model as well as a detailed diagram of the conceptual model, complete with input parameters, units and equations. The two main processes contained within the model are the dispersal and deposition of ash, the outputs obtained from running the model, if designed, would be the total amount of fine ash contained in the eruption column, distance travelled by ash and ash thickness at surface.

• Journal of the Mineralogical Society of Korea
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• v.23 no.2
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• pp.141-150
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• 2010

Basaltic ash of Udo tuff cone, Jeju Island, was almost fresh across strata, but significantly altered toward surface by supergene process. The supergene alteration of the Udo tuff was examined by using X-ray diffraction, scanning and transmission electron microscopy, and electron microprobe analysis for elucidating the alteration process of basaltic ash in terrestrial environments. Fresh ash particles were composed of glass matrix, plagioclase, olivine, and pyroxene. The glass matrix was selectively replaced inward by colloform alteration rinds of Fe-Ti-rich amorphous silicate nanogranules and smectite, often leaving glass core at the center of larger ash particles. Some of the dissolved species released from the altered ash particle precipitated as fine honycomb aggregates of smectite on the pore walls, contributing to the cementation and lithification of volcanic ash.

• Journal of the Korean earth science society
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• v.38 no.2
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• pp.115-128
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• 2017

Aso caldera volcano is located in central Kyushu, Japan which is one of the largest caldera volcanoes in the world. Nakadake crater is the only active central cone in Aso caldera. There was an explosive eruption on October 8, 2016, the eruption column height was 11 km, and fallout ash was found 300 km away from the volcano. In this study, we performed a numerical simulation to analyze the ash dispersion and the fallout tephra deposits during this eruption using Ash3D that was developed by the United States Geological Survey. The result showed that the ash would spread to the east and northeast, that could not affect the Korean peninsula, and the volcanic ash was deposited at a place from a distance of 400 km or more in the direction of east and northeast. The result was in close agreement with the identified ashfall deposits. Ash3D can be useful for quick forecast for the effects of hazards caused by volcanic ash.

• Korean Journal of Remote Sensing
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• v.30 no.1
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• pp.47-59
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• 2014

Volcanic ash (VA) can be estimated by remote sensing sensors through their spectral signatures determined by the inherent optical property (IOP) including complex refractive index and the scattering properties. Until now, a very limited range of VA refractive indices has been reported and the VA from each volcanic eruption has a different composition. To improve the robustness of VA remote sensing, there is a need to understanding of VA - radiation interactions. In this study, we calculated extinction coefficient, scattering phase function, asymmetry factor, and single scattering albedo which show different values between andesite and pumice. Then, IOPs were used to analyze the relationship between theoretical remote sensed radiation calculated by radiative transfer model under various aerosol optical thickness (${\tau}$) and sun-sensor geometries and characteristics of VA. It was found that the mean rate of change of radiance at top of atmosphere versus ${\tau}$ is six times larger than in radiance values at 0.55 ${\mu}m$. At the surface, positive correlation dominates when ${\tau}$ <1, but negative correlation dominates when ${\tau}$ >1. However, radiance differences between andesite and pumice at 11 ${\mu}m$ are very small. These differences between two VA types are expressed as the polynomial regression functions and that increase as VA optical thickness increases. Finally, these results would allow VA to be better characterized by remote sensing sensors.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.16 no.1
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• pp.166-175
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• 2017

Hazardous volcanic activity will continue to occur in the ring of fire, a major area in the basin of the Pacific Ocean where a large number of earthquakes and volcanic eruptions occur. and, because of rising populations, development pressures, and expanding national and international air traffic over volcanic regions, risks to life and property through exposure to volcano hazards continue to increase. During an eruption, volcanic contamination can reach and exceed the cruising altitudes of turbine-powered aircraft, among others, within minutes and spread over vast geographical areas within a few days. Volcanic ash can affect the operation of aircraft at aerodromes. Volcanic ash deposition at an aerodrome, even in very small amounts, can result in the closure of the aerodrome until all the deposited ash has been removed. In this study, air traffic information framework is presented along with algorithms to define affected routes, waypoints and airports using GIS geometry analysis.

• The Journal of the Petrological Society of Korea
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• v.27 no.1
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• pp.17-24
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• 2018

The volcanic history of the volcanic ash cloud movement recorded in the annals of the Choson dynasty in 1654, presumably due to explosive eruptions from Mt. Baekdu volcano. On October 21, 1654, volcanic ash and volcanic gas erupted from Mt. Baekdu could be interpreted as volcanic ash, which was transported to low altitude by winds of north and northeast winds and descended to the south of the peninsula along with volcanic ash clouds. The affected area appeared northward in the southern boundary of Hamgyeongdo, which is estimated to have moved the volcanic ash from Mt. Baekdu to the south of the Korean peninsula. Clouds of volcanic ash have passed through Jeokseong and Jangdan area, Gyeonggido about 500 km away from Mt. Baekdu. This is interpreted as a result of the formation of a volcanic ash cloud along the ground in a curved shape due to the influence of the prevailing wind, which was formed by Plinian-type eruption at Mt. Baekdu. This is reproduced by numerical simulations on the similar weather pattern model.

• Journal of the Korean earth science society
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• v.33 no.3
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• pp.280-293
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• 2012

In order to clarify the characteristics of dispersion of volcanic tephra emitted from the Mt. Baegdu with various eruption environment, numerical analysis were performed using numerical models, Weather Research and Forecast (WRF) and FLEXPART. Synoptic conditions at 12 October 2010 was adopted because the volcanic ash of Mt. Baegdu can reach the Korean peninsula and its dispersion pattern was compared with different Volcanic Explosivity Index (VEI) and particle size. Predominant size of falling out ash flowing in the peninsular is smaller than 0.5 mm and the ash large than the size is difficult to get in the peninsular due to the its weak ability of truculent diffusion. the difference of ash distribution with various VEI scenarios is not so much but number density of ash in the air is dramatically changed. Volcanic ash tends to be deposited easily in eastern coastal area such as Gangneung and Busan, because of the inflow of ash from East Sea and barrier effect of the Taeback mountains along the east coast of the Korean Peninsula. Accumulated amount of ash deposition can be increased in short period in several urban areas.

• Journal of The Geomorphological Association of Korea
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• v.25 no.1
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• pp.97-113
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• 2018

Low-frequency geological natural disaster events such as Pohang earthquake have been occurred. As a results, there's a growing recognition on the importance of education and training for low frequency geological disasters in Korea. In spite of many years of scientific researches on volcanic disaster prevention and preparedness on Baekdusan volcano, the results do not provide the proper scenario for the training for volcanic ash event. Fall 3D volcanic ash diffusion model was run based on wind field data for the last five year, assuming Aso Mountain's explosion with volcanic explosion index 5 for seventy two hours. The management criteria values for proper actions in the previous studies were applied to make a scenario for thirteen groups of the disaster response teams such as train transportation, water supply, electrical facilities and human health. The models on the relationship between education and training for disaster prevention and response were suggested to fulfill the scientific and practical training at local level.

• The Journal of Engineering Geology
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• v.28 no.2
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• pp.267-276
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• 2018

Volcanic ash from volcanic eruptions spreads to vast areas hundreds of kilometers away, and when volcanic ash flows into surface waters, it will be damaged by water supply. In case of water supply facilities, it provides to people drinking water and domestic water, be consumed by the people cause social disorder when water supply is cut off due to damage such as water pollution caused by harmful materials of volcanic ash. However, when we looked at the disaster management manual, the establishment of a water supply facility manual to deal with the damage of volcanic ash was found to be insufficient. Therefore, in this study, the existing volcanic and water pollution related manuals were analyzed and problems were derived. In order to make quick situation judgment and response activities, we have suggested the scope of the water supply facility manual, disaster type, major missions and system of related organizations, and scenario of crisis situation by disaster type.