• Journal of the Korean earth science society
• /
• v.43 no.1
• /
• pp.165-175
• /
• 2022

Earthquakes have occurred owing to movements on a fault since several billion years ago. Research on the relationship between earthquakes and groundwater began in the 1960s in the United States, but related works, including hydrogeochemistry research, only began in the 2010s in South Korea. In this study, domestic studies on the relationship between earthquakes and groundwater until 2021 were collected from the Web of Science and characterized by subject area (groundwater level, hydrogeochemistry, combination of the two, and others). The results showed that the number of published articles per year was positively correlated with the 2011 Tohoku earthquake, 2016 Gyeongju earthquake, and 2017 Pohang earthquake, with the maximum numbers observed in 2011, 2018, 2019, and 2020. Most studies on the relationship between earthquakes and groundwater level addressed groundwater level fluctuations in the duration of the subject earthquake, with little consideration of the precursors. Groundwater level monitoring data, as well as hydrogeochemical information and microbial communities, may contribute to a more detailed understanding of groundwater flow and chemical reactions in bedrock caused by earthquakes. Therefore, the establishment of a national groundwater monitoring network for seismic monitoring and prediction is required.

• Geophysics and Geophysical Exploration
• /
• v.25 no.3
• /
• pp.109-119
• /
• 2022

The computational efficiency of reverse time migration (RTM) based on numerical modeling is not secured due to the high-frequency band of several hundred Hz or higher for data acquired through a three-dimensional (3D) ultra-high-resolution (UHR) seismic survey. Therefore, this study develops an RTM program to derive high-quality 3D geological structures using UHR seismic data. In the traditional 3D RTM program, an excitation amplitude technique that stores only the maximum amplitude of the source wavefield and a domain-limiting technique that minimizes the modeling area where the source and receivers are located were used to significantly reduce memory usage and calculation time. The program developed through this study successfully derived a 3D migration image with a horizontal grid size of 1 m for the 3D UHR seismic survey data obtained from the Korea Institute of Geoscience and Mineral Resources in 2019, and geological analysis was conducted.

• Ecology and Resilient Infrastructure
• /
• v.10 no.4
• /
• pp.97-106
• /
• 2023

This study analyzed morphological changes in the Singwangcheon and Naengcheon streams in Pohang caused by flooding due to Typhoon Hinnamnor. Analysis of the changes in river channel area from the past to recent times using aerial photos and drone-taken images showed that the river width had gradually decreased since the 1960s. However, after the flood, the river width increased again. Changes in the river cross-section before and after the flood show that a large amount of coarse sediment was deposited inside the river bend while the outer bank was eroded. The water levels calculated using HEC-RAS for the pre-flood cross-section based on the flood frequency discharges and estimated discharge from Oer Reservoir were significantly lower than the observed water level, which means that the cross-sectional change was not considered. The results of this study suggest that it is necessary to consider cross-sectional changes due to sediment transport when estimating the flood level of small and medium-sized mountain streams, and it is needed to investigate the geomorphic changes after floods.

• Journal of the Society of Disaster Information
• /
• v.17 no.4
• /
• pp.694-709
• /
• 2021

Purpose: In this study, earthquake-induced landslide risk assessment was conducted to provide basic data for efficient and preemptive damage prevention by selecting the erosion control work before the earthquake and the prediction and restoration priorities of the damaged area after the earthquake. Method: The study analyzed the previous studies abroad to examine the evaluation methodology and to derive the evaluation factors, and examine the utilization of the landslide hazard map currently used in Korea. In addition, the earthquake-induced landslide hazard map was also established on a pilot basis based on the fault zone and epicenter of Pohang using seismic attenuation. Result: The earthquake-induced landslide risk assessment study showed that China ranked 44%, Italy 16%, the U.S. 15%, Japan 10%, and Taiwan 8%. As for the evaluation method, the statistical model was the most common at 59%, and the physical model was found at 23%. The factors frequently used in the statistical model were altitude, distance from the fault, gradient, slope aspect, country rock, and topographic curvature. Since Korea's landslide hazard map reflects topography, geology, and forest floor conditions, it has been shown that it is reasonable to evaluate the risk of earthquake-induced landslides using it. As a result of evaluating the risk of landslides based on the fault zone and epicenter in the Pohang area, the risk grade was changed to reflect the impact of the earthquake. Conclusion: It is effective to use the landslide hazard map to evaluate the risk of earthquake-induced landslides at the regional scale. The risk map based on the fault zone is effective when used in the selection of a target site for preventive erosion control work to prevent damage from earthquake-induced landslides. In addition, the risk map based on the epicenter can be used for efficient follow-up management in order to prioritize damage prevention measures, such as to investigate the current status of landslide damage after an earthquake, or to restore the damaged area.

• Journal of International Area Studies (JIAS)
• /
• v.18 no.3
• /
• pp.109-144
• /
• 2014

In 2010, large areas of European airspace were closed by the volcanic ash generated by the eruption of Icelandic volcano and it disrupted global trade, business and travel which caused a huge economic damage on the air transport industry. This brought concerned about the economic impact by the eruption of Mt. Baekdu volcano. In this paper, we analyze the affected areas of the air transport industry were decided by calculating the PM10 density of volcanic ash changed over time and by determining the safe upper limit of ash density in their airspace. We separate the sales in the air transport industry according to each airline, airport, and month to estimate the direct losses when all flights inside a restricted zone were canceled. Also, we estimate the indirect losses in regional output, income, and value-added of the different major industries using interindustry (input-output) analysis. There is no direct damage from VEI 1 to VEI 5. But when VEI is 6, all flights to and from Yangyang airport will be canceled due to the No Fly Zone. And some flights to and from the airports Gimhae, Ulsan and Pohang will be restricted due to the Time Limited Zone. When VEI is 7, Yangyang, Gimhae, Ulsan, Pohang and Daegu airports will be closed and all flights will be canceled and delayed. During this time, the total economic losses on the air transport industry are estimated at 8.1 billion won(direct losses of about 3.55 billion won, indirect losses of about 4.57 billion won). Gimhae international airport accounted for 92% of the total loss and is the most affected area according to the volcanic ash scenario of Mt. Baekdu.

• Water for future
• /
• v.18 no.2
• /
• pp.163-174
• /
• 1985

This study aims at the development of a technique for the optimal water allocation by applying Dynamic Programming Model for the effective usage and rational allocation of water resources, in case of which limited water resources in river basin should be used in several stages. In analytical procedure the possible allocable area was firstly zoned into the four areas: Pohang area ($C_1$), Yeungcheon area ($C_2$), Gyeungsan area ($C_3$), Daegu area ($C_4$), which are located between the Yeongcheon dam and the confluence of the lower Kumho river and the main course of the Nakdong river. Secondly, a return function was determined on the basis of the correlation between the GRP in each area and the amount of water used to it. A DP Model, finally, was applied to the allocation of the water resources according to both their usage and the areas. As a result, the fact has been found that when allocating by the area, $C_1$ could be possibly supplied only with the water resources avaiable from the Yeungchon dam, and the maximum units supplied to $C_1$ should be 240 units ($1unit=10^3㎥$ per day), beyond which we ought to develop an alternative water resources. Also, the return from the allocation by the usage exceeded the one from it by the area. At the same time it was more profitable to limit the water supply to $C_1$ into 217 units. In the allocation by the area 240 units and 80 units, if only the water resources available from the Yeungcheon dam used, and 360 units and 80 units if the Doil dam used additionally, could be supplied to $C_1$ and the lower region respectively. In the allocation by the usage 103 units for industrial water with 33 units for both domestic and commercial water and 183 units, if only the water resources available from the Yeungcheon dam used, and 103 units with 33 units and 304 units, if the Doil dam taken into consideration additionally, could be supplied to $C_1$ and the lower region respectively. Therefore, much more water could be allocated to the region of lower Kumho river if the method of water allocation by the usage.

• Korean Journal of Soil Science and Fertilizer
• /
• v.16 no.2
• /
• pp.203-209
• /
• 1983

The occurrence and regional distribution of low temperature and drought during rice cropping period in Korea were studied to characterize the climatic impacts. The long term changes in rice yield, air temperature and precipitation were analyzed, and regional distributions were characterized. The significant climatic impacts on rice yield were heavy rain or flood, drought and low temperature. Since 1910, the occurrence of drought was 29 times, that of flood was 24 times and that of low temperature was 9 times; however, the drought and flood damages were decreased due to expansion of irrigation system since 1970 but low temperature damage was remarkedly increased. The long term changes in air temperature since 1908 in Suweon showed that the 5-year moving average from July to August decreased while that from May to June increased. The occurrence probability of the long term and early term low temperature types were the greatest in Korea and were in order of Suweon, Daegu and Kwangiu. The long term changes in 10-year moving average precipitation from April to June showed a 15 year cycle and recent years were in low precipitation period. The drought frequencies were the highest in Daegu and Pohang area. According to the precipitation from April to June and resevtoir storage at late June, the severest dry area were the Youngnam inland and the southwest coastal area.

• 한국해양학회지
• /
• v.27 no.1
• /
• pp.46-54
• /
• 1992

An investigation on the benthic polychaete community in Youngil Bay was conducted during four seasons of 1991. Polychaetes. the dominant macrofaunal group occupying 71.3% in total macro-faunal density, comprised a total of 72 species with a mean density of 1,485 indiv. m/SUP -2/. The highest species number of 54 spp. and density of 3,207 undiv. m/SUP -2/ was recorded in summer, while the lowest in autumn. The most abundant species was Spiophanes nombyx (37.5%), followed by Pseudopolydora sp.(8.4%), Lumbrineris longifolia(7.0%), Madden cristata(6.5%), Polydora ciliata(4.9%) and so on. Maldane cristata was dominated in winter, Polydora ciliata in spring and Spiophanes bombyx in summer and autumn. The density and species number of Polychaetes were high in the southeastern area of Youngil Bay, and poor near the mouth of Hyoungsan River. Based on the species composition, study area was divided into three regions. Each region sustained its specific benthic faunal assemblage; Maldane-Praxillella assemblage from the middle to the southeastern region of Youngil Bay, Spiophanes-Nephtys assemblage in the northwestern region, and Pseudopolydora-Polydora-Capitella assemblage from the mouth of Hyoungsan River to Pohang Hobour. Maldane Praxillella assemblage showed the highest species number of 55 spp.. and the highest species diversity and species richness indices. Spiophanes-Nephtys assemblage had the highest density of 2,675 indiv. m/SUP -2/ and the highest dominance index because of the predominance of Spiophanes bombyx with a density of 2,073 indiv. m/SUP -2/. Pseudopolydora-Polydora-Capitella assemblage was found in the polluted area and it was a specific assemblage mainly composed of the dominance of organic pollution indicator species. The dominant Polychaetes were Pseudopolydora sp., Polydora ciliata, Capitella capitata, and Dorvillea sp.

• Korean Journal of Environmental Biology
• /
• v.28 no.1
• /
• pp.30-39
• /
• 2010

We researched community structure, species composition, and habitat environment of Dendropanax morbifera populations distributed in Goheung, Haenam, Wando (I.), and Bogildo (I.) at south coast of the Korean Peninsula. Our research was also estimated possible area for growth of Dendropanax morbifera by analyzing meteorological factors of the habitat thereof. Dendropanax morbifera community divided into Castanopsis cuspidata var. sieboldii group and Carpinus laxiflora group by difference of species composition. Broad-leaved evergreens showed high dominance value in view of rNCD in Dendropanax morbifera community as follows: Camellia japonica (100.0), Quercus acuta (88.6), Castanopsis cuspidata var. sieboldii (55.8), Dendropanax morbifera Lev. (41.4), Trachelospermum asiaticum var. intermedium (23.8), Eurya japonica (19.9) and Ligustrum japonicum (11.5). In the population distribution, 94.2% of Carpinus laxiflora group consisted of sapling and small size class that are less than 5 cm in DBH while 54.2% of Castanopsis cuspidata var. sieboldii group did. The soil environment of habitat showed low soil acidity, good organic matter and water content, and good drainage. The distribution area of Dendropanax morifera habitat had $13^{\circ}C$ or more in annual mean temperature, $7.4^{\circ}C$ or more in daily minimum temperature, $100^{\circ}C$ month or more in warmth index, and approximately 1,344 mm in mean annual precipitation. Dendropanax morifera habitat corresponded to evergreen broad-leaved forest zone located in islands and coast in the southwest region of the Korean Peninsula. The northern limit line of Dendropanax morifera community was determined as Gunsan-Jeongeup-Gwangju-Jinju-Pohang-Youngdeok line based on $13^{\circ}C$ in annual mean temperature that was confirmed in natural habitat of Dendropanax morifera community.

• Journal of the Korean GEO-environmental Society
• /
• v.20 no.5
• /
• pp.5-12
• /
• 2019

On November 15, 2017, a unpredictable liquefaction damage was occurred at the $M_L=5.4$ Pohang earthquake and after, many researches have been conducted in Korea. In Korea, where there were no cases of earthquake damage, it has been extremely neglectable in preparing earthquake risk maps and building earthquake systems that corresponded to prevention and preparation. Since it is almost impossible to observe signs and symptoms of drought, floods, and typhoons in advance, it is very effective to predict the impacts and magnitudes of seismic events. In this study, 14,040 borehole data were collected in the metropolitan area and liquefaction evaluation was performed using the amplification factor. Based on this data, liquefaction hazard maps were prepared for ground accelerations of 0.06 g, 0.14 g, 0.22 g, and 0.30 g, including 200years return period to 4,800years return period. Also, the correlation analysis between the earthquake acceleration and LPI was carried out to draw a real-time predictable liquefaction hazard map. As a result, 707 correlation equations in every cells in GIS map were proposed. Finally, the simulation for liquefaction risk mapping against artificial earthquake was performed in the metropolitan area using the proposed correlation equations.