• Journal of the Korean earth science society
• /
• v.42 no.6
• /
• pp.688-699
• /
• 2021

On September 23, 2020, at 1:39 a.m., a bright fireball above Seocheon was observed across the country. Two fireball explosions were identified in the images of the All-Sky Camera (ASC), and the shock waves were recorded at seismic and infrasound stations in the southwestern Korean Peninsula. The location of the explosion was estimated by a Bayesian-based location method using the arrival times of the fireball-associated seismic and infrasound signals at 17 stations. Realistic azimuth- and rang-dependent propagation speeds of sound waves were incorporated into the location method to increase the reliability of the results. The location of the sound source was found to be 36.050°N, 126.855°E at an altitude of 35 km, which was close to the location of the second fireball explosion. The two explosions were identified as sequential infrasound arrivals at local infrasound stations. Simulations of waveforms for long ranges explain the detection results at distant infrasound stations, up to ~266 km from the sound source. The dominant period of the signals recorded at five infrasound stations is about 0.4 s. A period-energy relation suggests the explosion energy was equivalent to ~0.3 ton of TNT.

• Journal of the Korean Geographical Society
• /
• v.41 no.4 s.115
• /
• pp.391-403
• /
• 2006

The Hanon volcano located in the southern pan of Cheju Island, Korea has a wetland in its crater being used as a farmland. Previous researchers presumed this wetland was a maar lake in the past. Based on the seismic refraction method, the wetland sediment layer was estimated between 5 to 14 m deep, which is mostly in accordance with previous researches. However, this shows only the depths at some sites, not representing the whole spatial distribution. This study is an attempt to reconstruct the volcanic lake in Hanon crater by applying the spatial statistical techniques based on the depth information from the seismic survey and known data. The procedure of reconstruction is as follows: First, the depth information from the seismic survey and known data were collected and it was interpolated by IDW and Ordinary Kriging method. Next, with the interpolation map and the present DEM the paleo DEM was constructed. Finally, using the paleo lake level on core data, the boundary of volcanic lake was extracted from the paleo DEM. The reconstructed lake resembles a half-moon in the north of the central scoria cone. It is estimated that the lake was 5 m deep on average and 13 m deep at the deepest point. Although there are slight differences according to the interpolation techniques, it is calculated that the area of the lake was between 184,000 and $190000m^2,$ and its volume approximately $869,760m^3$. Because of the continuous deposition processes after the crater formation, the reconstructed volcanic lake would not indicate an actual lake at a specific time. Nevertheless, it offers a significant clue regarding the inner morphology and evolution of the crater.

• Korean Journal of Plant Resources
• /
• v.14 no.1
• /
• pp.71-76
• /
• 2001

This experiment was conducted to investigate the effect of the mechanized and intergrated working system on the reduction of time and expenditure for job's tears (Coix lachryma-jobi L.) cultivation. Emergence rate of working system was 50% at the merchanized and 62% at the conventional. Total working time was 230 minutes/10a at the merchanized and 2,273 minutes/10a at the conventional. Expenditure was 111,061 won/10a at the merchanized and 189,781 won/10a at the conventional. Date of emergence, budding, and flowering were the same for two systems. Growth characteristics were similiar in two systems, corn borer rate was 3.0% at the merchanized and 13.3% at the conventional. Grain yield components was higher at the merchanized than at the conventional. Thereby, grain yield was 351 kg/10a at the merchanized and 309 kg/10a at the conventional.

• Journal of computational fluids engineering
• /
• v.19 no.4
• /
• pp.45-51
• /
• 2014

We develop a numerical method for solving the radiation hydrodynamic equations in one-dimensional spherical coordinates. The present method is validated through simulations of shock tube, thermal radiative diffusion and point explosion problems. The transient growth of the fireball is investigated by varying explosion yields. The present study clearly captures well-known breakaway phenomena related to the shock separation between pressure waves and thermal shock front. The fireball radius at the breakaway point is roughly increased by the yield to power of 0.4.

• Journal of the Speleological Society of Korea
• /
• v.44 no.45
• /
• pp.41-48
• /
• 1996

한라산을 중심한 제주도에는 수많은 용암류가 흘러 제주도를 형성하고 있다. 한라산 정상 화구에서 혹은 수많은 기생화산 화구에서 용암이 흘러 내려 이 용암지역에 수많은 용암동굴이 형성되고 있다. 세계에는 용암동굴이 1,000개소가 있고 그 중 50%가 미국의 서부에, 이탈리아에 186개, 후지산에 100개, 제주도에는 70개 정도가 알려지고 있다. 제주도 동,서 사면에는 광대한 용암대지가 있다. 점성이 작고 유동성이 강한 표선 현무암층이 분포한 관계로 세계적인 용암동굴 지대를 형성하고 있다.(중략)

• Proceedings of the Speleological Society Conference
• /
• 1997.10a
• /
• pp.60-67
• /
• 1997

한라산을 중심한 제주도에는 수많은 용암류가 흘러 제주도를 형성하고 있다. 한라산 정상 화구에서 흑은 수많은 기생화산 화구에서 용암이 흘러 내려 이 용암지역에 수많은 용암동굴이 형성되고 있다. 세계에는 용암동굴이 1,000개소가 있고 그 중 50%가 미국의 서부에, 이탈리아에 186개, 후지산에 100개, 제주도에는 70개 정도가 알려지고 있다. 제주도 동, 서 사면에는 장대한 용암대지가 있다. 점성이 작고 유동성이 강한 표선 현무암층이 분포한 관계로 세계적인 용암동굴 지대를 형성하고 있다.(중략)

• Nuclear industry
• /
• v.7 no.11 s.57
• /
• pp.84.1-85
• /
• 1987

• The Magazine of the IEIE
• /
• v.7 no.2
• /
• pp.8-12
• /
• 1980

• Proceedings of the KGS Conference
• /
• 2001.05a
• /
• pp.126-128
• /
• 2001

• The Journal of the Petrological Society of Korea
• /
• v.25 no.3
• /
• pp.283-298
• /
• 2016

Sangumburi crater, designated as Natural Monument No. 63, recognized as a maar, but precise geological mapping and geological characteristics in the field indicate that Sangumburi crater is a pit crater. Two stages of volcanic activities created Sangumburi pit crater. Lava flow (aphanitic pyroxene basalt I) and associated pyroclastic deposit (pyroclast I), composed of ash and lapilli, were formed at the stage 1. In the stage 2, lava flow (feldspar olivine basalt) was overlain by lava flow (aphanitic pyroxene basalt II) and associated pyroclastic deposit (pyroclast II), composed of agglomerate. Sangumburi pit crater formed at $0.073{\pm}0.036Ma$, determined by Ar-Ar age dating for the feldspar olivine basalt at the stage 2. It is not clear the preferred migration direction of subsurface magma after Sangumburi pit crater formed.