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電子ジャーナル
Cover image of 九州大学大学院理学研究院研究報告. 地球惑星科学
出版情報: [S.l.]. 九州大学大学院理学研究院
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2.
雑誌論文
Kyushu Univ. Production 九州大学成果文献
Cover image of 阿蘇中岳火山の二酸化硫黄および二酸化炭素ガス放出量の測定 — Observation of SO_2 and CO_2 fluxes in and around the active crater of Aso Nakadake Volcano
齋藤, 政城; Saito, Masaki; 松島, 健 ... [ほか]
出版情報: 九州大学大学院理学研究院研究報告. 地球惑星科学. 22, (2), pp. 51-62, 2007-02-15. 九州大学大学院理学研究院
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概要: Volatiles of the magma such as H2O, CO2, SO2, H2S and HCl, which are the main components of volcanic explosions, discharge to the surface of the earth as volcanic gases, hot springs, and river waters. The discharge occurs not only in volcanic eruptions but also in non-erupting activities. In order to clarify the mass balance of volatiles, the hydrothermal structure and the volcanic activities, it is very important to characterize the chemical constituents and the amount of the volatiles discharged from volcanoes. It is thought that the volcanic gases reflect immediately the changes of magmatic activity because the mobility of gases is the most abundant among the discharge forms of volatiles. The diffuse degassing from soil is one of the discharge forms paid attention in recent years. As CO2 is hardly influenced by the groundwater due to low solubility in water, the direct information on volcanic activities can be obtained by observing the CO2 flux and its changes. Aso volcano is one of the most active volcanoes in Japan, and magmatic eruptions have occurred several times in historical times. However, the research on the amount of the CO2 flux from the soil in and around the active craters had not been performed at Aso volcano. In this study, we estimated the CO2fluxes from the Nakadake crater and the circumference soil at Aso volcano and compared the results with the CO2fluxes at Kusatsu-Shirane volcano. At Aso volcano, the amount of the total CO2flux from soil was estimated to be about 0.12 ton d-1. While the amount of CO2flux from the Nakadake First crater was estimated to be 59+-95 ton d-1, and thus the CO2 flux from the crater was much larger than that from the soil at Aso volcano. On the contrary, the CO2 flux from the soil was comparable to that from the craters (fumaroles) at Kusatsu-Shirane volcano. 続きを見る
3.
雑誌論文
Kyushu Univ. Production 九州大学成果文献
Cover image of 大気化学における鉱物ダストの役割 — A review of the roles of mineral dust in atmospheric chemical reactions
鈴木, 一成; 長嶺, 篤; 赤木, 右 ... [ほか]
出版情報: 九州大学大学院理学研究院研究報告. 地球惑星科学. 22, (3), pp. 1-8, 2009-03. 九州大学大学院理学研究院
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概要: A considerable amount of mineral dust is circulating in the atmosphere. The chemistry of mineral dust plays an important role in not only the transformation of the material in the atmosphere but also in its climatic influence. In this paper, the mineral dust is first described in terms of chemistry and then the recent advances in the study of chemical reactions involving mineral dusts in the atmosphere are reviewed. Carbonate dust is the most reactive and vulnerable to chemical attack. Carbonates provide the acidic pollution with neutralizing agents, and SO2 with sites for oxidation reactions. Their surfaces become deliquescent with the absorption of nitrate. The step wise processes are displayed to show how other species are involved in the reactions. The reactions where by iron becomes more soluble are also reviewed. They are also important ones with respect to the climatic implication of dust. 続きを見る
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雑誌論文
Kyushu Univ. Production 九州大学成果文献
Cover image of 雲仙火山1991年6月3日の火砕流による人的被害 — Casualties by the 3 June 1991 pyroclastic flow at Unzen volcano
杉本, 伸一; 長井, 大輔; Sugimoto, Shinichi ... [ほか]
出版情報: 九州大学大学院理学研究院研究報告. 地球惑星科学. 22, (3), pp. 9-22, 2009-03. 九州大学大学院理学研究院
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概要: The 1990-1995 eruption of Unzen volcano, Japan, was characterized by lava dome growth and pyroclastic flows triggered by dome collapse. One of the largest pyroclastic flows occurred at 4:08 p.m. on June 3, 1991. The associated pyroclastic surge killed 43 people and injured 9 persons. The event was the worst volcanic disaster within a few decades in Japan. The victims due to the pyroclastic surge included following persons: fire brigade members watching for lahars and for safety of houses in the evacuation area, local residents returning home for retrieving their property and goods, press people taking photos of the pyroclastic flow, taxi drivers hired by the press, volcanologists recording volcanic activity on video tape, and policemen [OR a policeman] calling for peoples evacuation. Only a few people who were located near the distal end of the pyroclastic surge could survive. The mortality rate was 100% at the upstream area about 4.3 km from the source. The mortality extended to 69% at the downstream area near the distal end of pyroclastic surge. The overall survival rate (18%) is very low. This fact indicates that the only way to avoid disasters due to pyroclastic flows is to evacuate before they occur. Governments must designate the warned area and/or declare an evacuation instruction for residents to keep people out unconditionally, in cooperation with the volcanologists. 続きを見る
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雑誌論文
Kyushu Univ. Production 九州大学成果文献
Cover image of 島原半島地域における微動H/Vスペクトル比を用いた地盤構造推定 — Estimation of subsurface structure in the Shimabara Peninsula using microtremor H/V spectral ratio
糸谷, 夏実; 松島, 健; Itoya, Natsumi ... [ほか]
出版情報: 九州大学大学院理学研究院研究報告. 地球惑星科学. 23, (1), pp. 1-12, 2012-02-28. 九州大学大学院理学研究院 — Faculty of Sciences, Kyushu University
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概要: In recent times, the estimation of long-period strong ground motions has become more important in the construction of large-scale buildings. From the contour map of peak period for long-period ground motions in Japan (the Central Disaster Prevention Council, 2008), it has been estimated that long-period ground motions are amplified not only in sedimentary basins like the Kanto Plain in the central Japan, but also in volcanic areas such as the Shimabara Peninsula in Kyushu, Japan. In particular, in the Yadake region of the Shimabara Peninsula, the long-period ground motions are amplified to the same extent as in the Kanto Plain. In order to estimate the ground structure in the Shimabara Peninsula using microtremor H/V spectra (horizontal-to-vertical spectral ratio), we carried out microtremor observations at 60 sites throughout the Shimabara Peninsula. Using data derived from these observation sites, we traced a contour map of primary natural peak period (the longest peak period that ranges from 1 to 10 s). Peak periods of 5–6 s in the H/V spectra were observed at many of the observation sites to the east of the Shimabara Peninsula, where thick volcanic sediments are distributed. It is thought that the thick volcanic sediment layer is the cause of such long peak periods in the H/V spectra. In the central western area of the Shimabara Peninsula, there are no remarkable peaks in the observed H/V spectra. According to explosion seismic research (Explosion seismic research group of Unzen Volcano, 1995), this area corresponds to a rock layer having Vp = 3.5 km/s; this is a solid lava layer that extends to the ground surface. This structure is reflected in the shape of the H/V spectra; in this region, the value of H/V spectral ratio remains nearly constant in the frequency of microtremors. We also estimated subsurface structures in the peninsula using the observed H/V spectra. Using P-wave velocity obtained from the explosion seismic research, S-wave velocity and density were calculated according to Ludwig et al. (1970). Using a trial-and-error estimation process, S-wave velocity, P-wave velocity, and density were fixed, and the thickness of the sedimentary layers was adjusted to find a reasonable fit between the primary natural peak period of the calculated H/V spectra and the observed H/V spectra in order to determine the ground structure. The depth to the Vs = 600 m/s layer is estimated as 1.2 km at boring Site USDP2 which lies to the east of the Shimabara Peninsula. Our result is consistent with borehole sample data. The horizontal component of long-period microtremors in the Yadake area commonly exceeds that in the central part of the Shimabara Peninsula. If the ground structure is determined using the same parameters as the surrounding sites, the depth to the basement at Site Yadake should be approximately 1000 m. However, local tectonic maps and the results of explosion seismic research do not indicate such a steep basin structure under Site Yadake. Therefore, we varied the S-wave velocity of the shallow part of the underground structure and found that a very low-velocity layer exists beneath the area surrounding Site Yadake. It is thought that this low-velocity layer is related to the existence of numerous hot-spring sources in and around Site Yadake and causes an increase in long-period strong ground motions. 続きを見る
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雑誌論文
Kyushu Univ. Production 九州大学成果文献
Cover image of 西南日本,長崎県対馬に分布する新第三系対州層群からのメタン湧水性石灰岩の発見とその意義 — Seep limestone and chemosynthetic fossil assemblages dependent on the seep from the Neogene Taishu Group, Tsushima Island, Nagasaki Prefecture, the southwest Japan
二宮, 崇 ; Ninomiya, Takashi
出版情報: 九州大学大学院理学研究院研究報告. 地球惑星科学. 23, (1), pp. 13-21, 2012-02-28. 九州大学大学院理学研究院
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概要: Bivalve limestone and non bivalve limestone, occurs in the lower part of the Middle Formation of the Neogene Taishu Group, Tsushima Island, Nagasaki Prefecture, southwest Japan. The fossil fauna of the limestone and surroundings of the limestone are considered to be composed of chemosynthetic fossil ecosystem. This limestone is autochthonous originated from a methane seep, based on the occurrence, their very low carbon isotope ratios (δ13C; per mil PDB, respectively) and sulfur isotope ratios (δ34S; per mil PDB, respectively) of sulfide sulfur contained the limestone, and it is highly possible that the chemosynthetic ecosystem was maintained by hydrogen sulfide occurred anaerobic methane oxidation and/or originated from magma. The limestone indicates the existence of a large methane supply, possibly from methane hydrate. The fossil flora and molluscan fauna indicate the Taishu Group was deposited in a warm-temperate zone (mid-latitude), warmer than the climate of the present-day Tsushima district. The lower part of the Middle Formation was deposited in a deep-sea environment at water depths greater than 500 m, as indicated by the habitat depth of the molluscan fauna, the absence of photosynthesizing faunas, and the stabile condition of methane in mid-latitude regions. Rapid subsidence is considered to have occurred over a wide area during the maximum opening stage of the Japan Sea in the middle Miocene. However, in previous studies information concerning the middle Miocene strata indicating such deep-sea environmental conditions in the southwestern part of the Japan Sea is meager. The present findings from the Taishu Group such as limestone originated from a methane seep and of a fossil chemosynthetic ecosystem indicate the existence of a deep-sea environment over a wide area in the Japan Sea during the middle Miocene. These results suggest the early stage of the opening Japan Sea formed in a very deep and narrow ocean. 続きを見る
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雑誌論文
Kyushu Univ. Production 九州大学成果文献
Cover image of 中竜鉱山における3成分地震計アレイ観測 — Three component seismic array observation at galleries in Nakatatsu mine, Fukui, Japan
松本, 聡; Matsumoto, Satoshi; 松島, 健 ... [ほか]
出版情報: 九州大学大学院理学研究院研究報告. 地球惑星科学. 22, (4), pp. 1-8, 2011-03. 九州大学大学院理学研究院
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概要: We carried out seismic array observation in mining tunnels of Nakatatsu mine, Fukui, Japan. This observation site is located at about 20 kilometers away from the earthquake fault of Nobi earthquake (1891, M8.0). The major purposes in this observation are: 1) detection of small-scale heterogeneity around the fault; and 2) development of technique to explore structure by using seismic array data. Eighty seismometers which have three components with natural frequency of two hertz were deployed. The observation continued from September 2009 until the middle of February 2010. The sensors were connected to the recording system by cables. The data were converted to digital data by 24bit delta-sigma converter with maximum sampling interval of 1 ms and extracted from memory to storage by self-triggering algorithm in the system. The recording time is 16 – 64 sec. More than 100 earthquakes were recorded in the observation. We were able to obtain seismograms of not only local earthquakes but also distant earthquakes. The good environment for observation with hard rock site and low artificial noise allowed us to obtain high quality data. Some records of the earthquakes have adequate S/N ratios up to hertz. In addition, many scattered phases which could be generated by small-scale heterogeneity in the mid- to lower crust in this area were observed with sufficiently large amplitude. 続きを見る
8.
雑誌論文
Kyushu Univ. Production 九州大学成果文献
Cover image of 福岡市西区・九州大学伊都キャンパス地区の岩脈年代と地下水の化学組成 — K-Ar age determination of a lamprophyre dike, and geochemical features of groundwater in the Ito Campus, Kyushu University, Fukuoka
石橋, 純一郎; Ishibashi, Jun-ichiro; 小川, 啓太 ... [ほか]
出版情報: 九州大学大学院理学研究院研究報告. 地球惑星科学. 22, (2), pp. 63-74, 2007-02-15. 九州大学大学院理学研究院
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概要: Within the Ito Campus and surrounding area, subsurface investigations with several borings had been conducted by the Kyushu University. Core samples obtained by the boring and groundwater samples collected from the boring wells provide important information on understanding geological and geochemical features of this area. Age determination of a lamprophyre dike in the Itoshima Granitoid using K-Ar technique provided age of around 90.7±1.2 Ma, which is in accordance with the reported age for main body of the granitoid. This result would be one of constraints for discussion on igneous activities in the northern Kyushu. The groundwater collected from this area can be classified into four types based on the chemical and isotopic compositions. The relationship between water chemistry and water elevation can be explained as a snap shot of groundwater evolution from meteoric water to the Ca-HCO3 type groundwater accompanying weathering of granitic rocks. Within the alluvial sediments in the east of the Ito Campus, the Na-Cl type groundwater is widely distributed, which is attributed to the influence of seawater intrusion. The natural flow which is associated with the West Off Fukuoka Earthquake on March 20, 2005 is explained as a result of rising of the freshwater-seawater boundary. 続きを見る
9.
雑誌
Cover image of 九州大学大学院理学研究院研究報告. 地球惑星科学
九州大学大学院理学研究院 [編集]
出版情報: 福岡, Japan. 2000-2009. 冊 九州大学大学院理学研究院
巻次(年次): 21巻1号 (平12.12)-22巻3号 (平21.3)
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