| Project/Area Number |
05041062
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Field Research |
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| Research Institution | Kyoto University |
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Principal Investigator |
ANDO Masataka Disaster Prevention Research Insitute, Kyoto University, 防災研究所, 教授 (80027292)
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| Co-Investigator(Kenkyū-buntansha) |
BAUTISTA Bart Philippine Institute of Volcanology and Seismology, 地震研究部主任
PUNONGBAVAN レイムンド フィリピン火山地震研究所, 所長
OIKE Kazuo Faculty of Science, Kyoto University, 理学部, 教授 (40027248)
TATSUMI Yoshiyuki College of Liberal Arts and Sciences, Kyoto University, 総合人間学部, 助教授 (40171722)
NISHIGAMI Kinya Disaster Prevention Research Insitute, Kyoto University, 防災研究所, 助手 (00189276)
OHKURA Takahiro College of Liberal Arts and Sciences, Kyoto University, 総合人間学部, 助手 (40233077)
SHIBUTANI Takuo Disaster Prevention Research Insitute, Kyoto University, 防災研究所, 助手 (70187417)
PUNONGBAYAN Raymund Philippine Institute of Volcanology and Seismology
BART Bautist フィリピン火山地震研究所, 地震研究部, 主任
RAYMUND Puno フィリピン火山地震研究所, 所長
伊藤 潔 京都大学, 防災研究所, 助教授 (80022721)
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| Project Period (FY) |
1993 – 1994
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| Project Status |
Completed (Fiscal Year 1994)
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| Budget Amount *help |
¥10,000,000 (Direct Cost: ¥10,000,000)
Fiscal Year 1994: ¥5,000,000 (Direct Cost: ¥5,000,000)
Fiscal Year 1993: ¥5,000,000 (Direct Cost: ¥5,000,000)
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| Keywords | The Philippines / Taal volcano / Seismic exploration / Magma chamber / Regional stress field / Volcanic eruption / Artificial seismic source / Seismi arvay observation / 人工地震探査 / カルデラ / 反射面 / 溶融体 / レシーバー関数 / 地下構造 |
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| Research Abstract |
Taal Volcano is strato-volcano which is composed of a 15*22km^2north-south trending caldera lake and a volcanic island with extent of about 5*5km^2 centered in the lake and known as one of the most active volcanoes in Philippines, though no eruption has occured since 1977. We carried out seismic explosion surveys two times, for the first time in Philippines, at Taal Volcano. In March, 1993, two explosions were executed on the west shore of the caldera lake and seismic waves that passed beneath the volcano were recorded by 30 digital event recorders installed on the east shore along the fan-shooting survey line. Next, in February, 1994, one explosion was made on southeast shore and wave signals were recorded by 27 event recorders on the west to north shore. We noticed significant differences between the seismic waves that passed just below the main crater and those traveled outside of the crater. The former waves attenuate more strongly and propagate more slowly than the latter waves, a
… More
nd the former waves are followed by reflected phases with large amplitude which show faster apparent velocity than initial P arrivals. The P velocity structure is derived from the direct and refracted P waves that passed outside of the main crater by using the time-term method. The result is as follows ; the surface layr, 1.8 km/s with thickness of 0.1 to 1km, the second layr, 3.6km/s with thickness of 0.3 to 2km, and the third layr, 5.6km/s. The delay of P arrivals that passed beneath the main crater is 0.2 to 0.4sec, which cannot be explained in terms of the time-terms beneath the stations. These results show the existence of low-velocity and low-Q region at about 2 km depth and the region is located within the horizontal extent of 2*2km^2 and about 5 km east of the main crater by the two surveys. The result of normal-moveout-correction shows that the reflection phases mentioned above come from about 7 km depth and 5 km east of the main crater. This reflector may suggest the top surface of magma chamber, and in this case, the low-velocity and low-Q zone should be restricted only shallower part of the third layr because of large amplitude of the reflected phases. Less
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