著者

山岡 耕春 中禮 正明 安藤 雅孝

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.111, no.2, pp.185-191, 2002-04-25 (Released:2009-11-12)

参考文献数

9

被引用文献数

2 2

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The temporal relationship between the interplate and inland earthquakes of Kyushu Island region was investigated. We analyzed this relationship by stacking the temporal frequency of the inland earthquakes with reference to the occurrence time of each major interplate earthquake in the Hyuga-nada region, that occurred between 1900 and 2000. A good coincidence of occurrence between the inland and the interplate earthquakes is recognized. While the tendency of the occurrence after the interplate events has already been pointed out, we found that the inland earthquakes also tend to occur before the interplate events. Abrupt activation of the inland earthquakes within several months before major interplate earthquakes is recognized in addition to the tendency to occurr afterwards. The preceding inland earthquakes may indicate that they are triggered by precursory slow slips around the hypocenters of the Hyuga-nada earthquakes.

著者

山岡 耕春

雑誌

日本地震学会ニュースレター : News letter (ISSN:09195319)

巻号頁・発行日

vol.23, no.3, pp.26-28, 2011-09-10

参考文献数

2

著者

山岡 耕春

出版者

公益財団法人 日本学術協力財団

雑誌

学術の動向 (ISSN:13423363)

巻号頁・発行日

vol.23, no.3, pp.3_88-3_90, 2018-03-01 (Released:2018-07-28)

参考文献数

2

被引用文献数

2

著者

井田 喜明 山岡 耕春 渡辺 秀文

出版者

特定非営利活動法人 日本火山学会

雑誌

火山.第2集

巻号頁・発行日

vol.33, pp.S307-S318, 1988

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Various features of the eruption that began on November 15, 1986 in Izu-oshima volcano are examined to infer the underground magmatic activities and the mechanism of the eruption. A massive dike intrustion that is assumed to have happened at the same time as the fissure eruption cannot explain the seismicity, deformation and other evidence consistently. Another preferable model that gives a systematic explanation of the available data is proposed as follows. A magma reservoir was situated at a depth of about 5 km below a NW (north-western) flank of Izu-Oshima volcano. This magma reservoir supplied magma to the summit crater through a well-developed vent, and caused the first summit eruption under an enhanced NW-SE compressive component of the tectonic stress. As the magma reservoir deflated with the discharge of magma in this summit eruption, a compressive stress increased in the neighboring area centered at the northern rim of the caldera. The stress finally fractured this area with intense seismicity, and produced fissures. Along these fissures, the magma that had penetrated into interstital space between rocks effused explosively with bubbling of steam. The magma had been more or less cooled and chemically differentiated in the interstitial space so that the ejecta from this fissure eruption was more felsic. The deflation of the magma reservoir due to the summit and fissure eruption resulted in a significant subsidence of the NE part of the island. Strain associated with opening of the volcanic fissures was transmitted through a strike-slip fault to the SE part of the island, and caused a local extensional stress and graben there.

著者

井田 喜明 山岡 耕春 渡辺 秀文

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.63, no.2, pp.183-200, 1988-11-11

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伊豆大島火山の山頂火口で,1986年12月以後に発生した3回の小噴火について,その発生機構を考察し,以下のモデルを提案する.伊豆大島火山の北西山腹の地下には,約5kmの深さにマグマだまりが存在する.1986年11月の山頂噴火と割れ目噴火では,マグマだまりの圧力が高まり,そこからマグマが上昇した.その後伊豆大島火山ではマグマの後退が進行し,そのような状況下で,12月以後の小噴火が発生した.マグマの後退は,火道内に空洞をつくり,同時にマグマの圧力を低下させて,水蒸気の発泡を促進する.1987年11月16日の噴火前には,長い前駆期間を通じて,水蒸気の発泡,移動と,火道上部におけるその蓄積が進行した.水蒸気の発生,上昇過程は,火山性微動を生み,空洞に蓄積された水蒸気の高まりは,地震と噴気の活動を活発化した.十分に高まった水蒸気圧は,最終的には,噴火と対応する爆発を起こすに至った.一方,1986年12月18日と1987年11月18日の噴火では,マグマの後退のために生じた火道内の空洞が,重力不安定で崩壊した.旧火口内部にたまっていたマグマは,3回の小噴火で段階的に地下に逆流した.逆流は,1987年11月18日の噴火のときが最も顕著で,その効果は,火道を伝わってマグマだまりの圧力を急激に高め,伊豆大島内外の傾斜や体積歪に,系統的な変化をもたらした.

著者

山岡 耕春

出版者

特定非営利活動法人日本火山学会

雑誌

火山 (ISSN:04534360)

巻号頁・発行日

vol.39, no.4, pp.141-153, 1994-09-20

被引用文献数

2 3

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Relations between activity of volcanic earthquakes in Izu-Oshima volcano and stress and/or strain state around it are investigated. In this paper three kinds of relations are examined during and after the 1986 eruption of Izu-Oshima volcano : (1) How did big earthquakes affect on the volcanic activity of Izu-Oshima? (2) How did the pressure decrease of magma reservoir induce earthquakes around it. (3) How did the dike intrusion induce big earthquakes. The results are as follows : (1) Nine earthquakes of M>5.0 occurred from 1987 through 1990 within the epicentral distance of 100 km from Izu-Oshima volcano. They gave influences on the activity of volcanic earthquakes and/or volcanic tremor when they exerted normal strain of over 10^<-8> on the vertical plane trending N30W. (2) Swarm-like seismic activity in north and western part of Izu-Oshima volcano during the summit eruption is interpreted as an induced swarm due to pressure decrease of magma reservoir. The earthquake swarms occurred both sides of the magma reservoir whose location is estimated from the data of crustal movement. The location of two-lobed earthquake swarm is well explained by a simple model ; infinite two-dimensional elastic medium under differential stress with a circular hole. (3) Large earthquakes accompanied the dike intrusion of 1986 eruption of Izu-Oshima. Two biggest earthquakes occurred at both ends of the dike. A M 5.1 event occurred at the northwestern end and M 6.0 occurred at the southeastern end. Both events may played a role to stop the further propagation of dike intrusion.

著者

山岡 耕春 中禮 正明 安藤 雅孝

出版者

公益社団法人 東京地学協会

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.111, no.2, pp.185-191, 2002-04-25

参考文献数

9

被引用文献数

2

---

The temporal relationship between the interplate and inland earthquakes of Kyushu Island region was investigated. We analyzed this relationship by stacking the temporal frequency of the inland earthquakes with reference to the occurrence time of each major interplate earthquake in the Hyuga-nada region, that occurred between 1900 and 2000. A good coincidence of occurrence between the inland and the interplate earthquakes is recognized. While the tendency of the occurrence after the interplate events has already been pointed out, we found that the inland earthquakes also tend to occur before the interplate events. Abrupt activation of the inland earthquakes within several months before major interplate earthquakes is recognized in addition to the tendency to occurr afterwards. The preceding inland earthquakes may indicate that they are triggered by precursory slow slips around the hypocenters of the Hyuga-nada earthquakes.

著者

山岡 耕春 井田 喜明 山科 健一郎 渡辺 秀文

出版者

特定非営利活動法人 日本火山学会

雑誌

火山.第2集 (ISSN:04534360)

巻号頁・発行日

vol.34, no.4, pp.263-274, 1989

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Mt. Mihara of Izu-Oshima Volcano exploded on November 16, 1987 after one year's rest of its eruptivity. The eruption followed an intensive activity of earthquakes at the summit which began in January 1987. We studied the earthquakes and their mechanisms with a closely installed seismograph network around the summit. We found that most of the earthquakes occurred very narrow portion just below the summit crater with radius of 300 m. Their focal depths are shallower than 100 m above sea level. Most of the focal mechanisms are of normal types. The seismic activity ceased after this event. These facts show that the earthquakes were caused by small break of the bottom of the crater which was filled with the lava of the 1986 eruption, probably due to the load of the lava. The event on November 16 was the final break of the bottom which supported the load of the lava above it. The explosion on November 16 was caused by the sudden fall of both the bottom and the lava above it. The pressurized gas in the cavity below the bottom moved explosively upward in exchange of the falling body.

著者

雑賀 敦 平松 良浩 大井田 徹 山岡 耕春

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.76, no.1, pp.75-86, 2001-07-25

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Spatial and temporal variations in seismic anisotropy in the crust are investigated using earthquakes in the crust and at the upper boundary of the subducting Philippine Sea plate in the Tokai region, central Japan. We use waveform data from December 1986 to August 1999 recorded by the micro-earthquake observation network of the Research Center for Seismology and Volcanology, Nagoya University. The method of Silver and Chan (1991) is applied to evaluate splitting parameters, a leading shear-wave polarized direction and a delay between two polarized waves. A total of 362 high-quality waveform data within the incident angle of 35° are analyzed in this study. The leading shear-wave polarized directions are approximately E-W, in spite of differences of focal depths. This direction is consistent with the direction of regional horizontal maximum compressive stress in the Tokai region reported before. The time delay increases in proportion to the focal depth. These results indicate that the regional compressive stress controls anisotropy not only in the upper crust but also in the lower crust. Assuming the uniform distribution of anisotropy, the degree of anisotropy is estimated to be 0.5% in the lower crust. An increase in time delays between two-polarized waves is found before and after the Aichi-ken Tobu earthquake (M = 5.7) in 1997 at the station STN. This variation is statistically significant with the confidence level of 99.999% and is not an apparent change due to a variation in hypocenter distribution. No temporal variation of splitting parameters is found at the station INU. These results can be explained by a change of the volumetric and areal strain in the most-upper part of the crust due to the postseismic slip of the Aichi-ken Tobu earthquake.

著者

山岡 耕春 Yamaoka Koshun

巻号頁・発行日

1986-03-25

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The buckling phenomena of the subducting lithosphere dueto the sphericity or the earth are studied by a nonlinearfinite element method, and the results are compared with thebuckling experiments by Yamaoka et a1. (1986b). Thesubduction or the lithosphere is modeled by a hemisphericalshell squeezed at its circumferential edge. For simplicity,two parameters are employed in scaling the subductinglithosphere. One is the thickness or the lithosphere andthe other is the length or its deformable portion (i.e. , thelength of the descending slab). Uniform inward load isapplied to the free circumferential edge or the deformableportion. At the opposite edge (i.e., at the trench),built-in boundary condition is imposed; no displacements andno rotations are allowed. Investigations are made mainly onthe following three subjects: (I) How do the two parameterscontrol the wavelength of buckling? The results show thatshorter waves are associated with thinner and shortershells. The irregularities such as tears or seamounts donot alter the buckling wavelength very much. (2) How doshells deform in their postbuckling state. Sharp cuspspointing outward appear in the postbuckling undulationwithout any irregularities in shell property and in appliedload・The shape or the cuspidal undulation is quite similart.o that of the actual subducting lithosphere. (3) Canbuckling take place in the subducting lithospbere underlikely conditions in the earth? The examination is madewith respect to the buckling load, the shell deflection, andthe buckling wavelength. The results strongly suggest thatthe arcuate shapes of subduction zones are in fact generatedby buckling or the subducting lithosphere.

著者

木股 文昭 山岡 耕春 藤井 直之

出版者

特定非営利活動法人 日本火山学会

雑誌

日本火山学会講演予稿集 (ISSN:24335320)

巻号頁・発行日

vol.1991, 1991

著者

前田 裕太 寺川 寿子 加藤 愛太郎 山中 佳子 古本 宗充 山岡 耕春 堀川 信一郎 松廣 健二郎 奥田 隆

出版者

特定非営利活動法人日本火山学会

雑誌

日本火山学会講演予稿集

巻号頁・発行日

vol.2014, 2014-11-02

著者

山岡 耕春

出版者

公益社団法人 精密工学会

雑誌

精密工学会誌 (ISSN:09120289)

巻号頁・発行日

vol.71, no.11, pp.1325-1329, 2005-11-05 (Released:2009-04-10)

参考文献数

3

著者

河村 将 工藤 健 山岡 耕春 古本 宗充

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.63, no.3, pp.123-137, 2011-02-25 (Released:2012-03-26)

参考文献数

16

被引用文献数

1

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We developed a comprehensive statistical validation system of crustal activities with which to easily address spatially and temporally sufficient range of a database of geophysical measures. The system involves carrying out the following four processes: (1) creating the database of geophysical measures with spatially and temporally gridded and other convenient formats, (2) comparing any two geophysical measures, at least one of which is time-variable, (3) classifying the spatiotemporal relationship of these geophysical measures into some types by defining a statistical index, and (4) evaluating and validating the relationships between classification results and the occurrence of target physical events such as large inland earthquakes. With the system, we aim for making a statistical model, or an appropriate rule for monitoring of crustal activities. Formulation of the rule is, in turn, expected to lead to comprehensive understanding of crustal activities. Here, we focused on the relations of seismicity and strain rate to introduce the conception and algorithm of the system. The system requires input of the database and other parameters and leads to output of various spatiotemporal distributions, 2-by-2 contingency tables, and probability gains for prediction and alarm rates for target physical events.

著者

雑賀 敦 平松 良浩 大井田 徹 山岡 耕春

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.76, no.1, pp.75-86, 2001-07-25

---

Spatial and temporal variations in seismic anisotropy in the crust are investigated using earthquakes in the crust and at the upper boundary of the subducting Philippine Sea plate in the Tokai region, central Japan. We use waveform data from December 1986 to August 1999 recorded by the micro-earthquake observation network of the Research Center for Seismology and Volcanology, Nagoya University. The method of Silver and Chan (1991) is applied to evaluate splitting parameters, a leading shear-wave polarized direction and a delay between two polarized waves. A total of 362 high-quality waveform data within the incident angle of 35° are analyzed in this study. The leading shear-wave polarized directions are approximately E-W, in spite of differences of focal depths. This direction is consistent with the direction of regional horizontal maximum compressive stress in the Tokai region reported before. The time delay increases in proportion to the focal depth. These results indicate that the regional compressive stress controls anisotropy not only in the upper crust but also in the lower crust. Assuming the uniform distribution of anisotropy, the degree of anisotropy is estimated to be 0.5% in the lower crust. An increase in time delays between two-polarized waves is found before and after the Aichi-ken Tobu earthquake (M = 5.7) in 1997 at the station STN. This variation is statistically significant with the confidence level of 99.999% and is not an apparent change due to a variation in hypocenter distribution. No temporal variation of splitting parameters is found at the station INU. These results can be explained by a change of the volumetric and areal strain in the most-upper part of the crust due to the postseismic slip of the Aichi-ken Tobu earthquake.

著者

及川 純 藤田 英輔 今西 祐一 山岡 耕春 井田 喜明

出版者

特定非営利活動法人日本火山学会

雑誌

日本火山学会講演予稿集

巻号頁・発行日

vol.1994, no.2, 1994-10-20

著者

山岡 耕春

出版者

国土計画協会

雑誌

人と国土21 (ISSN:13469576)

巻号頁・発行日

vol.39, no.3, pp.16-20, 2013-09

著者

山岡 耕春

出版者

日本航空宇宙学会

雑誌

宇宙科学技術連合講演会講演集 (ISSN:18841945)

巻号頁・発行日

vol.57, 2013-10-09

著者

山岡 耕春 Yamaoka Koshun

巻号頁・発行日

1986-03-25 (Released:2009-12-22)

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名古屋大学博士学位論文 学位の種類 : 理学博士(課程) 学位授与年月日 : 昭和61年3月25日

著者

鍵山 恒臣 筒井 智樹 三ヶ田 均 森田 裕一 松島 健 井口 正人 及川 純 山岡 耕春 熊谷 博之 西村 裕一 宮町 宏樹 渡辺 了 西村 太志 高木 朗充 山本 圭吾 浜口 博之 岡田 弘 前川 徳光 大島 弘光 植木 貞人 橋本 恵一 仁田 交一 茂原 諭 中道 治久 汐見 勝彦 中原 恒 青木 重樹 青地 秀雄 井田 喜明

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.70, no.2/4, pp.33-60, 1996-03-15

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In recent years, investigations on the structures of volcanoes have been noteworthy for further understanding volcanic processes, including locations of magma reservoirs, magma rising process before eruptions and causes of related phenomena. In 1994, a joint experiment was conducted on Kirishima Volcanoes, Southern Kyushu, to reveal the structure and the magma supply system by a group of scientists from national universities under the National Research Project for the Prediction of Volcanic Eruptions. The experiment was carried out by seismological, electromagnetic and other geophysical methods. The following seven papers including this one present some results of the experiments. This paper outlines a seismic explosion experiment in Kirishima, and presents all data on the first motion. An extensive explosion seismic experiment was conducted on December 1, 1994. Observations were made along a 30-km major line lying in the NNW-SSE direction and other sub-lines which cross the major line in and around the Kirishima Volcanoes. Along these lines, 6 shots with a charge size of 200-250 kg, and 163 temporary observations were arranged by many universities and institutes. A newly developed data logger was used for these temporal observations, and the position of each site was determined by GPS. All 6 shots were successfully fired, and clear onset and significant phases were observed at most observation sites. A travel time diagram suggests that a high velocity layer crops out south of the Kirishima Volcanoes, while in the Kirishima Volcanoes, this layer is covered with a lower velocity layer, which is thick at the northern part. It is also suggested that a structural discontinuity exists between S3 and S4.