著者

名和 一成 杉原 光彦 村田 泰章 風間 卓仁 西田 究 菅野 貴之 小山 悦郎 大久保 修平 奥田 隆

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.54, no.2, pp.59-67, 2008 (Released:2013-02-25)

参考文献数

17

被引用文献数

1

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We carried out continuous gravity observation with a Scintrex CG-3M gravimeter at Asama Volcano Observatory from September 4 to October 22 in 2007.We tried to detect hydrological gravity effects after heavy rainfall by Typhoon 200709 (FITOW). To detect hydrological gravity effects we supposed a simple tank model as proposed for the Matsushiro superconducting gravimeter observation, which model represented immediate gravity increase and gradual decrease after rainfall. Parameters of the tank model were estimated using an ABIC minimization iversion method and precipitation data as inputs. As a result, hydrological gravity effects were extracted from gravity residuals although gravity residuals included a large non-linear drift. And the extracted hydrological gravity effects corresponded to temporal gravity changes simultaneously observed with an FG5 absolute gravimeter. Our success promises expanding opportunities of continuous observation by using CG-3M gravimeters in the future.

著者

木股 文昭 石原 和弘 植木 貞人 内田 和也 小山 悦郎 佐藤 峰司 鈴木 敦生 高山 鐵朗 竹田 豊太郎 辻 浩 寺田 暁彦 中坊 真 浜ロ 博之 平野 舟一郎 松島 健 宮島 力雄 森 済 八木原 寛 山本 圭吾 渡辺 秀文

出版者

京都大学防災研究所

雑誌

京都大学防災研究所年報 (ISSN:0386412X)

巻号頁・発行日

vol.42, no.1, pp.35-43, 1999-04

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1998年以降, 火山活動が活発化している岩手山火山において, 火山活動に伴う地殻上下変動とその圧力源を議論する目的で, 水準路線を設置し, 1998年7, 9, 11月に精密水準測量を実施した。1998年9月3日, 水準測量実施中に, 直下でM6.1の地震が発生し, 20cmに達する断層運動を水準測量で検出した。岩手山南麓ではこの4ヶ, 月間に4cmに達する山側隆起の上下変動が観測され, その圧力源は岩手山西方に深さ3km前後と推定される。Earthquake swarm is observed around the Iwate-san Volcano, Northeast Japan since 1998. The leveling route with distance of 36 km was set up around the volcano and the precise levelings have been repeated to discuss the crustal deformation four times in July, September, September and November in 1998. When the precise levelingis doing in September 3, 1998, earthquake of M6. 1 was occurred close to the volcano. One leveling team was making leveling in the epicenter area, Re-levelings were repeated since the next day of the earthquake, and coseisimic deformations of 20 cm are detected along the leveling route. However the precursor of the vertical movements is not recognized in the leveling data made just before the earthquake. Uplift of the Iwate-san Volcano is observed and which amounts to 4 cm in the period of July to November in 1998. The pressure sources of the vertical deformations are estimated to be under the west side of the volcano with depth of 3 kim, which is the almost the same location of the pressure estimated by GPS measurements and the DInSAR (Differential Interferometric SAR).

著者

鈴木 由希 古川 晃子 中田 節也 藤井 敏嗣 渡邉 篤志 小山 悦郎

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.2008, 2008-10-10

著者

下鶴 大輔 行田 紀也 鍵山 恒臣 小山 悦郎 萩原 道徳 辻 浩

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.57, no.3, pp.p537-559, 1982

被引用文献数

3

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The Asama Volcano in central Honshu, Japan, suddenly erupted from the summit crater on 26 April, 1982. Since the last eruptive activity in 1973, the volcano had been apparently inactive in its surface manifestation. The first outbreak took place at 0225 hours followed by four minor eruptions, the last of which occurred at 0548 hours the same day. The staff members on night duty at the volcano museum at the northern foot of Asama were awakened by the rattling of a window facing the volcano. Immediately upon opening the window they heard the detonation and witnessed an incandescent eruption column and a pyroclastic flow gushing from the summit. The sound of the first detonation was not strong and only heard by a limited number of local residents.

著者

井田 喜明 長田 昇 沢田 宗久 小山 悦郎 鍵山 恒臣

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.64, no.2, pp.p325-345, 1989-09

被引用文献数

5

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火山噴火予知計画の一環として,地震研究所では,草津白根山の湯釜,涸釜,水釜火口の周囲に,6観測点からなる常設的な火山観測網を展開した.観測の中心は地震動であるが,地中温度,噴気温度,電気伝導度についても,連続観測を試行している.観測データは,無線テレメータにより,東京の地震研究所まで常時伝送される.地震研究所で受信したデータは,富士山や伊豆大島のデータと一緒に,ミニコンピュータにより,リアル・タイムで処理される.地震動のデータは,先ず振巾のレベルにより,次にノイズレベルや着震時刻も考慮して,地震かどうかの判定がなされる.更に,周辺の広域徴小地震観測網のデータと比較して,火山内部の地震かどうかが判断される.震源はオフラインで計算され,データに最もフィットするP波速度として2.5km/sが得られた.草津白根山では,1988年9月末から10月にかけて,火山性地震がやや群発的に発生した.その震源は,水釜火口南東部に集中した.その後,地震の震源は浅くなり,ほぼ同じ地点で間欠的な火山性微動が活発化した.1989年1月6日になると,連続的な微動が湯釜火口付近で起こり,24時間近くも継続した.それに伴って,湯釜火口の北西火口壁の付近の湖面下で,熱水か水蒸気(又は水蒸気を主体とする火山ガス)の急激な噴出があり,若干の火山灰が火口湖面およびその近傍に散布された.この小噴火の後には,震源が水釜火口南東部に集中する傾向は弱まった.水釜火口の南東部における火山性地震と火山性微動の活動は,マグマや水蒸気の移動と対応し,1月6日の小噴火の準備過程であったと推定される.A permanent network system for observations of volcanic activities have been installed in the vicinity of the Yugama, Karegama and Mizugama craters of Kusatsu-Shirane volcano. The system provides seismological data as well as preliminary results of continuous observations of underground temperatures, fumarolic temperatures and underground electric conductivities. All the data are continuously transmitted to the Earthquake Research Institute by a radio-wave telemetering system. The data are subject to real time processing in a mini-computer along with data of Fuji and Izu-Oshima volcanoes. Seismic events are first picked up, based on the amplitude level of the ground motions, and then examined in more detail, taking into account the noise levels, the arrival times and whether it occurred inside or outside the volcanic area. In the calculation of hypocenters, a P-wave seismic velocity of 2.5 km/s, which is best fit to the arrival times of the seismic waves, is assumed. Swarm-like seismic activity was observed from the end of September through October, 1988 at Kusatsu-Shirane volcano. Most of the determined hypocenters during this activity were concentrated below a specific point southeast of the Mizugama crater. In the following period, hypocenters were shifted to the shallower part of the same area, and the episodic volcanic tremors were more frequent. On January 6, 1989, a continuous volcanic tremor suddenly occurred and lasted for almost 24 hours. This tremor was accompanied by a silent extrusion of hot steam or water at the northwest part of Yugama crater with a small amount of volcanic ash distributed over the Yugama crater lake. After this small eruptive event, the hypocenters of volcanic earthquakes became more scattered. It is inferred that the volcanic earthquakes and tremors centered southeast of the Mizugama crater reflect the underground migration of magma or hot steam, and were precursors of the eruptive event on January 6.