著者

海野 徳仁 長谷川 昭 小原 一成 松沢 暢 清水 洋 高木 章雄 田中 和夫 小菅 正裕

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.38, no.3, pp.399-410, 1985-09-25 (Released:2010-03-11)

参考文献数

13

被引用文献数

1 6

---

Hypocenter determination for aftershocks of the 1983 Japan Sea Earthquake (M7.7) is made by using the seismic networks of Tohoku University and of Hirosaki University. The obtained aftershock area is 160km long in north-south direction with a width of 40km, distributing itself along the eastern margin of the Japan Basin. Most of the aftershocks are located within the area bordered by the 2000m and 3000m isobaths, northern and southern ends being surrounded by the Sado Ridge and the Oshima Plateau, respectively. Precise hypocenter distribution deliniates an eastward dipping fault plane with a shallow dip angle. Almost all the aftershocks are located in the crust, which is consistent with the fact that the PMP phase is clearly observed from most of the aftershocks.A remarkable later phase is observed at many stations 4-7 sec after the P arrival. This later phase is interpreted as the reflected wave both at the sea surface and at the Moho discontinuity (pwPMP). Focal depth distribution estimated from arrival time differences between PMP and pwPMP phases also shows the eastward dipping fault plane with a shallow dip angle.Foreshock activity started 12 days before the occurrence of the main shock within a concentrated area in the vicinity of the main shock hypocenter. All the foreshocks are classified into two groups: one with high peak-frequency and the other with low peak-frequency, each having very similar wave forms. Hypocenters of low peak-frequency events are located at shallower depths than those of the main shock and high peak-frequency events.

著者

浜口 博之 長谷川 昭 植木 貞人 高木 章雄

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.97, no.4, pp.333-340, 1988-08-25 (Released:2011-02-17)

参考文献数

15

著者

長谷川 昭 堀内 茂木 植木 貞人 西澤 あずさ 松澤 暢 海野 徳仁 堀 修一郎 稲盛 隆穂 松本 聡 浜口 博之 高木 章雄 田中 和夫 鈴木 将之 末広 潔

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.42, no.2, pp.161-169, 1989-06-24 (Released:2010-03-11)

参考文献数

17

被引用文献数

1 1

---

A seismic refraction experment was carried out around the Bandai volcanic area, the southern part of the Tohoku District, by using a large capacity (9 liter air chamber) marine airgun. Shallow crustal structure (down to about a 4km depth) obtained along the 30km-length profile shows the swelling of the second layer with P-wave velocity more than about 4.0km/s just beneath Bandai volcano in parallel to the surface topography. The swelling of the second layer by about 1km is in good agreement with that of the basement estimated from the Bouguer anomaly.Seismic signals from the surrounding telemetered stations of Tohoku University at epicentral distances from 10km to 230km, are continuously recorded during the airgun experiments. In the stacked records we can detect the clear first P arrivals from the airgun shots at the stations with distances ranging up to 150km, which shows the usefullness of the marine airgun for studying the crustal structure on land. Anomalously late P arrivals or unclear P arrivals are observed for the ray paths which cross active volcanoes. This result and the shallow crustal structure obtained along the refraction profile suggest the existence of the anomalous zone beneath Bandai volcano at depths deeper than about 4km.

著者

長谷川 昭 海野 徳仁 高木 章雄 鈴木 貞臣 本谷 義信 亀谷 悟 田中 和夫 澤田 義博

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.36, no.2, pp.129-150, 1983-06-25 (Released:2010-03-11)

参考文献数

18

被引用文献数

13 13

---

Precise relocation of earthquakes occurring in Hokkaido and northern Honshu during the period from January, 1979 to October 1981 is made by using 35 stations of the microearthquake observation networks of Tohoku University, of Hokkaido University, of Hirosaki University and of Central Research Institute of Electric Power Industry. Obtained hypocenter distribution shows the double-planed structure of the deep seismic zone in the whole area of Hokkaido and northern Honshu including the junction between the northeastern Japan arc and the Kurile arc. At the junction the deep seismic zone is contorted but is still double-planed at least in the upper 150km depth range. Beneath the southern end of the Kurile arc (central and eastern Hokkaido) the upper seismic plane of the double seismic zone disappears at depths greater than about 120km, whereas the seismicity in the upper seismic plane is still active in this depth range beneath the northeastern Japan arc.Hypocenters on the deep seismic zone beneath Hokkaido, relocated in the present study, are systematically shifted to the SE or SSE direction in comparison with the locations by the Hokkaido University network. This systematic shift of hypocenters is found to be well explained by the existence of the subducted lithosphere with seismic wave velocities higher than the surrounding mantle.

著者

伊藤 綾 竹内 浩二 高木 章雄 櫻井 文隆 渋澤 英城 菅谷 悦子 栄森 弘己 山岸 明

出版者

関東東山病害虫研究会

雑誌

関東東山病害虫研究会報 (ISSN:13471899)

巻号頁・発行日

vol.2006, no.53, pp.153-156, 2006-12-01 (Released:2010-03-12)

参考文献数

6

---

近年, 東京都の江東地域においてエダマメの葉の黄化や生育不良, 収穫減少などの生育障害が発生している。そこで2005年に都内のエダマメ圃場63カ所を調査した結果, 江東地域では20圃場で生育障害が発生していた。そのうち19圃場では根部にダイズシストセンチュウのシストの寄生と, 土壌中に高密度の本種のシストと卵を認め, ダイズシストセンチュウが生育障害の原因となっている可能性が高いと考えられた。なお, 多摩地域においても初めて本種の分布を確認した。

著者

堀内 茂木 山本 明 松沢 暢 河野 俊夫 長谷川 昭 高木 章雄 伊神 輝 山田 守 青木 治三

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.38, no.4, pp.529-539, 1985-12-25 (Released:2010-03-11)

参考文献数

11

被引用文献数

1

---

A real-time system of automatic detection and location of seismic events has been developed by using a personal computer. Since speed of computation by a personal computer is low, a simple digital band-pass filter has been developed for the real-time system. The band-pass filter needs only several times of addition and subtraction to get an output. Event dection is based on a ratio of short to long term average of outputs of the filter whose cutoff frequencies are set to decrease amplitude of long period noise owing to microtremor and amplitude of short period noise owing to culture. Arrival times of the P and S waves are determined by applying Akaike Information Criterion (AIC) to outputs of the band-pass filter with narrow band whose central frequency is set to be a value of predominant frequency of the seismic signal.A temporary seismic observation with 8 stations for the aftershocks of the 1984 Western Nagano Prefecture Earthquake has been made by the use of radio and telephone telemetries. The real-time system of the automatic location of the seismic events was tested to demonstrate that hypocenter distribution obtained by the real-time system is nearly consistent with that determined from arrival time data which were read manually. It is shown that hypocenters of 60% among triggered events can be determined by this real-time system.