著者

岸本 兆方 尾池 和夫 渡辺 邦彦 佃 為成 平野 憲雄 中尾 節郎

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.31, no.3, pp.265-274, 1978-10-31 (Released:2010-03-11)

参考文献数

8

被引用文献数

1

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Continuous observation of micro-earthquakes has been done by a network of the Tottori Micro-earthquake Observatory since 1964 and it has been done by a network of the Hokuriku Micro-earthquake Observatory since 1971. These networks were improved by setting up the telemeter observation system and by the development of recording system since 1976.Signals of three components of short period seismic waves observed at 8 satellite stations are transmitted continuously through the telephone lines to the Tottori Observatory. Signals observed at 7 satellite stations are transmitted to the Hokuriku Observatory. Only vertical components of selected three stations are transmitted from the Tottori and the Hokuriku Observatory to the Disaster Prevention Research Institute in Uji and continuously recorded by long term ink-writing recorders.These seismic waves are recorded by three kinds of recording systems at each observatory. Seismic activity is continuosly monitored by newly developed long term ink-writing recorders for vertical components of all stations. Earthquakes observed at more than two of key stations are recorded by data-recorder and pen-recorder with 14 channel recording units started by a triggering signal.Overall frequency range of the telemetering observation system is from 1 to 50Hz and dynamic range is about 40db. Maximum time delay of lines is about 20msec. This time delay is constant for each line and can be corrected for the accurate calculation.

著者

尾池 和夫 松村 一男

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.359-364, 1985-09-25 (Released:2010-03-11)

参考文献数

2

被引用文献数

2

---

A new system for the temporary observation of earthquakes have been developed. Analogue memories by CMOS-RAM and usual audio cassette stereophonic recorder are used for the system. They are well developed and cheap. Seismic wave signals and time code signals are holded in the memories by the trigger signal and recorded into a cassette as the audio signals converted by high frequency sampling clock. Multichannel observation is possible by the channel serial output.Playback of signals is done by the simple memory system converting signals from audio frequency to the suitable frequency. Audio signal analyzers are also available for the direct playback signals of the tape recorder.In the case of two-channels. recorder which wee call OM-2 type, , using WM-D6C recorder with Dolby-B noise reduction system, 46-db dynamic range can be gotten for each channel. We are observing microearthquakes at more than 20 temporary stations by the recorders with a high-gain and a low-gain channel for one component vertical senser to get records of microearthquakes and unsaturated records of largee shocks. About 900 eventss are stored in a 60 minutes cassette tape in this case.

著者

尾池 和夫

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.24, no.4, pp.318-334, 1972-01-31 (Released:2010-03-11)

参考文献数

16

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The distributions of stresses around an elliptical fault plane in an infinite homogeneous elastic medium have been calculated. There are some regions where shearing stresses are not decreased but significantly increased. It indicates that a shear fault has a strong tendency to propagate itself and this corresponds to the occurrence of aftershocks. From the change of each components of stresses it is expected that large aftershocks which occur on and around the x1 and x2-axis have similar mechanism to that of a main shock, and aftershocks in other regions have different mechanisms.Dynamic displacements in the near field around a propagating fault have been calculated for the various types of faulting. The different characteristics of the fault are reflected in the wave forms related to the far field terms. There are some regions where the polarities of initial dynamic displacements are opposite to those of static displacements. Some of the results given by HASKELL (1969) have been checked under the same conditions as his calculations and essentially different results have been obtained.

著者

宇佐美 竜夫

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.16, no.3, pp.145-148, 1963-09-30 (Released:2010-03-11)

参考文献数

2

---

The equation of equilibrium of a homogeneous and isotropic elastic medium is solved for the orthogonal curvilinear coordinates of two dimensions under the condition that Laplace's equation is separable. Coordinates systems satisfying these conditions are Cartesian, cylindrical, elliptic cylindrical and parabolic cylindrical ones.First, solutions of equation of motion is obtained. Then, making frequency in these solutions to zero, the equation of equilibrium is solved.

著者

宇佐美 龍夫

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.5, no.3, pp.71-76, 1952-09-30 (Released:2010-03-11)

参考文献数

2

---

The reflection and refraction of plane SH waves incident upon a high-speed layer with a constant thickness d were studied. Numerical calculations were executed in a case when B1/B2=0.5507, μ2/μ1=3.25, and medium 1 and 3 are equal, and the results are given graphically. According to the results, the so-called total reflection is considered to be taken place when d/L≥5, and no plane SH waves can be propagated parallel to the discontinuous layer.

著者

宇佐美 龍夫 濱松 音蔵 久本 壮一 渡邊 健 中村 亮一 植竹 富一

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.45, no.3, pp.339-351, 1992-12-24 (Released:2010-03-11)

参考文献数

27

---

For the study of macroscopic characteristics of earthquake, it is necessary to investigate both historical and modern earthquakes from the same point of view. Historical earthquakes present informations on damages only. Modern earthquakes have various kind of data obtained from instrumental observations. Intensity data is common to both old and modern earthquakes. As the first step to study historical earthquakes, we studied the seismic intensity distribution of recent earthquakes, in the Tohoku district, which occurred in the interval from 1926 to 1990. Results are summarized as follows.(1) The isoseismal contours for many earthquakes off the Pacific coast elongate to north and south, and the seismic intensity decays steeply across the line which is almost parallel to the volcanic front. We call this line “Steeply Decay Line of Seismic Intensity (SDLSI)”. On the contrary, the distribution of seismic intensity for shallow inland earthquakes doesn't show this tendency.(2) We investigated the seismic intensity attenuation in the Tohoku district and obtained the next formula, I=A-BXwhere, I is the seismic intensity, X the hypocentral distance. Coefficients A and B are expressed as follows:for earthquakes of G1, G2 and G3 (see Fig. 2)A=0.198+0.679M, A/B=-1332+299.9M (east side of SDLSI), A=0.944+0.589M, A/B=-1329+279.5M (west side of SDLSI).for earthquakes of G4A=-1.315+0.912M, A/B=-410+134.9M(3) For the earthquakes along the plate boundary, we defined relatively low- and high-frequency earthquakes according to the value of MJ-MI, where MJ is JMA magnitude and MI the one determined by comparing observed intensity attenuation data of each earthquake with a curve calculated from formulas in (2). The epicenteral distribution of low- and high-frequency earthquakes does not show clear characteristics. But, off Fukushima Prefecture region, there seems to be a boundary of the high-and low-frequency earthquake's distribution along the plate boundary of about 40km depth. The high-frequency earthquakes are found in the west side of the boundary.

著者

宇佐美 龍夫 小竹 美子 佐藤 泰夫

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.22, no.4, pp.313-317, 1970-02-28 (Released:2010-03-11)

参考文献数

5

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To make clear the features of the spectrum splitting due to the introduction of a soft solid core, the frequency and spectral amplitude of torsional oscillations are calculated for the modes with colatitudinal order number n from 2 to 9, assuming GUTENBERG-BULLEN A′ earth model. The only deviation from the G-B model is the assumption that the distribution of rigidity is constant in the core. The possibillity of estimating the rigidity of the core by the use of spectrum splitting was discussed.

著者

宇佐美 龍夫

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.28, no.2, pp.217-219, 1975-08-10 (Released:2010-03-11)

被引用文献数

1

著者

宇佐美 竜夫

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.21, no.2, pp.143-146, 1968-08-30 (Released:2010-03-11)

参考文献数

3

著者

宇佐美 竜夫

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.13, no.2, pp.97-112, 1960-07-30 (Released:2010-03-11)

参考文献数

6

---

The equation of equilibrium of a homogeneous and isotropic elastic body was solved in the prolate and oblate spheroidal coordinates for the cases of m=0, 1 and 2. The solutions consist of three parts: the first part (Eq. (17)) satisfy Δ=0 and ω=0, the second part (Eq. (18)) Δ=0 and ω≠0 and the third part (Eqs. (80), (82), (83)) Δ≠0 and ω≠0.

著者

宇佐美 竜夫

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.14, no.1, pp.18-28, 1961-03-25 (Released:2010-03-09)

参考文献数

8

---

It is clear from the equation of motion of elastic medium expressed in vector form that there are several different solutions (expressions) which satisfy the condition Δ=0 (§3).In this paper, 8 different expressions (at least 4 of which are mutually independent) are obtained (§4). Next, by using one of these solutions, the author got two independent solutions for a problem of motion in an infinite elastic medium when displacements (or stresses) are given on the wall of a cavity in that medium (§5). In such a problem it is proved that we cannot get unique solution as long as we use the so-called Sezawa's solution ((17), (18), (4)) only (§6).

著者

神田 克久 武村 雅之 宇佐美 龍夫

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.56, no.1, pp.39-57, 2003-06-02 (Released:2010-03-11)

参考文献数

30

被引用文献数

6

---

The method of the inversion analysis to evaluate the distribution of seismic energy radiated from an earthquake fault plane based on seismic intensity distribution data has been developed. The fault plane is divided into small sub-faults. The optimized seismic energy distribution of each sub-fault is calculated using the least square method to minimize the error between evaluated and observed seismic intensities.The energy distribution of a seismic fault is related to seismic intensity using the attenuation formula with equivalent hypocentral distance. The parameters of the attenuation formula are obtained from a regression analysis with measured seismic intensity data of recent moderate earthquakes.The forward analyses using an assumed model are performed to verify the accuracy of the inversion analysis and to evaluate the effect of factors such as the standard deviation of seismic intensity, constraint condition of inversion analysis and configuration of observation stations.Finally, the method is applied to the Showa Tonankai earthquake in 1944 and the Showa Nankai earthquake in 1946 and the result is compared with the tsunami and strong motion waveform inversion results to confirm the efficiency and applicability of the method.

著者

宇佐美 竜夫 狩野 京一 佐藤 泰夫

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.15, no.4, pp.261-269, 1962-12-25 (Released:2010-03-11)

参考文献数

1

---

It is known that the equation of motion for isotropic and homogeneous elastic medium has 8 solutions having different expressions which satisfy the condition Δ=0. Six of these solutions are found to be expressed by the linear combination of the other two which can be considered as the most basic ones. Some other revisions are made on the former paper (Zisin; vol. 14 (1961), pp. 18-28).

著者

佐藤 泰夫 宇佐美 竜夫

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.17, no.3, pp.167-169, 1964-09-25 (Released:2010-03-11)

参考文献数

1

著者

田中館 秀三 三松 正夫 今村 明恒

出版者

公益社団法人 日本地震学会

雑誌

地震 第1輯 (ISSN:00371114)

巻号頁・発行日

vol.16, no.10, pp.280-287, 1944-10-18 (Released:2010-11-17)

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本調査は, 国中館秀三君の依頼と指導とに依りて, 三松正夫君に依つて成されたものである。三松君は, 有珠山の東北麓, 壯轡村瀧之町の郵便局長を勤めて居られる。田中館君より編者への通信に據れば, 「同局長に依頼して, 山の異變に胴する時々の牀況を記録し, 或は之をスケッチして報告して貰ふごとにしたが, 既に數同の報告が同封の通り到來してゐる。同氏は, 南豊を能くするだけに, 其のスケッチには冩眞とは異なつた氣分が出てゐる。私留守中 (目下朝鮮へ出張) は, スケッチ等は直接先生 (今村) へ御送りするやう手筈するから, 然るべく雑誌地震へでも發表して下さらば幸甚, 云々」とある。成程, 記録は簡潔で, スケッチは摘要を旨とし, 遠景用でない普通の冩眞器に依つて撮影したものよりもわかり易い。有珠山活動の経過を迫跡するには眞に好個の資料と稻すべきである。乃ち其の好意に應ずることにし, 蛇足ではあるが, 前後及び中間に, 有珠活動の経過を挿み, 讃易いやうにした。

著者

今村 明恒

出版者

公益社団法人 日本地震学会

雑誌

地震 第1輯 (ISSN:00371114)

巻号頁・発行日

vol.6, no.12, pp.675-676, 1934-12-15 (Released:2010-03-09)

著者

今村 明恒

出版者

公益社団法人 日本地震学会

雑誌

地震 第1輯 (ISSN:00371114)

巻号頁・発行日

vol.11, no.12, pp.588-598, 1939-12-25 (Released:2010-03-09)

著者

今村 明恒

出版者

公益社団法人 日本地震学会

雑誌

地震 第1輯 (ISSN:00371114)

巻号頁・発行日

vol.8, no.2, pp.51-56_1, 1936-02-15 (Released:2010-03-09)

著者

梶川 昌三 山田 功夫 深尾 良夫

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.46, no.3, pp.229-235, 1993-12-14 (Released:2010-03-11)

参考文献数

5

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One of the largest different conditions between the nature and laboratory experiment of rock fracturing is strain rate. Conventional experiment at a constant strain rate may not simulate the precursory stage of seismic fracture, where strain rate is so low that any anomalous crustal deformation may occur by consuming the strain energy that has already accumulated rather than one newly supplied from the exterior. In order to simulate such a preseismic stage of the crust, we conducted a “zero strain-rate experiment” using Westary granite as a sample. The granite specimen is loaded at a constant strain-rate mode until stress reaches a level about 90% of the fracture stress. The bulk axial strainis then kept constant by servo-control to observe the time-variations of axial stress, local strains, dilatant strain and AE-activity.Initially the axial stress decays exponentially and then linearly until the sample is finally broken. Axial surface strain shows a different behavior at different locality; strain concentration occurs in the area near the final fault and strain relaxation in the area far from it. Very anomalous behaviors are observed in both the areas just prior to the final break. Some implications of these results are discussed in conjunction with the field observations of crustal deformation before earthquake occurrence.

著者

松澤 暢

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.4, pp.525-536, 1989-12-24 (Released:2010-03-11)

参考文献数

68

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Many later phases such as ScSp, PS, SP and SS converted or reflected at the upper boundary of a descending oceanic plate are frequently observed in a subduction zone. The location of the upper boundary has been estimated to be just above the deep seismic zone by the use of these phases. Moreover, from the analyses of the later phases such as PS and channel waves, it has been found that a low velocity layer exists on the surface of the plate. The most probable interpretation of the low velocity layer, at least in the shallow depths, is the descending oceanic crust.