著者

纐纈 一起

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.3, pp.325-331, 1989-09-24 (Released:2010-03-11)

参考文献数

16

被引用文献数

2

---

Some techniques used in statistics, such as the variable change method, the penalty function method and the gradient projection method, are introduced to determine the location of a hypocenter with a definitely non-negative depth. Numerical simulations are carried out to compare the efficiency of them by using synthetic arrival time data for a four-station seismic array. They demonstrate that the penalty function method with a proper weight is the most efficient. However, if we take an improper weight, it may lead to a negative depth or an invalid solution. Since the variable change method and the gradient projection method do not have such arbitrariness, those can be implemented more easily into hypocenter determination processes operated routinely. The demonstration with real arrival time data shows that the variable change method as z=h2 has practical efficiency.

著者

纐纈 一起 竹中 博士

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.3, pp.391-403, 1989-09-24 (Released:2010-03-11)

参考文献数

96

被引用文献数

1 4

---

We review recent theoretical studies on wave propagation in the near field of seismic sources. These include theories for horizontally layered media as well as those for irregularly layered media. Ray theory and its extensions are easily applied to arbitrarily inhomogeneous media, but they include serious approximations. The finite difference method is also flexible, but requires extensive computation. Except for these methods, we should note that all the methods currently available for irregularly layered media belong to the category of the method of weighted residuals.

著者

纐纈 一起 古村 孝志

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.55, no.2, pp.97-105, 2002-10-31 (Released:2010-11-17)

参考文献数

20

---

The significant attenuation of seismic motion in the west of the 2001 Geiyo earthquake is inferred from strong motion distributions, observed seismograms and their spectra. Since this attenuation is identified even in the distribution of borehole motions, that is assumed to arise in a deeper part like the mantle wedge. If we assume a low-Q zone in the mantle wedge, a strong motion simulation with Qs = 20-30 can reproduce the observations. This zone may be related to dehydration of the Philippine sea plate.

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.28, no.3, pp.331-346, 1975-10-10 (Released:2010-03-11)

参考文献数

17

被引用文献数

1 3

---

Five stations of the Tottori Microearthquake Observatory have supplied an amount of records of microearthquakes since June, 1965. They are very useful to investigate the characteristics of spatial and temporal distribution of microearthquakes. Using data from three stations MZT, OYT and IZT, a seismological bulletin has been compiled. It contains P, P-S and P-F times and directions of initial motions at three stations, the coordinates of foci calculated from data of three stations and magnitude of each shock determined from total duration (P-F time).From June, 1965 to December, 1973, 7346 earthquake foci have been determined. Their epicenters have been plotted on seismicity maps. One of significant results from them is that the close relation between active faults and alignments of epicenters has been recognized.Computed results of epicenters from data of the three stations have good accuracy comparing with those from five stations. Errors of hypocenters near to the network are less than 2km. Those of distant foci whose P-S times are larger than 10 seconds are less than 10km. Because of the important purpose to know the temporal distribution of microearthquakes, almost all data containing some reading values which do not have so good accuracy have been used for calculation.Frequency distribution of magnitudes shows the normal activity in this region. It also shows that distant shocks whose magnitude are larger than 2.0 and epicentral distances are about 150km, are detected by this network of three stations. Hypocenters whose magnitudes are larger than 1.0 have been detected in the near region around the network.

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.38, no.3, pp.459-461, 1985-09-25 (Released:2010-03-11)

参考文献数

1

著者

野田 弘 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.39, no.4, pp.635-643, 1986-12-25 (Released:2010-03-11)

参考文献数

8

---

Variations of the level of ground water were observed at four stations near the epicenter of the shallow earthquake (M4.6) which occurred in the southern part of the Lake Biwa which has been recently a low seismicity region.About ten days before the occurrence of the earthquake anomalous changes of the water level were observed. Considering the relation between the variation of water level and rainfall in the ordinary period these anomalous changes were precursors of the earthquake.Co-seismic steps of the water level were observed at two stations. One of them was a sudden ascent which was observed at the region where initial P motions were compressional. At another station which was in the dilatational P region sudden descents were recorded.Such characteristic variations of the ground water level are detectable by using deep wells when an earthquake occur conspicuously in the low seismicity region, even if its magnitude is small.

著者

尾池 和夫 三雲 健

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.1, pp.54-66, 1968-05-30 (Released:2010-03-11)

参考文献数

6

---

A multipartite seismometer array with a span of about 1km has been set up at one of the temporary stations for the observation of microearthquakes in Wakayama region, to examine the effects of local underground structure.The apparent velocity and direction of wave approach for about 200 microearthquakes were determined by means of least squares from arrival times of P waves at 5 recording sites, as well as from the conventional tripartite technique. Parameters computed from 4 selected tripartite nets show systematic deviations from the results of least squares in relation to the azimuth. A possible explanation for the azimuthal dependence and for average travel-time residuals for each of the recording sites would be that there exists an upward-warping interface in the shallow portion of the crust. Several kinds of later phases can be identified on seismograms between the initial P and S waves. Their apparent velocities and travel-times appear to be consistent with the interpretation that these phases may be SV waves converted from incident P waves or vice versa at the above interface.

著者

尾池 和夫 志知 竜一 浅田 敏

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.1, pp.75-94, 1975-04-10 (Released:2010-03-11)

参考文献数

4

著者

尾池 和夫 松村 一男 竹内 文朗 松尾 成光 清水 昇

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.29, no.2, pp.127-135, 1976-05-15 (Released:2010-03-11)

参考文献数

4

---

A new type of the ink-writing recorder for the continuous obsevration of earthquakes is developed. Main principles of this recording system are as follows.1. Recording paper size is as same as a standard from of the line-printer system of the computer.2. The recording paper is feeded by the similar method as the line-printer system.3. Two pen-galvanometers are drived at right angles to the feeding direction of the recording paper.4. The same signal that is recorded at the ending part of a line by one galvanometer is recorded at the beginning part of a next line by the other galvanometer.By these principles the recording pattern on the paper is designed to be convenient for analyses. Recorded papers by this new recording system are efficiently stacked in the standard shelves, easily used and can be conveniently copied.Using one case of standard recording paper which has two-thousands pages, continuous observatition of about five months can be done if the recording speed is 4mm/sec, the interval of recording lines is 2mm and the signal for two hours is recorded on a page.Various applications can be utilized by controlling the paper feeder by the trigger signals from the seismic waves.

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

---

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

---

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

---

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).