巻号一覧
24 巻 (1971)
- 4 号 p. 279-
- 3 号 p. 189-
- 2 号 p. 79-
- 1 号 p. 1-
前身誌
24 巻, 3 号
選択された号の論文の8件中1～8を表示しています
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渡辺 晃1971 年 24 巻 3 号 p. 189-200
発行日: 1971年
公開日: 2010/03/11
ジャーナル フリーSeveral formulas to determine the magnitudes of earthquakes with shallow foci from amplitude and focal distance in the regional range up to about 1, 000km, were newly derived by using the data observed at the Abuyama Seismological Observatory and its array stations, and compared in the cases from displacement and velocity seismograms.
The patterns of maximum amplitudes versus focal distances show that the manner of decay of the displacement amplitude is practically similar to that of velocity amplitude in the distance range up to 200km, but markedly different in the range over 200km, because the phase of the seismic wave corresponding to the maximum amplitude varies from the body wave to the surface wave at the focal distance around 200km and the long period surface wave is sharply cut off with the steep slope of the frequency response curve of the velocity seismograph.
The amplitude-distance curves at the close distance range up to about 40km, however, are folded in the case of displacement amplitude. This phenomenon may arise from the effect of exitation of refracted or reflected, or both phases having longer periods, resulting in an increase of about 0.3 in the magnitude value. Taking no account of these slight folds, the decay of the maximum amplitude is supposed to be nearly uniform throughout the distance range concerned. Thus, the decay factor, including the geometrical spreading, is estimated as r-1.73, which is just the same as in the Tsuboi's (1954) formula.
The periods corresponding to the maximum amplitude were found to increase according to the earthquake sizes alone, when the same type of phase was traced. On the basis of this finding, an attempt was made to infer the relation between the source factor of displacement spectral density and the magnitude.抄録全体を表示PDF形式でダウンロード (1100K) -
三東 哲夫1971 年 24 巻 3 号 p. 201-214
発行日: 1971年
公開日: 2010/03/11
ジャーナル フリーPlate tectonics has successfully explained the source of stress which generate earthquakes along the oceanic ridge and earthquakes inside “Benioff zone” beneath the continental side of the trench.
There are, however, other shallow earthquake areas with another type of epicentral distribution in the continents for which source of stress for earthquake generations has not been studied. These seismic areas are found in South Europe, Middle Asia, South Asia around Tibet Plateau, Africa and in North America. Shallow earthquakes in these areas are characterized by wide scattering in their epicentral distributions.
In the present paper, an suggestion was given from the view of plate tectonics on the source of stress which generate these continental shallow earthquakes. That is, the shallow earthquakes as well as the recent uplift of the mountain chains would both be caused due to the stress inside the continental plate the movements of which have been impeded.抄録全体を表示PDF形式でダウンロード (1493K) -
第二部 地震の規模別頻度分布大塚 道男1971 年 24 巻 3 号 p. 215-227
発行日: 1971年
公開日: 2010/03/11
ジャーナル フリーAt what stage of earthquake phenomena is the total amount of energy to be liberated by a particular event determined? Is it scheduled since long before the occurrence of that event, just before its outbreak or just after termination of disturbance?
Through detailed study of the operation of a simulator treated in the first part of this paper, the author was led to be interested in the plausibilty of the last case.
The basic idea is that the elastic stress energy spread over vast volume of rock medium cannot be liberated at an instant but must be released as a result of sequential progression of rupture which may be controlled by numerous factors such as stress concentration strength, inhomogeneity, distribution of flaws etc. in the medium.
The implication is that the amount of energy which is going to be liberated by a particular earthquake can only be told on the probabilistic ground until all energy release processes of that event are brought to termination. The observed magnitude-frequency relations of earthquakes are in general agreement with this argument.抄録全体を表示PDF形式でダウンロード (1245K) -
岡田 弘1971 年 24 巻 3 号 p. 228-239
発行日: 1971年
公開日: 2010/03/11
ジャーナル フリーA deep earthquake occurred in the SW part of Fukui Prefecture on 14 August 1967. This shock produced a clear longitudinal phase about 8 sec before the normal ScS phase at stations URA and KMU, Hokkaido. On careful examination of seismograms of other nearby deep earthquakes at KMU, it was found that similar forerunners were recorded on several seismograms. These forerunners may not be interpreted as PKiKP phases because of their time differences. A possible interpretation is the conversion from ScS to ScSp at some plane of discontinuity in the upper mantle. Assuming the vertical incidence of ScS waves and a velocity contrast at the discontinuity (the upper layer has a velocity 10% smaller than that of the lower layer), a region in which the conversion plane may be located is determined from the ScSp incident angle, the time difference, and the amplitude ratio. The conversion plane has a dip of about 35°-39° and is nearly parallel to the deep seismic zone. The conversion plane is located near the upper boundary of the deep seismic zone and may coincide with the boundary between the dipping high-Q, high-V zone and the landside low-Q, low-V zone. It is interesting that the seismic activity is low under this conversion plane, while the surface volcanism is present above this plane.抄録全体を表示PDF形式でダウンロード (1124K) -
根尾谷断層周辺の微小地震活動大井田 徹, 山田 功夫, 多田 堯, 伊藤 潔, 杉山 公造, 佐々木 嘉三1971 年 24 巻 3 号 p. 240-247
発行日: 1971年
公開日: 2010/03/11
ジャーナル フリーIn order to study the seismic activity of microearthquakes in the southern part of the Neo Valley fault, an observation was carried out in 1968 from September 27 to November 2. Seven observing stations were set near the four stations of Inuyama Seismological Observatory.
About 400 microearthquakes were recorded during this observation, but about 50 epicenters could be determined. Their magnitudes were less than 2.
Microearthquakes occurred most frequently in the southwestern side of the fault, especially in the area upheaved by the Nobi earthquake of 1891. On the contrary, very few earthquakes occurred in the northeastern side. The focal depths of these shocks were very shallow.抄録全体を表示PDF形式でダウンロード (592K) -
佐藤 泰夫, 小竹 美子, 嶋 悦三1971 年 24 巻 3 号 p. 248-265
発行日: 1971年
公開日: 2010/03/11
ジャーナル フリーSeismograms of JMA type strong motion seismograph (magnification 1.0, damping ratio 8.0 and natural period 6.0sec) have been scarcely used for a quantitative study of earthquakes because of the difficulty of actual treatment even when a good record is obtained. In this paper, a method of analysing such seismograms is proposed and tested. As an example, the seismograms of the Niigata earthquake (June 16, 1964) obtained by JMA at Tokyo was carefully analysed giving the correction of zero-line shifting, effect of a mechanical arm etc., and the ground displacement and velocity were calculated. Maximum displacement proved to be about 3cm and the velocity about 5cm/sec. Applying this ground motion to pendulums with the damping h=0.05 and the natural frequency 0.026 (0.013) 0.4cps, forced oscillation of each pendulum was calculated, and thus the response of structures with various frequencies was studied by the method of numerical simulation. By this procedure it becomes clear what kind of structure will or will not be shaken in the case of strong earthquakes and how the oscillation grows up and dies away. The maximum displacement (or velocity) was chosen from each curve and plotted as a function of natural frequency of the structure. For the periods around 5 seconds the displacement becomes maximum and is about 20cm (velocity about 20cm/sec for the period around 4 seconds). Seismic waves having the periods thereabouts are extremely important from the view point of engineering seismology, since the natural periods of many high rise buildings already constructed as well as now in blueprints are of that order.
A similar calculation was carried out for two earthquakes recorded by the DC3 strong motion seismograph at Matsushiro area in 1966, and the displacement, velocity, acceleration of the ground and the response of pendulums (structures) with various frequencies were calculated. For one of these two earthquakes, besides the above calculations, the displacement which is expected on the surface of a typical soft sediment (Toyosu, Tokyo) is calculated when the above displacement is given at the bottom of the soft layers. The surface displacement becomes several times as large as the original motion.
Acceleration spectrum of the Imperial Valley earthquake in 1940 observed at El Centro is shown together with the Niigata earthquake for reference.抄録全体を表示PDF形式でダウンロード (1669K) -
飯田 汲事1971 年 24 巻 3 号 p. 266-274
発行日: 1971年
公開日: 2010/03/11
ジャーナル フリーThere have been developed a number of relations between seismic wave energy E and the magnitude M of an earthquake. The general form of the relation is written as logE=α+βM. in which α, β are constants and M is the surface-wave magnitude. A number of relations were presented as given in Table 1 where α and β are listed. The relationship between α and β seems to keep linearity as shown in Fig. 1. This relation can therefore be expressed as α=(26.10±0.91)-(9.60±0.72)β for 5.3≤M≤8.5 (1) α=(19.11±0.70)-(4.59±0.40)β for -2.1≤M≤5.3 (2) An energy-magnitude relation for large earthquakes having magnitude larger than 5 seems to be different from that for small earthquakes having magnitude smaller than 5.
The lines expressing (1) and (2) intersect at the point α=12.66, β=1.40. Thus, a new magnitude-energy relation which is appropriate for both large and small earthquakes is obtained as logE=12.66+1.40M. By using the relations between α and β in (1) and (2), seismic efficiency factor f was obtained as 0.04-0.90 from some examples.抄録全体を表示PDF形式でダウンロード (792K) -
大塚 道男1971 年 24 巻 3 号 p. 275-277
発行日: 1971年
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (303K)
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