巻号一覧
25 巻 (1972)
- 4 号 p. 275-
- 3 号 p. 207-
- 2 号 p. 115-
- 1 号 p. 1-
前身誌
25 巻, 3 号
選択された号の論文の11件中1～11を表示しています
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川崎 一朗, 鈴木 保典, 佐藤 良輔1972 年 25 巻 3 号 p. 207-217
発行日: 1972/12/30
公開日: 2010/03/11
ジャーナル フリーSince the dislocation theory is introduced into the field of seismology, it has become possible to determine seismic source parameters, such as fault type, fault dimension, strike- and dip-angle, slip direction, rupture direction, rupture velocity, etc., from analysis of observed seismic waves. In these studies so far only surface wave data in far field are usually used because rather simple theoretical approach is possible for surface waves. It is easily supposed that seismic data in near field contain much informations on focal process than those in far field. Theoretical studies on seismic waves in near field, however, have not been thoroughly investigated as yet.
The object of this study is to clarify characteristics of seismic waves in near field generated from a double couple source with an arbitrary orientation. Expressions for Laplace transforms of surface displacements with respect to time are obtained in a cylindrical coordinate system and applying Cagniard's method exact transient solutions are found when source time function is a ramp-type. It is shown that the moving source solution can be obtained by accomplishing numerical integration of the point source solution with some transformation of axes.
In part I of this paper, mathematical expressions are derived and result of numerical computations and discussions are presented in part II.抄録全体を表示PDF形式でダウンロード (730K) -
羽鳥 徳太郎1972 年 25 巻 3 号 p. 218-224
発行日: 1972/12/30
公開日: 2010/03/11
ジャーナル フリーBased on tide gauge records at Hokkaido and Sakhalin, a tsunami accompanying the southwestern Sakhalin earthquake on Sept. 6, 1971 (M=6.9, JAM) is investigated. The southern end of the tsunami source is located at about 15km north of Moneron I. (Kaiba I.). The initial motion of the tsunami waves was in an upward direction at most stations, suggesting the uplift of the sea bottom in a southern part of the tsunami source. The source dimension of tsunami is inferred to be 70km long in the NE-SW direction and the area is 2.2×103km2. The tsunami energy of approximately 3×1018 ergs is calculated from a first wave (crest and trough) observed at Wakkanai. This value corresponds to the lower limit of Imamura-Iida's tsunami magnitude m=0.5. The tsunami magnitude, in turn, is estimated by the author's method, which makes use of the wave attenuation with distance. The average vertical displacement of 20cm might have occurred in the source to account for the estimated tsunami energy. Generally speaking, the present tsunami is of the standard magnitude in the statistical relation to earthquake magnitude. It is noticed that the tsunami fronts arriving the Shakotan peninsula have propagated in deep waters and the wave amplitudes are relatively high due to the refractive effect.抄録全体を表示PDF形式でダウンロード (616K) -
山科 健一郎, 竹内 均1972 年 25 巻 3 号 p. 225-231
発行日: 1972/12/30
公開日: 2010/03/11
ジャーナル フリーScandinavian region is uplifting and Indian region is a stable shield area, so we may expect negative gravity anomaly in the former region and no systematic anomaly in the latter. Against these expectations, we have no systematic negative anomaly in Scandinavia and negative anomaly in India, if the anomalies are calculated basing upon the standard gravity formula including only (l=2 and 4, m=0) term in the spherical harmonic expansion. It may be, however, that processes responsible to the Scandinavian uplift and the Indian geology occur in shallower depth (probably in the C layer, asthenosphere) and that mass anomaly responsible to the anomaly of rather longer wave length (or smaller wave numbers l and m) exists deep (probably in the C and D layers, mesosphere) within the earth. If such is the case, in order to get gravity anomaly closely related to geology, we must take as the standard gravity not only (l=2 and 4, m=0) term but also higher order terms in the spherical harmonic expansion. In short we must choose the standard gravity formula so as to get gravity anomaly which is agreeable with other geophysical and geological observations.
Studies are made from the above point of view. Gaposchkin and Lambeck's data on the spherical harmonic expansion of geoidal undulations are used. It is our tentative conclusion that by including terms up to (l=8, m=8) we get anomalies which are more agreeable with geology than the standard gravity formula.抄録全体を表示PDF形式でダウンロード (766K) -
伊神 輝, 安久 勉, 青木 治三1972 年 25 巻 3 号 p. 232-242
発行日: 1972/12/30
公開日: 2010/03/11
ジャーナル フリーAn observation of microearthquakes was carried out near the Atera Fault for two and a half months, from July 14 to October 2, 1971, since the fault has been known as one of the most active faults in Japan.
In the south-western side of the Atera Fault, the focal depths of earthquakes were deeper than 30km, that is, earthquakes occurred in the mantle but not in the crust. In the northeastern side, however, only a few earthquakes were detected. Although three direct analogue recording systems of high sensitivity were used near the fault, very few earthquakes could be located near the fault. A comparison of daily frequency of earthquakes near the NeoValley Fault with the present observation showed that the seismicity near the Atera Fault was undoubtedly lower than that near the Neo-Valley Fault. The same tendency has been also observed for larger earthquakes. Number of earthquakes detected at one of the three stations was exceptionally large, though the sensitivity was the same for all stations. But most of distant earthquakes were equally detected.
Considering these facts, it might be concluded that the present seismic activity is very low and, in addition, seismic waves of high frequency are attenuated in the crust near the Atera Fault. Some focal mechanisms of microearthquakes were calculated. The pressure axis thus obtained was E-W direction as in the case studied by MATSUDA (1969) and ICHIKAWA (1971).抄録全体を表示PDF形式でダウンロード (1078K) -
平柴観測点の傾斜変化, 1967～1971年大竹 政和, 山田 重平, 小林 勝1972 年 25 巻 3 号 p. 243-253
発行日: 1972/12/30
公開日: 2010/03/11
ジャーナル フリーAt Nagano City, Central Japan, ground tilt was continuously observed with a set of water-tube tiltmeter and an Ishimoto type silica tiltmeter (horizontal pendulum) for four years from April 1967 to May 1971.
General trend of the tilt shows a secular ascending of the basement to N13°E direction. The movement not only qualitatively but quantitatively corresponds to an unusual upheaval of the crust at northeastern part of Nagano City, which was found by revision of precise levelling. This local upheaval was accompanied with a considerable activity of smaller earthquakes. Our study demonstrates that such a short-span observation of ground tilt can successfully supplement discrete data from levelling, if the observation is carefully planned. Horizontal pendulum tiltmeters are much more convenient to be installed compared with water-tube tiltmeters, but the tilt resulted from the former instruments, θS does not necessarily coincide with that from the latter, θW. In our case, θS is about five times as large as θW though the azimuth of the tilt variation is harmonious one another. A model is offered in order to interpret such amplification of the ground tilt.
Tilt variations just after larger Matsushiro earthquakes were investigated, but we could not detect any tilt steps attributed to the dislocation at the origins.抄録全体を表示PDF形式でダウンロード (973K) -
―関東地震の場合―佐藤 泰夫, 小竹 美子1972 年 25 巻 3 号 p. 254-262
発行日: 1972/12/30
公開日: 2010/03/11
ジャーナル フリーThe origin of earthquake ordinarily determined in seismology is probably the point where the earthquake motion first occurred. On the other hand from the viewpoint of earthquake engineering the center of the collapse of houses and other structures has even larger meaning than the above point seismometerically obtained. The destruction, however, is affected by a number of conditions such as the foundation and topography, though generally speaking, it will be a decreasing function of the distance from the center point.
The data studied in the present paper is the ratio of the collapsed houses in Tokyo and surrounding prefectures reported in “REPORTS OF THE IMPERIAL EARTHQUAKE INVESTIGATION COMMITTEE No. 100, A” (Tokyo 1925) by Dr. T. MATUZAWA. This percentage, y, of the destructed houses, is transformed into x by the MONONOBE formula, y=100·1/√2π∫x-∞exp(-t2/2)dt (1) and the following expression connecting x and the distance r is assumed, namely x=alog10r+b=f(r). (2) The coefficients a and b are determined by means of the least square method as a=-2.786, b=3.29 (unit of distance=km) (3) where the depth of focus is assumed to be 15km.
By the successive approximation, the most probable location of the center of destruction was determined in the sense of least squares, starting from the 1st approximation point given in Rika-Nenpyo; (139.3°E 35.2°N). (5) The result came out as (139.46°±0.02° 35.19°±0.01°). (6) If the depth of focus is assumed to be zero, the coefficient become a=-2.432, b=2.590 (8) and the center is (139.44°E±0.02°, 35.20°N±0.01°). (7) Anyway the resultant location is about 15km east of the first assumed point.
The method (program) can be applied for finding the center of any distribution given by a decreasing function f(r), in which r is the distance between the center and the field point.抄録全体を表示PDF形式でダウンロード (501K) -
茂木 清夫1972 年 25 巻 3 号 p. 263-264
発行日: 1972/12/30
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (263K) -
阿部 司1972 年 25 巻 3 号 p. 265-266
発行日: 1972/12/30
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (222K) -
竹内 均, 藤井 直之, 菊地 正幸1972 年 25 巻 3 号 p. 266-268
発行日: 1972/12/30
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (379K) -
竹内 均, 菊地 正幸1972 年 25 巻 3 号 p. 268-269
発行日: 1972/12/30
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (267K) -
竹内 均1972 年 25 巻 3 号 p. 270-271
発行日: 1972/12/30
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (208K)
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