巻号一覧
29 巻 (1976)
- 4 号 p. 323-
- 3 号 p. 223-
- 2 号 p. 93-
- 1 号 p. 1-
前身誌
29 巻, 1 号
選択された号の論文の9件中1～9を表示しています
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井元 政二郎1976 年 29 巻 1 号 p. 1-13
発行日: 1976/03/10
公開日: 2010/03/11
ジャーナル フリーIn the study of the source process of an earthquake, it is important to know the position of the main shock relative to the aftershock area. The epicenters of the large earthquake on August 11, 1969 and several foreshocks in a minute before are determined by JMA (Japan Meteorological Agency), USCGS (U. S. Coast and Geodetic Survey) and ISC (International Seismological Center). But, different locations are derived from each determination to the aftershock area, and the apparent rupture velocity between the last foreshock and the main shock, calculated from the data of USCGS and ISC, is higher than 10km/s. It is probable that the later phases due to the foreshocks disturb the initial arrival due to the main shock.
In the present paper, the locations of the main shock and foreshocks are determined precisely by simple least squares procedure. From precise locations, the main shock seems to start from a point on the landward edge of the aftershock area. This relation between the epicenter of the main shock and the aftershock area is similar to those of other earthquakes which occurred recently along the Kurile trench near Hokkaido. The apparent rupture velocity turns out to be about 3.2km/s.抄録全体を表示PDF形式でダウンロード (1063K) -
伊神 輝1976 年 29 巻 1 号 p. 15-24
発行日: 1976/03/10
公開日: 2010/03/11
ジャーナル フリーOn November, 29, 1974, a 465.5kg explosion was made by Geological Survey of Japan for measuring the secular variation of seismic wave velocity in the Kanto district. This explosion was used by the present author for investigating the seismic wave attenuation and the crustal structure beneath the Izu Peninsula. Seven temporary stations were installed by the author for these purposes in the Izu Peninsula and to the west of the Suruga Bay. The data at five stations among seven and at other five stations, operated by others at that time, were obtained.
The results are as follows; (1) The velocity amplitude decay is represented as Δ-3 in the frequency range from 5Hz to 10Hz, where Δ is the epicentral distance. (2) The travel time delay at the stations to the west of the Suruga Bay are as large as 1.0 to 1.5sec. compared to those estimated from the travel times in the Izu Penisula. These results show that the attenuation factor in the crust beneath the Izu Peninsula is larger than those in the other regions and the crustal structure beneath the Suruga Bay and the Izu Peninsula is complicated.抄録全体を表示PDF形式でダウンロード (871K) -
微動の卓越周期と地下構造の関卓成瀬 聖慈, 出原 孝示, 竹内 文朗, 太田 裕, 鏡味 洋史, 後藤 典俊, 塩野 計司, 工藤 一嘉, 坂尻 直巳1976 年 29 巻 1 号 p. 25-32
発行日: 1976/03/10
公開日: 2010/03/11
ジャーナル フリーThis is a continuation of the research on the observation of long-period microtremors for elucidating ground characteristics during an earthquake. Results of observation along a line of about 17km from Hachinohe to Misawa cities in Aomori Prefecture, Japan, are outlined in this paper. Essential efforts were made on the affirmation and extension of the conclusions in the previous paper—a systematic change of predominant periods of microtremors along a 5km-line from 0.7sec at the point close to the outcrop of the bed rock to 2.5sec at the strong motion accelerograph site, and the relation of the predominant periods to the deeper underground conditions. Instruments, observations, and data processings are almost the same to those in the first paper.
The results obtained are as follows. First, the reobservation of the microtremors along the same line revealed a similar and very systematic change of the predominant periods, though the spectrum of the input motions to the ground layers seemed significantly diferent. Second, the observation extended as far as Misawa city brought the longest predominant period of 3.5sec at the end point, and produced the conclusion that the changes of the period of microtremors were very responsible to the undulation of the bed rock formation. The layer thickness corresponding to 3.5sec in period was estimated as about 500m.
This investigation strongly suggests the importance of knowing the ground dynamic characteristics down to 500-1000m in depth for the aseismic construction of large-scale structures and thus the significance of observation of the long-period microtremors.抄録全体を表示PDF形式でダウンロード (709K) -
光川 銀三, 道広 一利, 藤井 和成, 中野 正吉1976 年 29 巻 1 号 p. 33-45
発行日: 1976/03/10
公開日: 2010/03/11
ジャーナル フリーSpherical cavity in an infinite elastic medium is taken as a model of actual wave-source in small explosion and the radiated disturbances are analytically obtained in the case when a pressure with axially symmetric distribution is loaded over the surface of cavity. Scholte's potentials are used to represent spherical components of displacement and P and SV pulses at distant points are then obtained in the forms of infinite series. Some discussions are made, particularly on the sources of Fig. 2, in order to get the approximate expressions leading to the accurate results as possible in numerical calculations.
The wave-forms and directivities of pulses from two kinds of sources shown in Fig. 2 are numerically computed, when the time dependence of pressure, p(t), at the source is assumed to be e-t and te-t+1(t>0), respectively.抄録全体を表示PDF形式でダウンロード (910K) -
多田 堯1976 年 29 巻 1 号 p. 47-53
発行日: 1976/03/10
公開日: 2010/03/11
ジャーナル フリーThe subcrustal structure beneath the Kanto plain was studied by geological and gravity data. Bouguer gravity anomalies were corrected by the thicknesses of the sedimentaly layers, and then Bouguer gravity anomalies were reduced to the basement. This correction coresponds to the Bouguer's correction.
The reduced gravity anomaly represents the structure under the basement if the thicknesses of the sedimentaly layers are correct. But the depthes of the basements (the thicknesses of the sedimentaly layers) are not always so correctly measured that the reduced gravity anomalies will represent the structure beneath the basement and the structure of the basement as well.
The reduced gravity anomaly map shows that the high gravity belt, or the anomalous gravity gradiant zone exists along the north side of the Tama-gawa river and the low garvity zone exists north side of the high gravity belt around the Sayama hill.
These gravity anomalies also show that the geological tectonic line (the fault) lies along the north side of the Tama-gawa river with the drop in its north-east side near the Sayama hill. This fault passes the western part of Tokyo from north-west to south-east.抄録全体を表示PDF形式でダウンロード (701K) -
太田 陽子, 松田 時彦, 長沼 和雄1976 年 29 巻 1 号 p. 55-70
発行日: 1976/03/10
公開日: 2010/03/11
ジャーナル フリーSeven steps of marine terraces are well developed on the Ogi Peninsula, Sado Island. The seventh (lowest) one is a raised abrasion bench less than 2m high, emerged at the time of the destructive earthquake of 1802, hence it is named the 1802 terrace. The sixth terrace is about 2-4m high, and probably was formed at the time of Holocene transgression. Higher five terraces (Pleistocene terraces V-I) are well preserved over the most part of the peninsula and have the height of 32-40m, 70-55m, 94-118m, 123-137m and more than 165m, respectively.
The height of former shorelines represented by shoreline angle of each terrace shows that all the terraces tilt northward. Generally, the higher the terrace, the larger the amount of tilting. However, the tilt of the lowest two terraces (the 1802 and Holocene terraces) is almost the same, ca. 1.5′. This indicates that the 1802 tilting caused by the earthquake was a first event after the formation of the Holocene terrace of ca, 6, 000 years old and the recurrence interval of the events was more than 6, 000 years. A uniform regional difference of 2m in height between these two terraces is probably interpreted as a superposed result of the eustatic lowering of sea level and a regional uplift during last 6, 000 years.
It is possible to estimate the average intervals of earthquakes after the terrace formation by comparing the tilting rate of all Pleistocene terraces with that of the 1802's. Thus, the average recurrence intervals are estimated at about 8, 600 years since Terrace III was formed and about 5, 000 years since Terrace IV was formed. These values are consistent with the interval of more than 6, 000 years which is estimated from tilt of the 1802 and the Holocene terraces. It is concluded, therefore, that the earthquake has taken place repeatedly in a similar manner with a recurrence interval of about 5, 000-9, 000 years during at least last 105 years.
Uplift and northward tilting of the Ogi Peninsula at the time of the 1802 earthquake (Magnitude 6.6) is significantly larger than those of Awa-shims at the Niigata earthquake of 1964 (M 7.4), though its magnitude was smaller.
This fact and the limited areal deformation by the 1802 earthquake imply that the epicenter of this earthquake was located very close to the coast of the Ogi Peninsula, probably within a few kilometers off Shukunegi. A reverse faulting is inferred to have occurred along a northward-dipping fault plane at the 1802 earthquake.抄録全体を表示PDF形式でダウンロード (3987K) -
脇田 宏, 野津 憲治, 中村 裕二, 森岡 正名, 野口 正安1976 年 29 巻 1 号 p. 71-81
発行日: 1976/03/10
公開日: 2010/03/11
ジャーナル フリーMeasurements of radon concentration in groundwater were performed in the lower Tamagawa area where an abnormal ground upheaval phenomenon has been observed for five years since 1971.
The measurement technique mainly used in this study is the method of a toluene extraction-liquid scintillation counting. Meanwhile, radon concentration in groundwater has been continuously monitored with a ZnS scintillation detection system.
Radon concentration of groundwater in the region ranges from 2 to 3×10-10Ci/l. During the period between February, 1975 and February, 1976, no significant change of radon concentration was observed.抄録全体を表示PDF形式でダウンロード (2829K) -
岡田 義光1976 年 29 巻 1 号 p. 83-86
発行日: 1976/03/10
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (349K) -
池上 良平1976 年 29 巻 1 号 p. 86-87
発行日: 1976/03/10
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (255K)
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