巻号一覧
40 巻 (1987)
- 4 号 p. 513-
- 3 号 p. 329-
- 2 号 p. 145-
- 1 号 p. 1-
前身誌
40 巻, 4 号
選択された号の論文の16件中1～16を表示しています
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（山梨県芦川井のボーリングコア試験結果）佐藤 春夫, 塚原 弘昭, 池田 隆司1987 年 40 巻 4 号 p. 513-518
発行日: 1987/12/25
公開日: 2010/03/11
ジャーナル フリーThe non-uniform and non-stationary rupture of a fault is controlled by the inhomogeneous distribution of elastic moduli, stress, and fracture strength. The excitation of high frequency seismic waves is essentially dependent on the spatial fluctuation of these parameters. The spatial distribution of the fracture strength of rock, however, has not been experimentally measured yet. Not only the in-situ stress by hydraulic fracturing and the elastic moduli by well log at a well in Ashigawa-mura, but we measured the uniaxial compressive fracture strength of boring core samples of porphyrite. Forty-five samples were taken between 125 and 195m in depth with sampling intervals of 1.58±0.18m. The autocorrelation function of the uniaxial compressive fracture strength, which statistically characterizes the spatal inhomogeneity, was 30% at the nearest neighbor. This correlation is the same order as those of acoustic and density well log data.抄録全体を表示PDF形式でダウンロード (734K) -
鉛直方向の応力状態及び広域応力場池田 隆司, 塚原 弘昭1987 年 40 巻 4 号 p. 519-531
発行日: 1987/12/25
公開日: 2010/03/11
ジャーナル フリーIn-situ stress measurements using a hydraulic fracturing technique were conducted at two sites, Tsuru City (TR) and Ashigawa-mura (AS), to the southeast of the Kofu basin in Yamanashi Prefecture. The distance between TR and AS is about 16.5km. The depths of the wells for the experiments are 450m and 200m, respectively. Maximum and Minimum horizontal compressive stresses, SHmax and SHmin, were obtained successfully in 4 and 12 depths, respectively. The stress-depth relationship between 120m and 200m was investigated in detail at the AS site. After examination of the experimental results, the following stress state was elucidated: both SHmax and SHmin tend to increase with depth. At the AS site, a stress concentration zone exists at a depth of about 170m with a width of about 30m. However, a stress relaxation zone is evident at the TR site.
The direction of SHmax, which is given by the azimuth of the hydraulic fractures, was obtained at 3 points in the TR borehole and 4 points in the AS borehole by using impression packers. Both sites have the SHmax direction, N60°±20°W. We investigated the 3-dimensional stress state in this area with these results and with the data from the focal mechanisms of micro-earthquakes. Synthetic analysis of these data revealed that stress direction is understood in terms of the compressive stress in the Eurasian plate produced by the relative north-westward movement of the Philippine Sea plate.抄録全体を表示PDF形式でダウンロード (1450K) -
長谷川 昭, 山本 明, 海野 徳仁, 高木 章雄, 佐藤 孝雄1987 年 40 巻 4 号 p. 533-540
発行日: 1987/12/25
公開日: 2010/03/11
ジャーナル フリーSeismicity off Fukushima Prefecture is extremely high and many microearthquakes are located in this region by the seismic network of Tohoku University. Since the stations of Tohoku University are located in land area far from the focal region, the accuracy of focal depth is quite low for these shallow earthquakes. The means of improving the accuracy of focal depth is to make seismic stations in this region beneath the sea.
Continuous seismic observation by hydrophones has been carried out at a platform which was constructed for producing natural gas. The platform is located 40km off the coast of Iwaki, Fukushima Prefecture. Output seismic signals from hydrophones are transmitted to the Observation Center in Sendai via the relay station by using radio telemetry. P arrival data at the hydrophone station improve strikingly the accuracy of focal depth of shallow earthquakes occurred off Fukushima Prefecture, which enables us to estimate precisely the location of the upper boundary of the descending Pacific plate. The hydrophone data also made possible to identify the fault plane of the shallow event with magnitude 6.7 which occurred in this region on February 6, 1987.抄録全体を表示PDF形式でダウンロード (929K) -
向山 広, 茂木 透, 木村 強1987 年 40 巻 4 号 p. 541-549
発行日: 1987/12/25
公開日: 2010/03/11
ジャーナル フリーA study of regional tectonics using the lineament map drawn from Landsat TM (Thematic Mapper) images was conducted for the southern part of Chubu district, Central Japan. Many long lineaments appeared along boundaries of tectonic blocks which are characterized by directional orientation of small lineaments. Tectonically significant NE-SW lineaments crossing Akaishi Mountains were specially obtained.
It was found that the NE-SW lineaments coincide with geological or active faults in Akaishi Mountains and South Fossamagna areas, but they are not along with the sedimentary structure of the Paleogene and Neogene formation distributed in these areas. In the north side area of the NE-SW lineaments, main directions of small lineaments are N-S or E-W and seismic activity in the crust is low. In the south side area, on the contrary, the main directions of them are N-S or NE-SW and seismic activity is high. Moreover, the most north one of the NE-SW lineaments agrees with the boundary of the principal axis of the seismic stress. Many earthquakes, of magnitude more than 4, also occurred on the NE-SW lineaments in Akaishi Mountains. Therefore, the NE-SW lineaments are considered to reflect the active fracture zones and extend to the Median Tectonic Line.抄録全体を表示PDF形式でダウンロード (1195K) -
古川 信雄1987 年 40 巻 4 号 p. 551-560
発行日: 1987/12/25
公開日: 2010/03/11
ジャーナル フリーExtending the method of Joint Hypocenter Determination, we devised a new method to determine hypocenters, station corrections and a seismic velocity in the source region of shallow earthquakes simultaneously. Travel times of initial P waves of earthquakes occurring in a small area are analysed in this method.
We have applied this method to subcrustal earthquakes with depths of 20-40km in several small regions in the Tokai district, and P velocities of 6.8±0.3km/s were obtained. Since this value is quite similar to that in the main layer of the oceanic crust, we can conclude that these subcrustal earthquakes in the Tokai district occur within the subducted oceanic lower crust of the Philippine Sea plate.抄録全体を表示PDF形式でダウンロード (1139K) -
八木断層, 山田断層の検討と近畿北西部のブロック構造桂 郁雄, 西村 進, 赤松 信, 松田 高明, Edy M. ARSADI1987 年 40 巻 4 号 p. 561-573
発行日: 1987/12/25
公開日: 2010/03/11
ジャーナル フリーGeologic and geophysical surveys were carried out in the Yagi fault and the Yamada fault areas of the northwestern part of Kinki district.
Two lines of ELF-MT sounding and four areas of γ-ray survey show that a large fracture zone of the Yagi fault exists in Sekinomiya-cho area, Hyogo Prefecture. The fracture zone is about 200 to 300m wide and composed of some of micro and subsidiary faults. The main fault line is deduced from the outcrops and topography besides the evidence of geophysical surveys. The main fault is approximately corresponding to the geologic boundary between the Hokutan group and the serpentinite body. The remarkable character of this fault is few occurrence of micro earthquakes in spite of the large fracture zone.
Two lines of ELF-MT sounding, three lines of γ-ray survey and some outcrops of the fault show that the Yamada fault extends westward in Nodagawa-cho area, Kyoto Prefecture. This and former surveys suggest that the Yamada fault system with about 3km wide is composed of many small faults trending E-W between the Nakafuji fault, as the north border, and the extension of Yamada fault, as the south border.
The geologic and seismic characteristics distinguish seven tectonic zones in the northern part of Kinki district, north of Median Tectonic Line. The boundary of tectonic zones often coincides with large transcurrent fault systems. The Yagi and the Yamada faults take on carts of the boundary of tectonic zone system.抄録全体を表示PDF形式でダウンロード (1706K) -
寒川 旭, 岩松 保, 黒坪 一樹1987 年 40 巻 4 号 p. 575-583
発行日: 1987/12/25
公開日: 2010/03/11
ジャーナル フリーNumerous open cracks filled by sand were found on the river bed of the Kizu river. The observation and investigating results are summarized as follows.
1) Many of the cracks extend in N-S or E-W directions along ditches which had been excaved before the 14th century. It is believed that these cracks were easily formed along the ditches as weak zone.
2) It was confirmed that sand in cracks was spouted by earthquake shaking from the sand layer 1.5-2m below.
3) Strata below the cracks are severely deformed and generally warped upward along the cracks.
4) In some places, sand boiling spread over the burned surface and covered many footprints of men and cattle. It is considered that earthquake occured just after they had passed through.
5) Cracks and sand boilings have been covered by sediments after the 18th century showing that the earthquake occured during the 14-18th century. This district was struck by large two earthquakes of 1596 and 1662. The facts of sand boilings caused by these earthquakes have been also discribed in historical documents. We concluded that earthquake traces impressed in this site are the results of these earthquakes.抄録全体を表示PDF形式でダウンロード (3147K) -
スラブペネトレーションとマントル対流本多 了1987 年 40 巻 4 号 p. 585-592
発行日: 1987/12/25
公開日: 2010/03/11
ジャーナル フリーWe consider the possibility of two-layer mantle convection with a soft boundary lying between the upper and the lower mantle. If the activation energy and volume of creep do not change much with pressure, we may expect the low viscosity zone just beneath the boundary. The transformational superplasticity which will accompany with phase changes may also result in a soft boundary.
The coupling between the upper and the lower convections is controlled by two opposing factors, that is, thermal and mechanical factors. We conducted simple numerical calculations to investigate the effects of the viscosity near the boundary on the mode of coupling. If the viscosity at the boundary is less than 1/100 times that of the surrounding area, the thermal effect dominates the coupling. Such a thermal coupling may explain the recent seismological observations suggesting the existence of aseismic slabs beneath the subducting plates. We also discuss a possible seismic method to determine which of the whole and the layered mantle convections is the preferred mode of mantle flow.抄録全体を表示PDF形式でダウンロード (909K) -
(2) 台湾から華南へいたる地域趙 志新, 松村 一男, 尾池 和夫, 石川 有三1987 年 40 巻 4 号 p. 593-604
発行日: 1987/12/25
公開日: 2010/03/11
ジャーナル フリーMutual relations of the temporal variation of seismicity in the long period in various regions in East Asia were analyzed. Time series of events in South-East China, South-east coast of China, Taiwan and Ryukyu regions were compared with each other.
The seismicity of each region was high in the period from 1550 to 1650. Then a quiet period lasted until 1900. From 1900 an active period began and continued up to the present. Concentrated activities were found in the South China, South-east coast of China and Taiwan regions in a short time range around 1830 during the quiet period.
The seismicity of each region was high from 1900 to 1940, and a quiet period was found in the middle of the 1940s. From 1960 the active period began and has continued up to the present. It seems that short period variations superpose on the long period variation. These short period variation in all regions also correlate to each other.
Synchronous variations of seismicity in these regions are implicated that the earthquake generating stress fields from Taiwan to South China are found under the common tectonic conditions. Correlations of temporal variations of seismicities in Taiwan, Ryukyu and South China suggest that there are transmissions of tectonic forces from the subduction of Philippine Sea plate along the Ryukyu trench and the collision between the Philippine Sea and Eurasian plates along Taiwan Island to South China through the East China Sea and the Taiwan Strait.抄録全体を表示PDF形式でダウンロード (1422K) -
地震発生時期力武 常次1987 年 40 巻 4 号 p. 605-617
発行日: 1987/12/25
公開日: 2010/03/11
ジャーナル フリーAnalysis of precursor time-main shock magnitude relationship and/or frequency distribution of precursor time makes it possible to evaluate the probability of earthquake occurrence within a specified period of time provided a good many data of earthquake precursor of a particular discipline are available. The approach is purely empirical basing on the nature of precursor data so far obtained in Japan.
The probabilities thus estimated are different from discipline to discipline of precursor. For a magnitude 7 earthquake, for instance, geodetic and geomagnetic signals provide a precursor of long term, the peak of probability maximum for earthquake occurrence within 1 day occurring several hundred or thousand days after the signal appearance. Meanwhile, the probability peaks for radon and other geochemical elements, underground water/hot spring and the like occurs much earlier forming a group of precursors of short term.
When a number of precursors are observed one by one, changes in the synthetic probability of earthquake occurrence can be estimated according to the existing formula [UTSU (1977)]. As an example, such probability changes with time are estimated making use of the precursor data for the 1978 Izu-Oshima Kinkai earthquake of magnitude 7.
It is interesting to see that the synthetic probability generally increases as time goes on. However, the probability discontinuously lowers when a long-term signal happens to appear after short-term signals. When the period for probability estimate is taken shorter, the probability curve fluctuates considerably making the prediction of occurrence . time difficult. Such difficulties seem to be avoided for a medium-term prediction for which a period of having the main shock within 100 days or so is assumed.
One of the most difficult problems in the probability estimate is the point that we do not know whether or not a signal really represents a precursory one. The rate of false signals against the total signals has been estimated only for land uplift and foreshock precursors. In the circumstances, the said rate for other precursor disciplines is arbitrarily assumed as 1/20 in the estimate in this paper. Such a value should be improved in the future with the accumulation of precursor data.抄録全体を表示PDF形式でダウンロード (1129K) -
松橋 ゆかり, 油川 健, 佐藤 裕1987 年 40 巻 4 号 p. 619-622
発行日: 1987/12/25
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (402K) -
(2) 住家復旧過程の簡単なシミュレーション鏡味 洋史, 大橋 ひとみ, 太田 裕1987 年 40 巻 4 号 p. 623-625
発行日: 1987/12/25
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (430K) -
―おもに負傷者発生率と震度の関係について―塩野 計司, 小坂 俊吉1987 年 40 巻 4 号 p. 625-628
発行日: 1987/12/25
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (539K) -
伊豆海嶺西縁でのフィリピン海プレートの厚さについて瀬野 徹三1987 年 40 巻 4 号 p. 629-632
発行日: 1987/12/25
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (457K) -
末次 大輔1987 年 40 巻 4 号 p. 633-644
発行日: 1987/12/25
公開日: 2010/03/11
ジャーナル フリーThe fate of lithospheric slabs descending along island arcs is an important issue on mantle dynamics. The slab penetration into the lower mantle implies the flow of upper mantle material into the lower mantle. Travel time anomalies observed from deep-focus earthquakes suggest the extension of the high velocity slabs into the lower mantle in the western Pacific subduction zones. The depth extent of the slabs is not definitely determined by using only travel time data, because the path coverage of body waves is bad in the lower mantle below subduction zones. Observations of anomalously broad and complex S waveforms from deep-focus earthquakes are consistent with the lower mantle slab penetration hypothesis. Lower mantle slab models which quantitatively explain the observed waveform broadening have not been derived. Appropriate methods for calculation of theoretical seismograms in strongly heterogeneous media such as subduction zones are required to analyze the observed waveforms and confirm the hypothesis. Deployments of global network of broadband seismographs with wide dynamic range are also essential to reveal the lower mantle slab structure.抄録全体を表示PDF形式でダウンロード (1515K) -
越川 善明1987 年 40 巻 4 号 p. 645-652
発行日: 1987/12/25
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (12530K)
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