巻号一覧
39 巻 (1986)
- 4 号 p. 525-
- 3 号 p. 351-
- 2 号 p. 201-
- 1 号 p. 1-
前身誌
39 巻, 3 号
選択された号の論文の14件中1～14を表示しています
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安山岩中で発生するAEの発震機構佐藤 隆司, 出原 理, 西沢 修, 楠瀬 勤一郎1986 年 39 巻 3 号 p. 351-360
発行日: 1986/09/25
公開日: 2010/03/11
ジャーナル フリーBy using P-wave first motions, focal mechanisms of 61 acoustic emission (AE) events in a cylindrical sample of Yugawara andesite were determined during triaxial compression under a confining pressure of 20MPa. The AE events were divided into the following two groups in terms of the space-time distribution of hypocenters. Group-I: the randomly distributed events. Group-II: the events belonging to a swarm activity precursory of the ultimate fracture which formed fracture planes nearly parallel to the loading axis. About two thirds of the events in the group-I show dilatational P-wave first motions at almost all the observation points. The focal mechanism of these events is considered as a sudden closure of pore. On the other hand, almost all the events in the group-II show quadrantial distributions of P-wave first motions which can be reasonably assigned to the double couple sources. The predominant orientations of their two nodal planes are subparallel to the fracture planes and nearly perpendicular to the loading axis. These focal mechanism solutions may suggest that the microfracturings in the swarm region are closely related to the stress-induced tensile cracks whose planes are preferentially oriented parallel to the forthcoming fracture planes.抄録全体を表示PDF形式でダウンロード (965K) -
村上 英記, 山田 功夫, 藤村 彰夫1986 年 39 巻 3 号 p. 361-369
発行日: 1986/09/25
公開日: 2010/03/11
ジャーナル フリーThe geomagnetic total force survey using a proton magnetometer was carried out around the epicenter of the 1984 Western Nagano Prefecture Earthquake (1984. 9. 14, M 6.8) in December 1984 and December 1985. Geomagnetic anomalies ranging from -200 to -500 nanoteslas were observed along the southern boudary of the aftershock region. It is considered that these negative anomalies reflect the crustal structure around the earthquake fault extending to N70°E direction. Obseved anomalies reveal that there is the vertical contact separatig layers of differig magetic susceptibilities at the depth deeper than several ten meters. The magnetic susceptibility of the layer lying south of the contact is 0.002 to 0.005 lager than that of the layer lying north. The vertical contact is 100 to 200 meters thick.
Changes of a few nanoteslas were observed during the period from December 1984 to December 1985. However, further study is necessary to conclude whether these changes were associated with the earthquake because the accuracy of diurnal correction was still not satisfactory.抄録全体を表示PDF形式でダウンロード (1296K) -
山田断層の西方延長地域西村 進, 茂木 透, 赤松 信, 松田 高明1986 年 39 巻 3 号 p. 371-380
発行日: 1986/09/25
公開日: 2010/03/11
ジャーナル フリーGeological, geophysical and hydrogical surveys were carried out in the westward extended area of the Yamada fault. The Yamada fault is well known as a seismic fault occurred at Tango earthquake (March 7, 1927: M 7.5) as well as that of the Go-mura fault. From geological and hydrogical surveys, some remarkable outcrops, topographical evidences and mineral springs which show the existence of the fault were found in the surveyed area, especially Izushi-Cho, Hyogo Prefecture. The hidden fault was traced by gamma-ray and ELF-MT soundings. Gamma-ray intensity was measured at three sites at Izushi-Cho. Resistivity surveys by a ELF-MT method were conducted in the two sites. The spatial distribution of the obtained gamma-ray intensities and apparent resistivities reveals the existence of high intensity and low resistivity belts along the fault which was inferred form the other surveys. These belts have a width more than 1km in a direction of N70-80°E and a width of some hundred meters in a direction of N70°W.
The results of these surveys show that this fault system was followed from the Yamada fault to the west of Izushi-Cho. This fault system bounds this region into two blocks, as Hokutan and Maizuru blocks.抄録全体を表示PDF形式でダウンロード (1425K) -
長谷川 昭, 海野 徳仁, 山本 明, 高木 章雄1986 年 39 巻 3 号 p. 381-395
発行日: 1986/09/25
公開日: 2010/03/11
ジャーナル フリーAn automatic event detection and location system has been developed to process microearthquake data collected by the seismic network of Tohoku University, which covers northeastern Honshu, Japan. The system is composed of three subsystems. The first one (TDE) is a pre-processing system whose main function is event detection. Preliminary hypocenter determination is also made in this pre-processing system. Automatic picking of first arrivals and hypocenter location for events detected by TDE are performed by the second subsystem (RPS). Earthquake hypocenters are located by an iterative method. First, P arrivals are picked and are used to locate the event. Then the system picks S arrivals by using the expected arrival times from the hypocenter already determined from P arrivals. Hypocenter location is made again by using both P and S arrivals. Subsequently arrivals which do not agree with this location or are missed in the first picking are repicked and the event is relocated. This process is repeated until reasonable result is obtained. In the location procedure included is an algorithm which can remove wrong data or can discriminate two or more events occurred at the same time. The third subsystem (BPS) is a batch processing system for checking the results obtained by RPS.
In June 1984 the system was linked with the telemetering network system of Tohoku University, and since then it has been working in real time. Hypocenter parameters determined from the automatic system are compared to those determined by the manual processing system. It is found that more than 90% of the events with magnitude larger than 2.0 located in and around the network by manual processing are well located by the automatic system. Differences between hypocenter locations obtained by the automatic and manual processing systems are mostly within a standard deviation of determined hypocenters. Hypocenter distribution obtained from the automatic system clearly shows double-planed deep seismic zone beneath the network, which demonstrates hypocenter locations by the automatic system are quite reliable.抄録全体を表示PDF形式でダウンロード (1631K) -
小田 仁1986 年 39 巻 3 号 p. 397-404
発行日: 1986/09/25
公開日: 2010/03/11
ジャーナル フリーThe shape distribution of cracks occurring in a uniaxially stressed rock sample was estimated from P-wave velocity data. The rock sample was uniaxially compressed up to a stress level. After the axial stress was released, the P-wave velocity of the sample was measured as a function of hydrostatic pressure. These procedures were cyclically repeated by changing the axial stress level. The velocity data were inverted to obtain the distribution of porosity of cracks with various aspect ratios on an assumption that the crack's shape is spheroidal. For the virgin rock sample, the porosity of crack with large aspect ratios (thick crack) is larger than that with small ones (thin crack). When the rock sample has undergone the higher axial stress, the porosity of thin crack increases, and that of thick crack decreases. Possible interpretations for this result are (1) occurrence of a number of shear cracks, (2) closure of open cracks due to unloading of axial stress, and (3) collapse of thick cracks pre-existing in the virgin rock sample.抄録全体を表示PDF形式でダウンロード (739K) -
大塚 成昭, 大村 誠, 藤森 邦夫, 田中 豊1986 年 39 巻 3 号 p. 405-417
発行日: 1986/09/25
公開日: 2010/03/11
ジャーナル フリーCharacteristic crustal movements related to the earthquake of magnitude 5.6 near the Yamasaki fault, southwestern part of Hyogo Prefecture were observed at three observation stations in the Rokko active faults area. The observation stations were located about 60km southeast of the epicenter. Although these stations appeared a little too far to detect the strain changes caused by the earthquake of magnitude 5.6, the coseismic and post-seismic changes were observed very clearly. The changes corresponding to the aftershock activities were also found on the strain change curves obtained by subtracting the earth tide variations from the original records. Two anomalous changes which started about a week and about two days before the main shock were seen on most of the records of extensometers. However, it is not clear whether these events were the precursory phenomena or the meteorological disturbances. The anomalous tilt changes were not so remarkable as the strain changes in the case of the present earthquake.
It dose not seem that the observed strain changes were immediately caused by the effects of earthquake sources in the uniform and homogeneous elastic medium. It is supposed that they were caused by the amplified effects of tectonic stress changes or of relative movements of the crustal blocks which were triggered by the occurrence of earthquakes. Therefore, in order to detect the slight changes of crustal movements in relation to occurrence of earthquakes, it might be of great advantage to observe them in the vicinity of active faults.抄録全体を表示PDF形式でダウンロード (1364K) -
黒磯 章夫, 伊藤 潔, 梅田 康弘, 飯尾 能久, 村上 寛史1986 年 39 巻 3 号 p. 419-430
発行日: 1986/09/25
公開日: 2010/03/11
ジャーナル フリーFrequency characteristics of the major aftershocks of the Mid-Japan Sea earthquake of May 26, 1983 (M=7.7) have been studied by use of the waveform records of the telemetered stations of the Abuyama Seismological Observatory and those of the temporary station at Fukaura. The major aftershocks during a month from immediately after the main shock are divided into three groups, type H, L and M by their characteristic frequencies. The shocks of type H are characterized by their anomalously high frequencies of 6-9Hz, whereas the shocks of type L, by comparatively low frequencies of 1-3Hz. The shocks of type M have both low and high frequencies and show rather flat velocity spectra of 1-10Hz. The frequency characteristics of the aftershocks are the same as those recorded at Fukaura where the epicentral distances (50-100km) are much shorter than those (630-810km) of the substations of the Abuyama Seismological Observatory. The aftershock area is divided by the frequency characteristics of the after-shocks into three parts which seem to correspond to the rupture characteristics of the main shock which consists of at least two big events. The aftershocks of type M are frequent in the southern part of the aftershock area where the first event of the main shock propagated from south end towards north-northeast and stopped at the northern end, while the aftershocks of type H occurred only at the central part of the aftershock area where the second event of the main shock began. Furthermore, the shocks of type L are frequent in the northern part where the second event propagated with a slower rupture velocity than the first event of the main shock and with a different rupture direction of south-southeast to north-northwest. This suggests that the frequency characteristics of aftershocks closely correlate with the rupture process of the main shock.抄録全体を表示PDF形式でダウンロード (1154K) -
向山 広, 木村 強, 茂木 透1986 年 39 巻 3 号 p. 431-442
発行日: 1986/09/25
公開日: 2010/03/11
ジャーナル フリーThe study using the slope-shaded map and lineament map from Landsat images reveals that the Kinki district consists of several geologic blocks resembling a mosaic. The main lineaments are divided into four patterns by their direction and geological significance: they are N-S, E-W, NE-SW, NW-SE and sometimes cut each other. Some of them show a relatively good agreements with the distribution of active faults and linear distribution of microearthquake epicenters.
Some large lineaments are located in the boundary of geologic blocks. Their distribution patterns seem to indicate that this district has been under an E-W compressive force at least throughout the Quaternary.抄録全体を表示PDF形式でダウンロード (1760K) -
岡野 健之助, 黒磯 章夫1986 年 39 巻 3 号 p. 443-455
発行日: 1986/09/25
公開日: 2010/03/11
ジャーナル フリーThe crustal structure in the northern Kinki district is examined using apparent velocities of P first arrivals from crustal earthquakes. Data used were mainly obtained by the seismic network of the Regional Center for Earthquake Prediction of Kyoto University. It is most characteristic in this study that no sharp discontinuity in the seismic wave velocity is found at the depth of the Conrad discontinuity. This is suggested by the fact that first arrivals from the 1984 Yamasaki Fault earthquake of about 20km depth show an apparent velocity of about 6.45km/s and their plots against epicentral distances do not suggest the head wave propagating along the Conrad discontinuity. Furthermore, it is examined that the Moho discontinuity is about 36km in depth and the Pn wave about 7.8km/s in velocity. A constant velocity near 6.0km/s is feasible for the P wave in the upper crust of a depth range from 4 to 13km in which the most part of crustal earthquakes occur.抄録全体を表示PDF形式でダウンロード (1219K) -
堀 貞喜1986 年 39 巻 3 号 p. 457-468
発行日: 1986/09/25
公開日: 2010/03/11
ジャーナル フリーThe upper mantle earthquake of MJMA=6.1 which occurred beneath the Kanto district on October 4, 1985 was investigated in detail for analyzing its difference from other earthquakes around this event. Most of the upper mantle earthquakes at depths of 60-80km beneath this region has been explained that they are the interplate earthquakes with the thrust type focal mechanisms caused by the subducting motion of the Pacific plate relative to the overriding plate. But the present event was not categorized into such a type of earthquakes; the focal mechanisms of the main- and the aftershocks were the strike slip types rather than the dip slip ones. Redetermination of the hypocenters of the main- and aftershocks by using selected stations and station corrections revealed that the focal are a of the present earthquake was not smoothly connected with other groups of the upper mantle earthquakes. The present event obviously occurred below the upper surface of the Pacific plate. Namely, it is concluded to be an intraplate earthquake. The Pacific plate seems to be Λ-shape structure in the vicinity of the focal area of the M 6.1 event, where the plate is considered to be strongly coupled with the overriding plate. It is likely that the local difference in the subducting rate of the Pacific plate between the northern and southern limbs of the plate caused the intraplate fructure along the hinge plane of the plate. It is suggested that the temporal variation of the pattern of seismic activity around the focal region of the present event is related to an occurrence of the M 6.1 event.抄録全体を表示PDF形式でダウンロード (1190K) -
第七部 Gutenberg-Richter の関係を解釈する大塚 道男1986 年 39 巻 3 号 p. 469-472
発行日: 1986/09/25
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (448K) -
綱川 秀夫, 横山 直樹1986 年 39 巻 3 号 p. 472-474
発行日: 1986/09/25
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (324K) -
尾池 和夫1986 年 39 巻 3 号 p. 475-477
発行日: 1986/09/25
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (263K) -
平田 隆幸1986 年 39 巻 3 号 p. 478-481
発行日: 1986/09/25
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (460K)
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