著者

多田 堯 飯田 汲事

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.25, no.4, pp.295-301, 1973-03-30 (Released:2010-03-11)

参考文献数

13

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The relationships between the predominant period and the magnitude of the microearthquakes were studied. We assume the relationship in the following form. LogT=a+bM where, T is the predominant period in second and M is the earthquake magnitude. The following results were obtained, LogT=-1.50+0.50M (P wave, microearthquakes occurred in the vicinity of the Neo-Valley) LogT=-1.12+0.45M (S wave, microearthquakes occurred in the vicinity of the Neo-Valley) LogT=-1.38+0.44M (P wave, microearthquakes occurred in the vicinity of the Inuyama City) LogT=-2.03+0.65M (P wave, Matsushiro earthquake swarm) LogT=-1.45+0.40M (whole P wave). From the dislocation theory, the relation of T and M is derived as follows, LogT=-0.3-0.7 Logσ+0.5M. (1) where, σ is the stress drop in bar. Substituting σ=40 bars into (1), we get LogT=-1.4+0.5M. (2) This equation agrees well with the above mentioned results. But, when σ is not constant, the equation (1) suggests that the difference of the predominant period in the same earthquake magnitude is the differences of the stress drop. Indeed, the deviations of the data are so large that the stress drops seem to be not constant.The predominant periods of the Matsushiro earthquake swarm are shoter than those of the other microearthquakes. This evidence may relate to the characteristics of the Matsushiro earthquake swarm.

著者

飯田 汲事 坂部 和夫

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.25, no.1, pp.44-55, 1972-07-30 (Released:2010-03-09)

参考文献数

8

被引用文献数

3

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The western extension of the Fuk6zu fault associated with the Mikawa earthquake in 1945 was investigated by the present geological survey. It was ascertained that the extension of the fault has begun near the pass between the villages, Kiriyama and Miyabasama and has been followed as far as Shikoyamachi, Nishio city, a total distance of about 9km. As the result of this survey a total length of the earthquake fault formed by the Mikawa earthquake in 1945 became about 28km as shown in Fig. 3. The fault is of a reverse type, and it has manifested itself as a northeastward upthrusting of the land on the southwest side of the fault amounting up to about 1.8m.The fault also may presumably continue to the northwest and further to the Nobi earthquake fault which was formed in 1891, based on the seismological standpoint. It is concluded that a number of destructive earthquakes in the past might occur in connection with a chain of faults such as the Fukui, the Nobi, and the Mikawa earthquake fault.

著者

飯田 汲事

出版者

公益社団法人 日本地震学会

雑誌

地震 第1輯 (ISSN:00371114)

巻号頁・発行日

vol.13, no.3, pp.67-74, 1941-03-25 (Released:2010-11-17)

参考文献数

13

著者

正木 和明 坪井 利弘 飯田 汲事

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.34, no.1, pp.135-144, 1981-03-25 (Released:2010-03-11)

参考文献数

10

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Shear wave velocity, soil density and standard penetration test value in depth at 35 boring points in Nagoya area were measured by means of P and S wave-velocity logging up to about 100m in depth. The empirical equations for estimating shear wave velocity and soil density were derived on the basis of these underground data as well as soil characteristics. By making use of these equations and boring data (depth, standard penetration test value, soil age and soil facies), shear wave velocity and soil density in depth were estimated. By means of multi-reflection method of shear wave, transfer functions at about 280 mesh points in Nagoya area were calculated, and distributions of maximum amplification factors and predominant periods were obtained. It was found that maximum amplification factors were large and predominant periods were long in the western part of Nagoya area. The relation between the maximum amplification factor, and the damage ratio in the Nobi and the Tonankai Earthquakes was studied, and it was clarified that the larger maximum amplification factor the greater damage ratio bacame.

著者

永井 理子 菊地 正幸 山中 佳子

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.54, no.2, pp.267-280, 2001-09-20 (Released:2010-03-11)

参考文献数

25

被引用文献数

29 54

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In an attempt to examine the characteristic behavior of fault asperities (large slip areas), we comparatively studied two large earthquakes: the Tokachi-oki earthquake (M 7.9) of May 16, 1968 and the Sanriku-oki earthquake (M 7.5) of December 28, 1994, which have a partially common source area. Both the strong motion records at a regional network and the teleseismic body waves at global networks were analyzed to determine the detailed spatio-temporal distribution of moment release. The aftershock distribution, which may provide us with a more reliable location of asperity, was also re-examined using the same underground structure and the same algorithm for both events.The total seismic moment, Mo, and the source duration, T are obtained as: Mo=3.5×1021Nm; T=90s for the 1968 event, and Mo=4.4×1020Nm; T=60s for the 1994 event. It is also shown that the 1968 event consists of more than two asperities, one of which took a role of asperity again for the 1994 event. The distribution of relocated aftershocks, which fringe the major asperities, strongly supports this fact. A simple calculation indicates that the seismic coupling is almost perfect (100%) in this common asperity. We thus propose that there exist characteristic sites for asperities where fault slip occurs only as a seismic event, and that the individual asperities usually manifest M 7 class earthquakes but sometimes synchronize to cause M 8 class earthquakes.

著者

遠山 忠昭 檀原 毅 里村 幹夫

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.37, no.4, pp.539-547, 1984-12-25 (Released:2010-03-11)

参考文献数

4

被引用文献数

1 1

---

Although γ-ray surveys have often been carried out in order to research active faults, clear correspondence of γ-ray intensity to faults has not always been obtained. We examined over again the methods of γ-ray surveys and the following two points came up as important problems.(a) The hole to set the senser of γ-ray survey meter must be bored in the same radius and depth at each survey point.(b) Much attention must be payed to the difference of surface materials.In order to confirm the usefulness of the method in which the above two points are taken into consideration, the γ-ray surveys were carried out along a line across the Himenoyu fault. This fault was formed at the time of North-Izu earthquake in 1930, and its traces are yet clearly found. A clear peak of γ-ray intensity was obtained at the position on the fault.Next, this method was applied to the Ono fault whose precise position has not yet known, and we estimated the position of the fault by the results of γ-ray surveys.

著者

荒井 克彦 小嶋 啓介

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.52, no.1, pp.219-227, 1999

著者

神田 茂

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.21, no.2, pp.141-142, 1968-08-30 (Released:2010-03-11)

著者

宮本 貞夫

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.7, no.2, pp.136-137, 1954

著者

佐藤 裕

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.33, no.3, pp.395-397, 1980-09-25 (Released:2010-03-11)

参考文献数

3

著者

平松 良浩 小阪 大

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.65, no.3, pp.251-254, 2013-01-31 (Released:2013-07-19)

参考文献数

11

被引用文献数

1

著者

渡辺 晃

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.26, no.2, pp.107-117, 1973-10-30 (Released:2010-03-11)

参考文献数

5

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Frequency distribution of magnitude of the ultramicro-earthquakes was studied by using the data of the Matsushiro earthquake swarm observed in December 1966.As a result of analyses, the Gutenberg-Richter's formula concerning the frequency distribution of magnitude was found to hold well for the magnitude range down to about -0.9. The number of shocks then decreased very sharply with decreasing magnitude and no shocks of magnitude less than -1.3 were registered, though still within the limit of detection capability of the sensors. The seismograms of smaller events, if any, should be identified as earthquake motions, because the signal to noise ratio for a minimum shock was yet about 3, so that smaller events could not be masked by disturbances.A crude estimation showed that the linear dimension of the focal region for the minimum shock was of the order of a couple of meters. The size of focus for the shock of magnitude -0.85, where a peak in the frequency distribution occurred, amounted roughly to double the size for the minimum one.

著者

森重 学

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.71, pp.1-11, 2018-05-10 (Released:2018-06-26)

参考文献数

82

被引用文献数

1 1

著者

山内 常生 山田 守 奥田 隆

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.34, no.3, pp.301-310, 1981-10-25 (Released:2010-03-11)

参考文献数

16

被引用文献数

1 1

---

Precursory abnormal strain responses associated with rainfall are discussed in the present paper. The data analized are the strains observed at the Mikawa Crustal Movement Observatory (Toyohashi City, central Japan) for the period from January 1973 to April 1980. Each extensometer at the observatory is equipped with two or three sensors for the detection of irregularity in strain. Usually the observation gallery deforms uniformly after a rainfall, because the ground strain responses observed by the sensors attached on the same quartz pipe show nearly the same variation. We can calculate accurately these strain responses by a tank model from the precipitation at the observatory, but sometimes remarkable disagreements between the ground strains caused by rainfalls and the calculated values expected from the model are clearly seen before and after the occurrence of nearby earthquakes. Irregular deformations at the observation site are also observed. These abnormal strain responses to rainfall are observed for 18 earthquakes during the period from January 1973 to December 1979. Distribution of earthquakes which were accompanied by these precursory abnormal strain responses are restricted in the block whose boundary is characterized by the distribution of microearthquakes.

著者

佐藤 春夫 立川 真理子 大久保 正

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.37, no.2, pp.197-205, 1984-06-25 (Released:2010-03-11)

参考文献数

15

被引用文献数

2 2

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Preceding the eastern Yamanashi earthquake of magnitude 6.0, an anomalous tilt change up to 0.4 micro-radian was detected by the borehole-type tiltmeter at the Enzan station locating 31km north-west of the epicenter. The anomaly began 18 days preceding the earthquake and continued 10 days. The tiltmeter was installed at the bottom of the well of 89m depth. The resolution is 0.006μ radian and the long-term stability is better than a few μ radian per year. This tiltmeter had recorded similar tilt changes of the order of 0.4μ radian twice since it was installed in 1979. Both the changes had been caused by a large amount of precipitation accompanied by typhoons. During these 10 days, however, the maximum daily precipitation was 20mm, temperature change was smaller than 0.05°C at the bottom of the well, and there was no construction near the station. Therefore, we may interpret this anomalous tilt change as a precursor of the earthquake. The station is located in the fracture zone associated with the active fault, the Daibosatsurei-nishigawa fault; core samples obtained from the well were fractured and their P wave velocity was extremely low. The direction of the anomalous tilt vector change is nearly orthogonal to the strike of this active fault. This suggests that the observed upheaval of the epicentral block is the consequence of the hinge movement at the fault.

著者

岡田 真介 小松原 琢 中澤 努 中村 洋介 坂田 健太郎 納谷 友規

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.64, no.4, pp.257-264, 2012-06-25 (Released:2012-08-08)

参考文献数

11

被引用文献数

1 1

著者

渡辺 晃

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.24, no.3, pp.189-200, 1971 (Released:2010-03-11)

参考文献数

12

被引用文献数

22 46

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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.

著者

中島 淳一 長谷川 昭

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.61, no.Supplement, pp.177-186, 2009-07-31 (Released:2013-11-21)

参考文献数

65

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Since late 1990’s, a dense nationwide seismograph network has been constructed in the Japanese Islands with an average station separation of ∼ 20 km, which has produced the highest quality data in the world and contributed to enhance the understanding of seismotectonics and volcanotectonics there. Travel-time tomography using such high-quality data has provided two important constraints on water-transportation paths in subduction zones. One is the evidence for hydrous minerals in and immediately above the slab. The hydrated oceanic crust is imaged as a low-velocity layer to a depth of 40 km for the Philippine Sea slab and 70-130 km for the Pacific slab. Another low-velocity layer is revealed immediately above the Pacific slab down to a depth of ∼ 110 km, which might correspond to a hydrous layer through which water is carried to deeper depths. The other is seismological imaging of mantle upwelling. Mantle return flows induced by the subduction of the Pacific and Philippine Sea slabs are imaged in Tohoku and Kyushu, respectively, whereas that probably generated by the subduction of both the Pacific and Philippine Sea slabs is apparent in central Japan. A large upwelling in the upper mantle revealed in the Chugoku district might be the origin of Quaternary volcanism there.

著者

岩田 貴樹 中西 一郎

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.51, no.1, pp.51-59, 1998-07-03 (Released:2010-03-11)

参考文献数

29

被引用文献数

1

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We investigate the correlation between the occurrence of earthquake and the earth tide by analyzing the tail of the Matsushiro earthquake swarm that is recorded by the Matsushiro Seismic Array System during the period of November 1984 to December 1994. The seismic activity of the tail exhibits many bursts of earthquakes. We remove the bursts, because they affect our aim to investigate whether the correlation exists or not. We use the tidal strain data recorded by EW- and NS-component extensometers located in Matsushiro Seismological Observatory, Japan Meteorological Agency. We apply Schuster's test to the Matsushiro earthquake swarm. The hypothesis that the earthquakes in the swarm take place randomly is tested and is rejected for the EW-component. The earthquakes tend to occur when the tidal strain of the EW-component is in a compressional state. This state is consistent with the stress field at Matsushiro obtained by using focal mechanisms or in situ stress measurements.We also investigate the spatial variation of the correlation. A significant correlation is seen in the northwestern part of Matsushiro. The largest earthquake with magnitude of 5.2 occurred on 30 December 1986 near the region. We further investigate the temporal variation of the correlation in this region. The correlation becomes high right after the occurrence of the largest earthquake, whereas the correlation is low before the occurrence of it. This suggests that the strain changes caused by the largest earthquake make the correlation high in this region.

著者

久保寺 章

出版者

日本地震学会

雑誌

地震 (ISSN:00371114)

巻号頁・発行日

vol.13, no.4, 1960-12