著者

小笠原 宏 川方 裕則 石井 紘 中谷 正生 矢部 康男 飯尾 能久 南アフリカ金鉱山における半制御地震発生実験国際共同研究グループ

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.563-573, 2009-07-31 (Released:2013-11-21)

参考文献数

54

被引用文献数

2 3

---

Experimental sites with potential earthquakes up to M ∼ 3 in coming few years are known beforehand from mining schedule at 2-3 km depths in South African gold mines, which allows us to deploy various borehole instruments including Ishii strainmeters, geophones, accelerometers and AE sensors. Deployment of these wide-dynamic-range and high-resolution observations in the past 15 years has led to many findings about the earthquake rupture and its preparation stage. High-sampling seismograms obtained at close proximity of M > 1 earthquakes have demonstrated similarities of these earthquakes to natural, greater earthquakes in many aspects, including stress drop, energy efficiency, and complexity of rupture propagation. Some of larger mine earthquakes are preceded by perceivable abnormal seismicity. However, no immediate precursors for earthquakes with M ∼ 2 were observed by our high-resolution strain and AE sensors installed within the dimension of mainshock rupture. In contrast, aseismic strain-step events that we had recently discovered were sometimes preceded by further slower forerunners. Ongoing projects bring in novel technologies such as field-scale AE monitoring and fast-response strainmeters, and novel targets including mines being flooded for closing operation.

著者

橋本 学 多田 堯

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.41, no.1, pp.29-38, 1988-03-25 (Released:2010-03-11)

参考文献数

22

被引用文献数

4 4

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Displacements and strains during the recent 80 years in Hokkaido are investigated by the analysis of triangulation or trilateration data. According to the distribution of displacements and strains, Hokkaido can be separated into three blocks, eastern, middle and southwestern Hokkaido.In eastern Hokkaido, northwestward displacements and NW-SE contractions are dominant before the 1973 Nemuro-Oki earthquake, while seaward displacements and EW extensions are detected after the event. Summing up them, westward displacements are left, which suggests westward sliding of the outer Kurile arc along the volcanic front and colliding at the Obihiro Tectonic Line [TADA and KIMURA (1987)].The Ishikari Low Land, which is considered to be a relic trench, may be the boundary between middle and southwestern Hokkaido along which E-W contractions are prevailing. This observation suggests that northern Honshu would not belong to the North American or the Okhotsk plate.Displacements associated with four major earthquakes which occurred during the period between the first and the last surveys are computed. Results show that the 1940 Shakotan-Oki earthquake may not give much influence on Hokkaido. Theoretical displacements computed by models for the 1952 Tokachi-Oki (M8.1) and 1968 Tokachi-Oki (M7.9) earthquakes are inconsistent with the observation, which may require re-analyses of data. The model for the 1973 Nemuro-Oki earthquake can predict the observed displacements qualitatively. The observed displacements are greater than the computed ones by a factor of two or three, which means that old triangulation surveys might suffer from scale errors.

著者

多田 堯

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.29, no.1, pp.47-53, 1976-03-10 (Released:2010-03-11)

参考文献数

10

被引用文献数

1 1

---

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.

著者

加藤 昭七郎

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.10, no.3-4, pp.123-140, 1957-12-25 (Released:2010-03-11)

参考文献数

10

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Assuming the fluid motion of vT1°-type (expression (3.1) in §3), we have studied here the time characteristics of self-exciting fluid dynamos. As a result of theoretical calculations, it has been found that three magnetic fields expressed by three surface spherical harmonics Ymn-1, Ymn and Ymn+1((n, m)-harmonics in §3) can coexist independently of other magnetic fields. These three magnetic fields oscillate concurrently in intensity quasi-periodically with time, the frequency being proportional to order m, fluid velocity and depth of the fluid layer. The westward drift of the earth's magnetic field and also the reversal of the magnetic field of the sun may be well explained by the above results. The periodical dynamo presented here may also be appropriate as a model for magnetic variable stars.

著者

熊谷 博之 中野 優

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.379-390, 2009-07-31 (Released:2013-11-21)

参考文献数

85

被引用文献数

1

---

We review recent advances in quantification of the sources of volcano-seismic signals. Since the 1990s, there have been remarkable advances in quantitative understanding of the sources of volcano-seismic signals. These were made by integrated contributions from observation, analysis, and modeling studies in volcano seismology. We focus on the following topics in this review paper: Broadband seismic observations on active volcanoes, waveform inversions of volcano-seismic signals, and source models based on resonances of a fluid-filled crack, bubble dynamics, and repeated fracture and healing of magma. Broadband seismic observations revealed the general existence of very-long-period seismic signals with oscillation periods longer than a few seconds beneath active volcanoes. Development of waveform inversion methods enabled us to estimate source mechanisms of volcano-seismic signals, which indicate that crack geometry is the most common in volcano-seismic sources. Source models have been successfully used to interpret dynamic interactions between volcanic fluids and the surrounding solid rock. Quantitative studies of volcano seismology are now reaching a mature stage, and links with geological and geochemical studies will be important future directions to achieve a better understanding of magmatic and hydrothermal processes beneath active volcanoes.

著者

茂木 清夫

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.3, pp.263-264, 1972-12-30 (Released:2010-03-11)

参考文献数

6

著者

渡辺 偉夫

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.48, no.2, pp.271-280, 1995-08-25 (Released:2010-03-11)

参考文献数

14

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Previous equation for the tsunami-magnitude scale after Abe (1981) has been re-examined using a more general form: M10=logA+a log Δ+b, where Mto is tsunami magnitude, A is the maximum double amplitude of tsunami as recorded on a tide gage, Δ is the shortest distance along oceanic path from the earthquake epicenter to a tide station, and a and b are constants. ABE (1981) used a=1 and b=5.55 in his determination of tsunami magnitude. This paper demonstrates, using more extensive sets of tide records, that the constants, a and b, vary regionally. For instance, a=0.86 and b=5.96 for tsunamis along the Pacific coasts in and around Japan, and a=0.52 and b=6.56 for tsunamis in the Japan Sea. These constants vary even in more regional scales and may depend on the submarine topography along a tsunami path. Renewed equations should be used for the determination of tsunami magnitude.

著者

渡辺 偉夫

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.50, no.1, pp.29-36, 1997-05-28 (Released:2010-03-11)

参考文献数

20

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A method for judging tsunami earthquake is proposed. The method uses a simple formula for calculating the judging factor α from JMA seismic intensity and epicentral distance. α corresponds to the difference between the tsunami magnitude by WATANABE (1995) Mto and JMA earthquake magnitude MJ. [WATANABE (1994)]We apply this method to some recent and some historical tsunamigenic earthquakes around the Japan Islands. The results are as follows.1) Among 19 tsunami earthquakes, eight earthquakes have α values of 0.6 or more and one has α value of 0.5.2) The criterion α≥0.6 is suitable for identifying tsunami earthquake, because number of tsunami earthquakes of α≥0.6 is almost the same as the number of earthquakes of Mto-MJ≥0.6.3) Historical earthquakes of 1605, 1611 and 1677 were tsunami earthquakes. However, the earthquake of 1793 had a normal tsunami.4) Tsunami earthquakes around the Japan Islands are distributed along the Japan trench, off the southeast coast of Hokkaido and along the Nankai trough. It must be noticed that two tsunami earthquakes of 1611 and 1896 occurred off the Sanriku coast, and the two tsunami earthquakes occurred simultaneously in 1605 off the Kii peninsula and the Tokai coast.

著者

出射 隆文 堀家 正則 岩田 知孝

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.38, no.2, pp.217-232, 1985-06-25 (Released:2010-03-11)

参考文献数

18

被引用文献数

1 2

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We have investigated the characteristics of S coda waves on a sedimentary basin for examining if they may be applicable to estimate the stable amplification factor. The results are as follows: (1) R. M. S. amplitude ratios of coda waves observed on the basin to coda waves on the nearest rock site were inconsistednt with the ratios of S waves between the above two sites for frequecies lower than 3Hz. The ratios of coda waves scattered as much as those of S waves. (2) The phase velocities determined for coda waves on the basin were consistent with those of Rayleigh waves estimated by another study. (3) Comparing coda waves observed on the basin with those synthesized through convolving the SH wave response for the basin and the seismogram on the rock site, the former was much smaller than the latter. From the above three results, coda waves on the basin seem to consist of not only single-scattering S waves but also surface waves generated locally. It is therefore difficult to estimate reliable amplification factor from coda waves observed on the sedimentary basin.

著者

津村 建四朗

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.20, no.1, pp.30-40, 1967-06-25 (Released:2010-03-11)

参考文献数

3

被引用文献数

3 4

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Empirical formulas for the determination of the earthquake magnitude M from the duration of oscillation F-P have been derived from the observational data obtained by the Wakayama Micro-earthquake Observatory, Earthquake Research Institute.The instruments used by the Observatory and its substations are the short period vertical seismographs of the same characteristics (T1=1.0sec, T2=0.025sec, velocity sensibility=40-120uμ kine/mm at 1 to 10c/s).The formula obtained from the comparison of the F-P (sec) observed by the network with the M determined by the Japan Meteorological Agency is:M=-2.53+2.85log(F-P)+0.0014Δwhere Δ is the epicentral distance in km. This formula is applicable to the earthquakes with Δ<1000km and focal depth ≤60km.Since the coethclent for Δ is very small, the correction term of Δ can be neglected for the earthquakes with Δ<200km, and in this case the following simpler formula is more conveniently applied:M=-2.36+2.85log(F-P).The magnitudes obtained by the former and the latter formulas are designated, in the figures and table, MF-P and M′F-P respectively.The largest merits of this method are:1) Wide range of magnitude can be covered with a single seismograph, since there is no difficulty in reading F-P such as ‘saturation’ or ‘under exposure’ in the case of maximum amplitude.2) The treatment is very simple, especially for the earthquakes of short epicentral distances.

著者

羽鳥 徳太郎

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.37, no.1, pp.23-29, 1984-03-25 (Released:2010-03-11)

参考文献数

10

被引用文献数

1 1

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By applying the Greens's law, the sea-level disturbance at the source area of the Nihonkai-Chubu tsunami (May 26, 1983) is calculated from the coastal inundation heights. By means of the same method, the volumes of the displaced water at the source area, V0, for 18 tsunamis are calculated, where the tsunami source area and the shoaling and refraction factors of the coastal heights are analyzed on the inverse and refraction diagrams, respectively. It is found that V0 is closely related to seismic moment, M0.1) For the 1983 Nihonkai-Chubu tsunami, the height of the sea-level disturbance averaged over the tsunami source area is estimated to be 123cm, and the peak of 202cm seems to have disturbed in the southern part of the source area. The volume of the displaced water V0 is 12.3×1015cm3.2) The relation between V0 and tsunami magnitude (Imamura-Iida scale, m) is expressed aslogV0=0.6m+14.7, where the unit of V0 is ×1015cm3. Combining V0 and the seismic moment M0 (dyne-cm), which is empirically expressed aslogV0=0.78logM0-6.23.However, the V0 values for the 1896 Sanriku and 1946 Aleutian tsunamis such as “tsunami earthquake” and the Japan Sea tsunamis (the 1940 Shakotan, 1964 Niigata and the present tsunamis) generated by the high angle fault are three times larger then those of the obtained from the above equation.

著者

加藤 護 日岡 惇

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.68, no.6, pp.151-161, 2016-03-10 (Released:2016-05-19)

参考文献数

34

---

Stone lanterns in temples and shrines often collapse and suffer damages when these sites are hit by a strong seismic ground motion. There have been several reports in Japan that large numbers of stone lanterns collapse in the direction of strong shaking at large earthquakes. Descriptions that stone lanterns were damaged by strong earthquakes frequently appear in historic Japanese documents. In this report, we examine whether it is possible to retrieve characteristics of historic ground motions from the ages and damages of stone lanterns at Kitano-Tenmangu Shrine and Iwashimizu-Hachimangu Shrine, Kyoto. We assume that if ground motions cause severe damages to stone lanterns, they would be removed from the site and be newly rebuilt thereafter, and occurrence of such events would be imprinted on the age distribution of stone lanterns. If the damages are minor, the damaged parts would be reused when stone lanterns are rebuilt at the site, and the damages of stone lanterns we find today could be used as records of occurrence of historical strong seismic ground motions and the direction of collapses. Scarcity of stone lanterns which were built before 17th century at Iwashimizu-Hachimangu Shrine as well as their increase at Kitano-Tenmangu Shrine in mid 19th century are likely results of strong earthquake and resultant damages at these sites. Ratios between numbers of damaged and undamaged stone lanterns at two sites vary with respect to their ages but they do not correlate with records of historic earthquakes in Kyoto. Damages of stone lanterns we observe today appear to distribute evenly with respect to the cardinal directions, whereas these damages are more often found in the rear of the stone lanterns. While the damages we find today could include those due to the historic earthquakes, stone lanterns at these sites are likely to be so maintained that damaged parts are rotated into the direction which makes the major damages less visible. We conclude that it is very difficult to estimate direction of historic strong motion at these sites from the statistics of damages of stone lanterns which we observe today.

著者

堀 貞喜

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.39, no.3, pp.457-468, 1986-09-25 (Released:2010-03-11)

参考文献数

10

被引用文献数

5 5

---

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.

著者

佐藤 泰夫

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.6, no.1, pp.13-35, 1953-08-30 (Released:2010-03-11)

参考文献数

190

著者

羽鳥 徳太郎

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.40, no.1, pp.1-6, 1987-03-25 (Released:2010-03-11)

参考文献数

13

被引用文献数

1

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Based on tide-gauge records, the Hyuganada tsunami of Aug. 7, 1984 is investigated. Adding the present data, the pattern of tsunami activity off the east coast of Kyushu since 1899 is discussed on a space-time diagram. The magnitude (Imamura-Iida scale) of the 1984 tsunami is estimated to be m=-1. This grade is small for an earthquake having magnitude of M=7.1. The source area of tsunami estimated by means of an inverse refraction diagram agrees with the aftershock area, and the source length is 25km in the N-S direction. The initial motion of the tsunami was in an upward direction at Hyuga-Shirahama, but at Tosa-Shimizu and Muroto, the initial disturbance began with a down motion. It suggests the west side of the sea-bottom uplifted and the east side subsided.According to the geographic distribution of the source area of the Hyuganada tsunamis generated during the last 86 years (1899-1984), the tsunami sources are parallel to the bathymetric line and their region is divided by three groups: A) is located near the Kyushu coast, B) about 50km east from the Kyushu coast and C) off the Shikoku coast. A tsunami of each group was generated on extension of the major axis of the former source. Tsunami magnitudes (Imamura-Iida scale, m=0-1.5) of the A and C groups are larger than that of the B group. From the pattern of generating cycle, the northern part of the A group is considered a region of relatively high tsunami risk as a type of the 1941 earthquake.

著者

馬塲 久紀 中尾 凪佐 西宮 隆仁 篠原 雅尚 阿部 信太郎 鶴我 佳代子

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.73, pp.197-207, 2021-01-05 (Released:2021-03-30)

参考文献数

23

被引用文献数

1

著者

宇佐美 龍夫

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.34, pp.1-36, 1981

被引用文献数

1

著者

濱松 音藏

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, pp.73-92, 1981

被引用文献数

2

著者

池上 良平

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, pp.37-72, 1981

被引用文献数

1

著者

羽鳥 徳太郎

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.48, no.1, pp.91-97, 1995-05-25 (Released:2010-03-11)

参考文献数

8

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Accompanied with the Guam earthquake on Aug. 8, 1993 (epicenter: 13.0°N, 144.7°E, d=61km, Ms=8.0, USGS), a tsunami was observed at many tidal stations in Japan. Tsunami magnitude and the behavior of propagation are investigated, comparing with those of the 1990 Saipan tsunami (m=2). The travel times in West Japan were about 3.5 hours. The maximum double amplitude at Muroto and Tosa-Shimizu near the tip of peninsula reached 84cm with the wave-period of 8 minutes, and those in the Ryukyu Islands were relatively small. The distribution pattan of wave-heights is similar to that of the 1990 Saipan tsunami. By judging from the diagram of the attenuation of wave-height with distance, the tsunami magnitude on the Imamura-Iida scale was determined to be m=2.5. Although wave-heights of the present tsunami are about 1.5 times higher than those of the 1990 Saipan tsunami, the magnitude value is normal compared to earthquake with similar size in other regions.