著者

瀬野 徹三

出版者

SEISMOLOGICAL SOCIETY OF JAPAN

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.64, no.2, pp.97-116, 2012-01-25 (Released:2012-02-20)

参考文献数

83

被引用文献数

13 23

---

Great earthquakes have historically occurred along the Nankai Trough. It has been said that they ruptured part or whole of characteristic fault planes A, B, C, D, and E repeatedly. However, there are a number of enigmas for their occurrence. Major ones are as follows. The 1944 Showa-Tonankai earthquake occurred only 90 years after the 1854 Ansei earthquakes. The 90-year period seems short compared with other time intervals of the historical earthquakes. The Tonankai earthquake did not rupture fault plane E west of the Suruga Trough, by some unknown reasons. The Tokai earthquake anticipated at fault plane E has not occurred yet since the Ansei-Tokai event even if a slow slip event occurred recently near the downdip end of its rupture zone. In this study, I propose a model to solve these enigmas. I characterize a fault plane of a great earthquake into a seismic-b.eq, a tsunami-b.eq, and a geodetic-b.eq, in which seismic waves, tsunamis, and crustal deformations are dominantly generated, respectively. I compare these different bands of rupture zones between the 1944 Showa-Tonankai and 1854 Ansei-Tokai earthquakes, the 1946 Showa-Nankai and 1854 Ansei-Nankai earthquakes, and the 1707 Hoei and other earthquakes, using seismic intensity data and previous studies on asperities, tsunamis, and crustal deformations. It is found that the Ansei-Tokai and Showa-Tonankai earthquakes scarcely shared their seismic-b.eqs. The tsunami- and geodetic-b.eqs of the Ansei-Tokai earthquake extended to the west of its seismic-b.eq, and was shared by, but did not cover the seismic-, tsunami- and geodetic-b.eqs of the Showa-Tonankai earthquake. It cannot thus be said that the Ansei-Tokai earthquake ruptured fault planes C+D+E or that fault plane E was left unbroken after the Showa-Tonankai earthquake. The occurrence of these two earthquakes is rather complementary from a viewpoint of the seismic-b.eq. The seismic-b.eq of the Ansei-Nankai earthquake also seems to have been different from and was located further north than that of the Showa-Nankai earthquake. On the other hand, the Hoei earthquake had a seismic-b.eq similar to those of the Showa earthquakes. I group historical great earthquakes into the Ansei-type or the Hoei-type, which has a seismic-b.eq similar to either of the Ansei or Hoei earthquake. It is likely that the Ansei-type earthquakes are the 684 Hakuho, 1096 Eicho-1099 Kowa, 1498 Meio, and 1854 Ansei earthquakes and recurred with a ∼400-year period, and that the Hoei-type earthquakes are the 887 Ninna, 1361 Shohei, 1707 Hoei, and 1944 Tonankai-1946 Nankai earthquakes and recurred with a ∼350-year period. Since the Showa-Tonankai earthquake was complementary to the Ansei-Tokai earthquake, the 90-year period between the two events is not a recurrence time and it is natural that the Showa-Tonankai did not rupture fault plane E. It is also natural that the next Tokai earthquake did not occur even if the slow slip event occurred at its downdip end, because it is expected to occur at least ∼200 years after present, because the earthquake precedent the Ansei-Tokai event would be the 1498 Meio earthquake.

著者

松浦 律子

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.65, no.1, pp.1-7, 2012-09-28 (Released:2012-10-26)

参考文献数

17

被引用文献数

6

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There are several European historical materials on Tensho Earthquake, which occurred on Jan. 18, 1586 in the south-western part of Chubu district. The through research of those materials revealed that all the information of Tensho earthquake was originated from letters written by L. Frois in October 1586 at Shimonoseki Port, Yamaguchi Prefecture as the annual report of missionary in Japan. Since a letter was hand-copied, edited, and translated to Italian or Latin from Portuguese in the late 16th century, there derived some versions of descriptions on damage of the earthquake. The letter in the Portuguese version published in Evora, Portugal in 1589, and the remained copies of the manuscript of "Japanese History" by Frois are only two reliable sources. From those credible European materials, it is apparent that there was the common talk in Kyoto after Tensho earthquake of Tsunami damage along the northwestern coast of Japan. However, it is no more than a rumor.

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, 1954-09-05 (Released:2010-03-11)

著者

岡村 行信

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.185-199, 2019-03-10 (Released:2019-04-09)

参考文献数

87

被引用文献数

2 5

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An active fault map of Japan Sea was compiled based mainly on bathymetric data and seismic profiles that cover shelves to slopes between 4 to 150 km from the coasts of Japan Islands. The seismic profiles using air guns as seismic sources revealed active faults that have slipped during the last 104 to 106 years. In addition, high-resolution seismic profiles using a boomer as the seismic source were obtained along seaward extensions of onshore active faults in shallow sea areas less than 150 m below sea-level, and activity of the faults during the last 104 years was identified. In northeastern Japan Sea, to the northeast of the Noto Peninsula, many reverse faults accompanying large hanging wall anticlines (>750 m uplift) are concentrated in two N-S trending fault zones along the Okushiri and Sado ridges. Earthquakes larger than M 7.5 in 1940, 1964, 1983 and 1993 occurred in these fault belts. Three NE-SW trending fault zones cross the N-S trending fault zones and disrupt the structure of the N-S fault zones. In the offshore area from the Noto Peninsula to the Tango Peninsula, active reverse faults accompanying smaller hanging anticlines (<375 m uplift) are identified in a zone trending subparallel to the coasts. In addition, NW-SE to N-S trending strike-slip and reverse faults extend from onshore to offshore. In the offshore area to the west of the Tango Peninsula, E-W and NW-SE trending active strike-slip faults are identified. The former faults developed in about 40 km wide zones sub-parallel to the coast, and the later faults are located landward of the E-W trending fault zones. Some of the later faults are extensions of onshore active faults. Unknown active faults may exist in shallow sea area along coasts where have not been thoroughly investigated. Displacements of the faults during the last 106 years are large in northeastern Japan Sea and decrease to the southwest, while slip rates of these faults during the last 104 years are inferred to have smaller differences. These faults have the potential of future earthquakes, while there is not enough data to evaluate the activities of these faults.

著者

加納 靖之

出版者

日本地震学会

雑誌

地震. 2輯 (ISSN:00371114)

巻号頁・発行日

vol.69, pp.41-47, 2016

著者

阿部 邦昭 岡田 正実

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.46, no.1, pp.25-34, 1993-06-24 (Released:2010-03-11)

参考文献数

9

被引用文献数

1 1

---

We succeeded in explaining a small tsunami on a vertical displacement field of a pure strike-slip fault. The Izu-Oshima Kinkai Earthquake (M=6.5) of February 20, 1990, being accompanied with a small tsunami, was modeled as a pure strike-slip fault on a focal mechanism solution and aftershock area. The sinistral strike slip fault with a plane of 15×12km2, dip of almost 90° and strike of N0°E was assumed at the epicenter.A numerical experiment on the vertical displacement field reproduced the observed tsunami fairly well. The computation was carried out on a linear framework using a mesh of 1km, time step of 1 sec and an additional fine mesh of 0.25km in the vicinity of tide stations. The assumed dislocation of 1m explained the observed amplitude at the nearest tide station. Comparison of waveforms between model and four observations supports the model.Furthermore, a spectral analysis was attempted to reveal predominant frequencies of the observed tsunami. The observed predominant frequencies were explained from wave lengthes characteristic to the pure stlike-slip fault. A strong azimuth dependence is one of the characteristic properties of the pure strike slip tsunami. An unexplainable predominant frequency was attributed to the reflected wave from the Izu Oshima Island.

著者

瀬尾 和大 小林 啓美

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.1, pp.23-36, 1980-03-25 (Released:2010-03-11)

参考文献数

27

被引用文献数

1

---

It has been frequently said that seismograms obtained in Tokyo contain rather long-period components in themselves. Authors pointed out the importance to make clear extensive and deep underground structure of the Tokyo Metropolitan area, based on the experience on simultaneous observation of earthquake ground motions under the different kinds of geological conditions.In this paper, results on the seismic prospectings in the southwestern part of the Tokyo Metropolitan area were presented. Outline of the interface between sedimentary layers and the uppermost layer of the earth's crust was shown in the form of “time-term”, along the line stations from Yumenoshima, Tokyo to Enoshima, Kanagawa. The length of this line was almost 50 kilometers long.From the distribution of those time-terms, it was made clear that the interface mentioned above changes its depth more remarkably and rapidly, in comparison with those which obtained in other parts of the Tokyo Metropolitan area by many researchers. Most of all, Enoshima and its vicinities were confirmed to be situated on the boundary which distinguishes inner sedimentary zone of the Kanto Plain from outer outcrop zone of firm substratum.From these results, the mechanism of formation and propagation concerning rather long-period earthquake ground motions can be expected to be elucidated.

著者

岡田 正実

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.35, no.1, pp.53-64, 1982-03-25 (Released:2010-03-11)

参考文献数

26

被引用文献数

1 3

---

Monthly distribution of major shallow earthquakes (M≥7.5) in and near Japan is investigated using earthquake catalogs including pre-instrumental data. Major shallow earthquakes off Hokkaido and Sanriku districts are concentrated in spring, and those along the coast from Miyagi prefecture through Shikoku district occurred more frequently from August to December, as Mogi has pointed out. We suggest with some consideration that these variations are statistically significant at a 95% confidence level. In the other region the records on major earthquakes are not enough to discuss the seasonal variation. But it is able to show that large earthquakes with magnitude 7.0 or over occurred more frequently from March to September in the inland regions where no effect of the major earthquakes on the Pacific coast is expected. It seems that the decrease in the weight of water on land and lowering of the mean sea level trigger the occurrence of major earthquake between the oceanic and continental plates, when the strain accumulates closely to the limit. It is also considered that the increase of ground water in the fault zone has an influence on the occurrence of large shocks inland in their critical states.

著者

山口 覚 村上 英記 大志万 直人

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.1, pp.17-31, 2001-07-15 (Released:2010-03-11)

参考文献数

11

被引用文献数

1

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Many types of luminous phenomena were observed at the 1995 Hyogo-ken Nanbu earthquake (Kobe earthquake) of January 17, 1995. A questionnaire survey was done regarding luminous phenomena in order to determine 1) spatial distribution of eyewitnesses of luminous phenomena; 2) origin-times and duration-times of the phenomena; 3) properties of lights, such as color, shape, and brightness.Out of 798 people surveyed, 31 answerers (3.9% of the total) reported that they had observed luminous phenomena. Characteristics of the phenomena may be described as follows; a) More than 50% of the eyewitnesses were within 10km of the epicenter of the main shock. b) Almost all observations of the phenomena occurred simultaneously, or at a maximum of 2-3 minutes from the arrival of the seismic wave to the eyewitnesses' location. c) The duration-time of the phenomena was less than 30 seconds. d) The gross form of luminescence was a belt of light or curtain shape. e) The colors of luminescence were white, blue, and orange, while blue-white was predominant.

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.32, no.3, pp.355-359, 1979-09-25 (Released:2010-03-11)

参考文献数

9

著者

宇津 徳治 関 彰

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.4, pp.233-240, 1955-03-30 (Released:2010-03-11)

参考文献数

28

被引用文献数

6 33

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The after-shock regions of 39 shallow earthquakes which took place in and near Japan (Table 1) are determined and the relation between thier areas and the magnitudes or energies of main-shocks is investigated. If we assume that the logarithm of the area A (km2) and the magnitude M are in linear relation, i. e., logA=aM+b (Fig. 2-3), the constants a and b become as follows, a=1.02±0.08, b=-4.01±0.57 (for 39 total earthquakes)a=0.93±0.08, b=-3.18±0.61 (for 23 oceanic earthuakes)a=0.85±0.10, b=-3.05±0.72. (for 16 land earthquakes)From the relation between M and E (erg), we get A∝Em, where m≈1/2, then E/A∝A∝√E, this means that the surface density of energy increases as the energy increases.

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.29, no.4, pp.355-363, 1976-12-15 (Released:2010-03-11)

参考文献数

5

被引用文献数

2 2

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The Kalapana tsunami was generated off the south coast of Hawaii Island, accompanying the earthquake of magnitude Ms=7.2 (NOAA), at 14h 48m (GMT), Nov. 29, 1975. Some features of this tsunami are investigated on the basis of tide gauge records of NOAA and Japan, adding the reports of the US field investigation.Tsunami magnitude of the Imamura-Iida scale is decided as m=2, judging from the tsunami heights observed near and distant fields. The initial motion of the tsunami waves was in an upward direction at the whole Hawaiian stations, suggesting the uplift of the sea-bottom in the tsunami source area. The source dimension of tsunami is inferred to be 70km along the south coast of Hawaii Island, and the area is 2.2×103km2. By applying the corrections for the refraction and shoaling from the inundation heights at the Hawaii Island, the average vertical displacement of 1.2m would be occurred in the source area. The tsunami energy of approximately is 1.6×1020 ergs. According to statistical relation, the present tsunami is large compared with the earthquake magnitude.The tsunami fronts arrived in NE Japan at about 7h 40m after the occurrence of the earthquake. The maximum double amplitude is 20-30cm with the period of about 15min and the amplitude is relatively higher than that in SW Japan. It is noticed that the wave rays emitting the tsunami source concentrate in the Kuril Islands.

著者

ゲラー ロバート

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.appendix, pp.309-312, 1998-03-31 (Released:2010-11-17)

参考文献数

37

著者

今村 明恒

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.8, no.7, pp.347-352_2, 1936-07-15 (Released:2010-03-09)

著者

粟田 泰夫 杉山 雄一

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.42, no.2, pp.231-233, 1989-06-24 (Released:2010-03-11)

参考文献数

19

被引用文献数

4

著者

泊 次郎

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.66, no.1, pp.11-14, 2013-06-26 (Released:2013-10-01)

参考文献数

8

著者

松村 稔 伊藤 喜宏 木村 尚紀 小原 一成 関口 渉次 堀 貞喜 笠原 敬司

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.59, no.2, pp.167-184, 2006-12-15 (Released:2013-08-05)

参考文献数

27

被引用文献数

7 10

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We have developed an automatic system called the Accurate and QUick Analysis System for source parameters (AQUA System) that provides rapid estimates of hypocenter location, magnitude, and moment tensor for medium to large-scale earthquakes that occur near or underneath Japan. The AQUA System monitors high-sensitive real-time seismic waveform output from the Hi-net operated by the National Research Institute for Earth Science and Disaster Prevention (NIED). Upon detecting an earthquake, the AQUA System provides an estimate of the event’s hypocenter and magnitude within 15-30 seconds. Within a further 2-10 minutes, the system provides centroid moment tensor (CMT) solution by inversion technique using broadband seismic waveform of NIED F-net. To assess the accuracy of the new system, we compared hypocenter and magnitude data derived from the AQUA System over the period from September 2004 to August 2005 with catalog data from the Japan Meteorological Agency (JMA). We also compared CMT solutions derived from the AQUA System with corresponding values from the NIED F-net and catalog data of Harvard University’s CMT Project. A total of 339 seismic events were detected during the period of analysis. The AQUA System determined hypocenters for 324 of these events and CMT solutions for 224 events. The estimated hypocenters are within 10km horizontally and 20km vertically of the hypocenters calculated by the JMA in 80% of cases, and the CMT solutions were approximately the same as those obtained from other systems. The results of analyses by the AQUA System are published on the website of NIED Hi-net.

著者

山中 浩明 瀬尾 和大 佐間野 隆憲 翠川 三郎 嶋 悦三 柳沢 馬住

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.4, pp.527-539, 1988-12-25 (Released:2010-03-11)

参考文献数

17

被引用文献数

6 6

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Seismic waves from explosions at nine sites were observed at a number of temporary stations in the southwestern Kanto plain. Travel time analyses were carried out along the several surveying lines, so that the contradiction at cross points of the lines becomes as small as possible. Underground structures along the surveying lines were studied to reveal the three dimensional features of the region. The results are summarized as follows:1) The structure consists of four layers which have P-wave velocities of 1.8, 2.8, 4.8 and 5.5km/s, respectively. Around the Yumenoshima explosion site, however, the thickness of the 4.8km/s layer seems to be very thin.2) The depth to the 4.8km/s layer becomes largest around Yokohama as more than 4km. The thickness of this layer is more than 3km in the central part of the area considered, such as Okazu and Hiratsuka. However, it becomes shallower near the Kurokawa and Higashi-ohgishima explosion sites.3) A step-like structure was found on the top of the 5.5km/s layer at points along the several surveying lines in the southeastern extension of the Tachikawa fault toward the Tokyo Bay area. On the southwestern side of the step-like structure, the depth to the 5.5km/s layer is more than several kilometers and this layer exists near the ground surface of the Kanto Mountains.

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.23, no.4, pp.335-336, 1970-12-28 (Released:2010-03-11)

著者

湯村 哲男

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.22, no.3, pp.253-255, 1969-11-30 (Released:2011-03-08)