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 4

---

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

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

---

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

---

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

---

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

---

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

---

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)

著者

石橋 克彦 佐竹 健治

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.1-21, 1998-03-31 (Released:2010-11-17)

参考文献数

164

被引用文献数

34

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We review long-term forecasts of great earthquakes along subduction zones around Japan and discuss the related problems from a paleoseismological point of view. Rich historical data in Japan show the recurrence of great earthquakes along subduction zones, particularly at the Nankai trough, for more than 1, 000 years. On the basis of such historical data and interseismic/coseismic vertical crustal movements, Imamura made a rather vague forecast of great earthquakes along the Nankai trough as early as 1933, which turned out to be successful by the occurrence of the 1944 Tonankai (Mw 8.1) and 1946 Nankai (Mw 8.1) earthquakes. After plate tectonics theory was established, the concept of seismic gap in subduction zones has been thought as a powerful tool for long-term earthquake forecasts. Great interplate earthquakes have been predicted from examinations of not only seismic gaps but also other observations such as seismic quiescence, earthquake recurrence history, current crustal deformation in coastal areas, or seismic crustal movements in geologic records. The 1973 Nemuro-oki earthquake (Mw 7.8) along the Kurile trench was predicted in 1972, although it was slightly smaller than the predicted size. The 1978 Miyagi-oki earthquake (Mw 7.6) along the Japan trench was also predicted in 1977, although the size and place were somewhat different from the prediction. The Tokai earthquake was predicted in 1976, and its occurrence has been considered imminent. Despite that short-term surveillance system has been in operation in the last 20 years, this earthquake has not occurred yet. In 1994, two great/large earthquakes occurred in subduction zones off northeast Japan, but no forecasts had been made on these. The off-Hokkaido event (Mw 8.2), whose aftershock area apparently coincides with that of the 1969 interplate earthquake (Mw 8.2), has been interpreted as an intraplate event within the subducted Pacific slab. The Sanriku-oki earthquake (Mw 7.7) was aninterplate event, but its rupture zone overlapped with a previous interplate event, the 1968 Tokachi-oki earthquake (Mw 8.2). The recurrence history of interplate earthquakes along the Nankai trough has been updated by seismo-archaeologlcal data such as liquefaction evidence at archaeoiogical sites. and it now seems more regular and can be explained by time-predictable model. In the mean time. historical data indicate that the 1605 earthquake was an unusual “tsunami earthquake” and the source process is very different from the other repeated events. This event may have been affected by a preceding large inland earthquake in 1596. Paleoseismological investigation is still very important for long-term forecast of earthquakes. Future research should emphasize to complement recurrence history of interplate earthquakes from historical as well as seismo-archaeological data, to distinguish intraplate (slab) earthquakes from interplate earthquakes in historical catalog, to investigate the co-relation between interplate and inland earthquakes, and to combine historical, geologic and other kinds of data to study earthquake recurrence as demonstrated in the Cascadia subduction zone.

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.43, no.2, pp.227-232, 1990-06-24 (Released:2010-03-11)

参考文献数

17

被引用文献数

5 5

---

It is reported by an old document that the Yamagata-Oki earthquake of Dec. 7, 1833 (Oct. 26, Tenpo 4), hitting the Yamagata, Niigata and Akita districts destroyed 475 houses in the Shonai plain and the tsunami killed about 150 persons. In this paper the distributions of the seismic intensity and the tsunami behavior along the Japan Sea coast are investigated with an addition of newly collected data. The magnitudes of earthquake and tsunami are compared with those of the 1964 Niigata and the 1983 Japan Sea earthquakes. The results are summarized as follows:1) According to the intensity-distance diagram, the earthquake, magnitude is inferred as M=7.5, because the same intensity area is smaller than that of the 1983 Japan Sea earthquake and similar to that of the 1964 Niigata earthquake.2) By judging from the tsunami height-distance diagram (HATORI, 1986), tsunami magnitude on the Imamura-Iida scale is m=2.5, which are somewhat larger than the former value. Extraordinary run-up heights at Wajima (tip of Noto peninsula) and Oki Islands located in far field may be caused by the refractive effect and the reflected waves from the continental coasts.

著者

武村 雅之

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.4, pp.377-396, 1998-03-13 (Released:2010-03-11)

参考文献数

28

被引用文献数

2

---

Strong ground motion in Tokyo metropolis during the Sep. 1, 1923 Kanto earthquake was important factor for determining the seismic design code in Japan. However, it has not been clarified in detail, because of no strong motion record near the source region of the Kanto earthquake. The author collected the descriptions and made a data set of 548 personal experiences in and around the southern Kanto district to investigate the strong ground motion from the Kanto earthquake. Many descriptions in Tokyo metropolis indicated that three severely strong shakings arrived at this area during the Kanto earthquake. The first shaking was, of course, caused by the main shock (M=7.9) at 11:58AM (JST). The second and the third shakings were caused by the aftershocks occurring 3 minutes and 4.5 minutes after the main shock, respectively. These aftershocks were identified on a seismogram obtained at Gifu observatory and magnitudes of them were determined to be 7.2 and 7.3, respectively from this seismogram [TAKEMURA (1994)]. The results of the analyses of the personal experiences also indicated that the duration time of the first shaking due to the main shock was 30 to 40sec. The strength of the second shaking was as strong as the first shaking, of which seismic intensity was estimated to be VI in JMA scale, while duration time of the second shaking was shorter than the first shaking. On the other hand, the third shaking was weaker than the first and the second shakings, of which seismic intensity was estimated to be V. The sequence of strong shakings within 5 minutes after the occurrence of the main shock of the 1923 Kanto earthquake was elucidated in Tokyo metropolis in the present study.