著者

三雲 健

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.1, pp.47-62, 2011-08-25 (Released:2011-10-18)

参考文献数

129

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This report reviews various studies on atmospheric pressure waves that have been generated from large earthquakes, tsunamis, and large-scale volcanic eruptions. These waves described here include low-frequency acoustic and gravity waves (0.0008∼0.0166 Hz or its period 1∼20 min) and high to medium frequency (› 0.0166 Hz or its period ‹ 1 min) infrasonic air-waves. The low-frequency acoustic-gravity waves came from coseismic vertical ground deformation associated with two megathrust earthquakes, and sometimes from other large earthquakes and volcanic eruptions, which propagated to more than several thousand kilometers through the lower to part of the upper atmosphere. The waves that reached the upper atmosphere could cause traveling ionospheric disturbances and perturbations of total electron content. The higher frequency infrasounds also have often been observed after large earthquakes and volcanic eruptions, which traveled as air-waves propagating directly from the source, and also as air-waves coupled with traveling seismic Rayleigh waves. Small atmospheric perturbations have also been detected during propagation of tsunami waves caused secondarily by large submarine earthquakes. Theoretical waveform modeling has been made in some of the above cases, incorporating a realistic atmospheric temperature structure. It is expected that more detailed information about the source process of large earthquakes and volcanic eruptions could be extracted through the analysis of the waveforms recorded at a number of stations, including their maximum amplitudes, wave frequencies, duration times, directions of wave approach, and phase and group velocities.

著者

三雲 健

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.99, no.1, pp.18-31, 1990-02-25 (Released:2010-11-18)

参考文献数

58

被引用文献数

3 4

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Extensive studies on seismic activity and focal mechanism of major to moderate-size earthquakes that occurred along the eastern margin of the Japan Sea and the northern part of the Fossa Magna regions are reviewed and discussed in relation to regional tectonics. The validity of a prevailing hypothesis is also tested from various observations to see if the Northeast Honshu arc is part of the North American plate.Seismicity along the Japan Sea coastal regions extends southwestwards across the Toyama trough in one way, and also in other way to the northern Fossa Magna through a zone near the Shinano river. It has been noticed that the seismicity show temporarily successive properties similar to migration phenomena. Five major earthquakes along the Japan Sea regions have been interpreted as having thrust-type mechanisms, and the depth distribution of aftershocks of two larger events and the dip of submarine active faults suggest an eastward dipping fault plane.The maximum compressive stress derived from the focal mechanisms of more moderatesize earthquakes indicates E-W to ESE-WNW orientations, changing gradually from the northern to southwestern part of the coastal regions. In inland regions west of the northern Fossa Magna, the general trend appears oriented again in the ESE-WNW direction, which is found to be well consistent with the direction of principal compressive strains derived from geodetic triangulation surveys over the last 80 years.All the above evidence suggests that the regions under consideration may be a tectonically active, convergent zone, and might be regarded as a zone of a possible plate boundary. There is no direct evidence, however, suggesting an eastward incipient subduction of the Japan Sea lithospheric plate, from observations of submarine topography and upper crustal structure beneath the regions.Numerical calculations show that the suggested hypothesis could partly account for the observed directions of compressive stress in Northeast Honshu but is apparently inconsistent with those in Southwest Honshu. The results suggest that the Northeast Honshu arc may better be regarded as a “micro-plate” which receives strong compressive stress not only from the westward movement of the Pacific plate but also from the west side. One of possible sources of the driving stress from the west side might be an eastward movement of the “Amurian plate” which is one of micro-plates detached from the Eurasian plate. Another possible source could be bilateral extension of the central Japan Sea region or of the regions covering Northeast China and the Korean peninsula.

著者

三雲 健 大塚 道男 尾池 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.23, no.3, pp.213-225, 1970-09-28 (Released:2010-03-11)

参考文献数

17

被引用文献数

1

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The focal mechanism of 20 microearthquakes in the Wakayama region have been determined from the seismograms recorded at ten temporary stations and eight routine network stations covering the region.The hypocenters of the earthquakes have been determined for five different crustal models (with a continuously varied velocity profile), to estimate the accuracy of their location and the emergent angle of seismic rays at the focus. The radiation pattern of P wave first motions for the 15 shocks, which was corrected for an appropriate crustal structure, can be interpreted by the double-couple type mechanism with dipping nodal planes.The average of the maximum pressure axes is oriented nearly horizontally along the N70°W-S70°E direction, while the axes of the maximum tension show a steep dip in many cases. If a slip dislocation is assumed to be a likely model of the earthquakes, the source would be thrust faulting with a predominant component of dip slip. The other five earthquakes shows, however, the radiation pattern inconsistent with the double-couple type mechanism.

著者

尾池 和夫 三雲 健

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.1, pp.54-66, 1968-05-30 (Released:2010-03-11)

参考文献数

6

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A multipartite seismometer array with a span of about 1km has been set up at one of the temporary stations for the observation of microearthquakes in Wakayama region, to examine the effects of local underground structure.The apparent velocity and direction of wave approach for about 200 microearthquakes were determined by means of least squares from arrival times of P waves at 5 recording sites, as well as from the conventional tripartite technique. Parameters computed from 4 selected tripartite nets show systematic deviations from the results of least squares in relation to the azimuth. A possible explanation for the azimuthal dependence and for average travel-time residuals for each of the recording sites would be that there exists an upward-warping interface in the shallow portion of the crust. Several kinds of later phases can be identified on seismograms between the initial P and S waves. Their apparent velocities and travel-times appear to be consistent with the interpretation that these phases may be SV waves converted from incident P waves or vice versa at the above interface.

著者

三雲 健

出版者

京大地球物理の歴史を記録する会

雑誌

京大地球物理学研究の百年(II)

巻号頁・発行日

vol.2, pp.45-54, 2010-10-25

著者

和田 博夫 三雲 健 小泉 誠

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.281-296, 1979-09-25 (Released:2010-03-11)

参考文献数

28

被引用文献数

2 3

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Seismicity in the northern Hida region, Japan, has been routinely observed since May, 1977 at telemeter-network stations of the Kamitakara Geophysical Observatory, and about 1500 local shocks with magnitudes greater than 0.5 have been located. (1) The observation reveals high seismicity along the Atotsugawa fault, along the northern Japan-Alps, south of Mt. Norikura and Mt. Ontake, and near Hida-Osaka, with focal depths shallower than 20km. (2) Seismic activity along the Atotsugawa fault is high at the eastern and western portions, with an intermittent zone of low activity, extending over 70km. Epicenters are deviated about 2-3km north of the fault trace, and this deviation together with focal depth distribution suggests a slightly northwestwardd dipping fault plane. All these shocks are confined above 13km, suggesting either that the fault plane extends down to this depth, or that minor brittle fractures do not take place under the depth due to some flow propertities of rock materials there. (3) Nine shocks along the fault show focal mechanisms consistent with right-lateral strike-slip evidenced by geological and geomorphological surveys (MATSUDA, 1966). (4) Heavy damage along the fault region at the time of the 1858 Hida earthquake (M=6.9) appears to indicate that this large earthquake was caused by faulting motion of the Atotsugawa fault. Most of the present seismic activity along the fault might be associated with some readjustments of residual stresses around there.

著者

三雲 健

出版者

日本自然災害学会

雑誌

自然災害科学 (ISSN:02866021)

巻号頁・発行日

vol.22, no.1, pp.49-57, 2003-05-30

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A large earthquake (Mw7.4) occurred on January 22, 2003 off the Pacific coast of the state of Colima, Mexico, which was felt strongly throughout the state and its adjacent regions. The hypocenter was located near the suggested boundary between the Rivera and Cocos plates both subducting beneath the North American plate, and close to the southeastern rim of the source region of the 1995 Colima-Jalisco earthquake (Mw8.O). From a centroid moment tensor (CMT) inversion of teleseismic waveforms, the 2003 earthquake has been shown to have a thrust fault shallowly dipping toward NNE. The ruptured source region estimated from the aftershock area with a radius of about 30 km extended over part of the seismic gap left unbroken between the source areas of the 1973 and 1995 previous large earthquakes, and overlapped the southeastern part of the 1932 and 1995 source regions. The earthquake has been recorded at various seismograph stations not only in Mexico but also worldwide. The maximum ground acceleration recorded at hard sites during this earthquake exceeded 100 gals in the epicentral region, and was 2-3 gals at inland stations 800 km away from the epicenter. The seismic intensity in the cities of Colima and Tecoman was reported to be VIII on the modified Mercali scale. The state of Colima and the adjacent states suffered extensive damage, including 15,000 damaged houses which were mostly unreinforced masonry and brick structures. Landslides and liquefactions were also reported near the epicentral region and along the coast.