著者

寺島 敦

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.189-198, 1990

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It gives us one of the fundamental informations for the counterplan of earthquake disaster prevention to survey how inhabitants faced with strong earthquake motions behave differently, in the regions of high and low seismicities. This study is done by questionnaire about the matter mentioned above. The survey region with low seismicity is the area effected by strong motions of the earthquake (May 30, 1984, <i>M</i>: 5.6) which occurred in the southwestern part of Hyogo Prefecture. The surveys in the cases of Ohita earthquake (April 21, 1975, <i>M</i>: 6.4) and Off Miyagi Earthquake (June 12, 1978, <i>M</i>: 7.4) were already done by OMOTE and MITSuNAMI (1976) and OMOTE <i>et</i> <i>al</i>. (1980), for the regions of high seismicities, respectively. The findings of their papers are referred to the present paper to compare their findings with the results of the current questionnaire. The results are as follows: Responding to JMA intensity scale 5, one hundred percents of the inhabitants in the region of low seismicity act involuntarily and instinctively, while onle 10% of those in the region of high seismicity do so. The findings suggest that the inhabitants in the region of low seismicity are apt to cause secondary disasters such as panic, fire and the like, at lower seismic intensity than those in the region of high seismicity.

著者

村松 郁栄

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.30, no.3, pp.317-338, 1977-12-05 (Released:2010-03-11)

参考文献数

8

被引用文献数

2 1

---

Upper boundaries of the strong earthquake motions recorded until now indicate almost constant value of 20-30 kines (cm/see) over the period range from about 1 second to 20 seconds. Accordingly, it may be thought that a velocity seismometer is suitable to observe the strong earthquake motion. Weak ground motions which occur frequently are also valuable to research the properties of strong earthquake motions. Therefore, the author made a velocity type seismograph which can record the earthquake motions of 100 kines to 0.01 kines with high fidelity in the period range from 0.05 seconds to 40 seconds.The main part of this seismograph has a coupled pendulum which was designed by T. MATUZAWA in 1938 and was improved by the author. The whole system of the coupled pendulum is immersed in high viscous silicon oil. The relative displacement of the pendulum is transformed to electric voltage by means of magnetic flux to which a temperature compensating circuit with a thermistor is connected.

著者

村松 郁栄

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.247-256, 1995-08-25 (Released:2010-03-11)

参考文献数

46

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We developed a broadband velocity type strong motion seismometer for near-field observation of large earthquakes. The recording range of the seismometer is from 100cm/s to 5×10-5cm/s in the period range from 0.05s to 600s. The upper limit of the recording range was examined by large displacement tests and strong shock tests. The lower limit was determined by the response to small amplitude sinusoidal calibration current.The seismometer utilizes a coupled pendulum which consists of two pendulums connected each other by flexible crossing wires and is immersed in highly viscous silicon oil. This structure eliminates the cross-coupling error and suppresses the parasitic oscillations during the strong earthquake motions.The effects of oil temperature on the sensitivity of velocity seismometer and the drift of vertical component were studied in detail. They were reduced to a sufficiently small level by means of a simple thermal shield of styrofoam cover. The effect of atmospheric pressure is found to be negligiblly small. The effects of other environmental noises on the seismometer were also examined.

著者

河角 廣

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.6, no.1, pp.32-53, 1934-01-15 (Released:2010-03-09)

参考文献数

48

著者

岸上 冬彦 矢橋 徳太郎

出版者

SEISMOLOGICAL SOCIETY OF JAPAN

雑誌

地震 第1輯 (ISSN:00371114)

巻号頁・発行日

vol.12, no.9, pp.383-393, 1940

著者

武者 金吉

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.7, no.2, pp.63-71, 1935-02-15 (Released:2010-03-09)

参考文献数

25

著者

尾崎 郁子 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.22, no.2, pp.148-150, 1969-08-30 (Released:2010-03-11)

著者

吉岡 敏和 苅谷 愛彦 七山 太 岡田 篤正 竹村 恵二

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.83-97, 1998-07-03 (Released:2010-03-11)

参考文献数

19

被引用文献数

1 1

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The Hanaore fault is a right-lateral strike-slip active fault about 48km long in central Japan. We carried out comprehensive surveys including trench excavations on the Hanaore fault to evaluate the seismic risk of the highly populated area, such as Kyoto City, along this fault. Three trenches were excavated on the fault. On the exposure of the northernmost Tochudani trench, a fault cutting fluvial sediments and humic soil beds appeared. The youngest age of displaced sediments is 460±60 14C yBP, and the sediments covering the fault is 360±60 14C yBP. This faulting event may be correlated to the historical 1662 Kambun earthquake. The southernmost Imadegawa trench was excavated on the road in the urban area of Kyoto City. A thrust fault cutting humic soil with pottery fragments of the Late Jomon period (about 3, 500 years ago) was observed on the trench walls. It was difficult to detect the age of the last faulting event due to lack of younger sediments and artificial modifications of the surficial materials. However, the southern part of the fault might not move during the 1662 earthquake because the damage in this area was much less than in along the northern and middle part of the fault. The historical documents recorded that the land along the Mikata fault which is located at the north of the Hanaore fault was uplifted, and the land along the western shoreline of Lake Biwa where is the east of the Hanaore fault was subsided during the 1662 earthquake. This means that the 1662 earthquake might be a multi-segment event caused by these three faults, the Mikata fault, the northern part of the Hanaore fault, and the faults along the western shoreline of Lake Biwa.

著者

江口 孝雄

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.227-230, 1989-06-24 (Released:2010-03-11)

参考文献数

12

著者

岩崎 貴哉 佐藤 比呂志

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.165-176, 2009-07-31 (Released:2013-11-21)

参考文献数

81

被引用文献数

2 5

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Recent seismic expeditions with controlled sources in Japan provided important constraints on the deformation styles and physical properties of the island arc crust and uppermantle. The crustal structure in the Japanese Islands is characterized by an upper part with a large velocity variation (5.5-6.1 km/s), a middle part with a velocity of 6.2-6.5 km/s overlying a lower part whose velocity is 6.6-7.0 km/s. In many cases, most shallow microearthquakes are concentrated in the upper crust and upper half of middle crust while the lower half of middle crust and lower crust are reflective with very low seismicity. The uppermost mantle is characterized by a low Pn velocity of 7.5-7.9 km/s. Several observations on PmP phase indicate that the Moho is not a sharp boundary with a distinct velocity jump, but forms a transition zone from the upper mantle to the lower crustal materials. A detailed structural section across the NE Japan Arc from intensive onshore-offshore profiling in 1997-1998 revealed crustal deformation associated with the Miocene backarc spreading of the Sea of Japan. The backbone range of this arc shows a pop-up structure formed by inversion tectonics due to the present compressive stress regime. Crustal thinning associated with the backarc spreading is very clear west of this pop-up structure where the crust deduces in thickness from 30 to 25 km. A section across the SW Japan arc elucidated the detailed subduction geometry of the Philippine Sea Plate and inland crustal evolution associated with processes of accretion and magmatic intrusion. The Outer Zone south of the Median Tectonic Line is characterized by northward dipping structures of accretionary complexes, while the lower part of the crust in the Inner Zone is quite reflective, probably modified and homogenized due to the magmatic intrusion at Cretaceous time. Clear structural images obtained for arc-arc collision zones in central Hokkaido and easternmost part of the SW Japan arc provides direct evidence of crustal delamination. The structure in Hokkaido strongly indicates that the delamination of the Kuril forearc occurs at its brittle-ductile transition zone.

著者

瀬野 徹三

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.1-25, 2020-05-10 (Released:2020-05-26)

参考文献数

143

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Subduction off Miyagi and Fukushima prefectures, northern Honshu, has been recognized as having a triple-planed structure of seismicity at the deep thrust zone in the 40-60 km depth range. This triple seismic zone is composed of thrust-type earthquakes, down-dip compressional and down-dip tensional earthquakes from top to bottom. At the time of the 2011 Tohoku-oki earthquake, peculiar phenomena such as radiation of short-period seismic waves and pre- and after- slow slips within the asperities of M7 class earthquakes were observed over this thrust zone west of the 2011 main rupture zone. Further to the south, where the Philippine Sea plate is subducting beneath Kanto, a triple seismic zone has also been recognized particularly under southwest Ibaraki prefecture. The thrust-type earthquakes at the top of the triple seismic zone off northern Honshu and beneath Kanto have been believed to be interplate events representing the relative motion between the overriding and subducting plates. I conclude that the thrust-type earthquakes beneath southwest Ibaraki prefecture are in fact within the crust of the subducting Philippine Sea slab, not at the surface because their slip vectors are different from the relative motion between the subducting and overriding plates. Therefore, there would be an aseismic plate boundary above the seismicity. I also show that the dip angles of the westerly dipping fault planes of the thrust-type earthquakes off Miyagi prefecture are smaller by 6° in average than the dip of the slab surface in this region, except for the six years prior to the Tohoku-oki earthquake, i.e. prior to 2006. Furthermore, the slip vectors coincide with the relative motion between the overriding and subducting plates only during this period. I infer that the topmost earthquakes of the triple seismic zone off Miyagi prefecture prior to 2006 are thus likely to be within the crust of the subducting plate. The slow slips before and after the Tohoku-oki earthquake would have occurred not within the asperities but along the aseismic plate interface, and the short-period seismic waves would have been radiated due to fractures within the crust associated with the overshooting rupture at the time of the Tohoku-oki earthquake. Many of the so-called repeating earthquakes at the topmost surface of the subducting plate would be in fact intra-crustal events within the slab. M9 earthquakes would interact with the triple seismic zone, not only mechanically, but also through fluid migration, because earthquakes in the triple seismic zone involve dehydration reaction. The irregularity of the occurrence of M9 earthquakes might be due to the inhomogeneous distribution of hydrated minerals in the incoming plate. The subduction zones having M9 earthquakes or under Kanto have a collisional character. I propose to term subduction having both a collisional character and a triple seismic zone as “super-subduction”. The relative motion between the plates is accommodated by the deformations of the crust of the subducting slab as a “plate boundary zone”. The viewpoint of “super-subduction” is necessary to understand earthquakes in subduction zones with a collisional character and dehydration reactions in the slab.

著者

西田 究

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.115-121, 2009-07-31 (Released:2013-11-21)

参考文献数

55

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It has long been believed that only large earthquakes excite free oscillations of the solid Earth. In 1998 a few Japanese groups reported existence of Earth’s background free oscillations even on seismically quiet days. The excited modes are almost exclusively fundamental spheroidal modes with amplitudes of about 0.5 nGal (10-11 m/s2), and they fluctuate persistently in little correlation with their neighboring modes. Cumulative effects of many small earthquakes are too small to explain the amplitudes. These features suggest that the background free oscillations are excited persistently by random disturbances globally distributed near the Earth’ surface. The intensities of these modes clearly show annual and semiannual variations with the largest peak in July and a secondary peak in January. The observed amplitudes of some modes are anomalously large relative to the adjacent modes. These are the modes that are theoretically expected to be coupled with the acoustic modes of the atmospheric free oscillations. All of these features suggest that atmospheric disturbance is one of the most likely excitation sources of this phenomenon. Assuming that atmospheric pressure disturbance acting on the Earth’s surface is a primary excitation source, some quantitative comparison has been made between the atmospheric pressure disturbance and Earth’s background free oscillations. Shortly after the discovery, some groups proposed oceanic excitation mechanism. This mechanism is based on two observations; (1) The typical frequency of Earth's background free oscillations of about 0.01 Hz coincides with that of ocean bottom pressure sensors. (2) The excitation sources are dominated in the northern Pacific in winter of the northern hemisphere and in the circum-Antarctic in winter of the southern hemisphere. The source distribution is consistent with oceanic wave height data. Based on these observations oceanic excitation mechanism by ocean infragravity waves through their nonlinear interaction was proposed. However, the proposed mechanisms work efficiently only in shore regions, and hence may not be consistent with the observed spatial extent of the excitation sources, and they cannot explain observed acoustic resonance. At present there is little consensus about the excitation mechanism that can explain all of the observed features. These observations suggest that excitation sources are superposition of oceanic and atmospheric phenomena. The phenomena of background free oscillations should be understood as those in a single system of the atmosphere, ocean and solid Earth.

著者

高野 和友 木股 文昭

出版者

SEISMOLOGICAL SOCIETY OF JAPAN

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.62, no.2+3, pp.85-96, 2009-12-25 (Released:2012-03-26)

参考文献数

44

被引用文献数

1

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This study reexamines the ground deformation and fault slip model of the 1945 Mikawa earthquake (M =6.8), central Japan. We reevaluate two geodetic data sets from the years 1886/1887 and 1955/56 that were obtained from the Geographical Survey Institute; these data sets consist of displacements calculated from the net adjustment of triangulation surveys carried out before and after the Mikawa earthquake. We remove the interseismic deformation and coseismic deformation of the 1944 Tonankai earthquake from the two unique data sets used in our analysis. Maximum coseismic horizontal displacements of over 1.4 m were detected to the west of the Fukozu fault. We estimated the coseismic slip by analyzing our data set. The geometry of the fault planes was adopted from a recent seismicity study and from the surface earthquake fault of this area. The best fit to the data is obtained from two faults along the sections running north and south of the Fukozu and Yokosuka faults. The estimated uniform-slip elastic dislocation model consists of two adjacent planes. The fault also appeared to connect the sections running north and south of the Fukozu and Yokosuka faults. Because it can suitably explain the coseismic deformation due to two earthquake source faults, the earthquake source fault is not admitted under the section for the run. The mechanism is considered to be two reverse faults with right-lateral components. The estimated slips for the two source faults are 2.5 m and 1.4 m, respectively. The pressure axis is directed along NE-SW or E-W. The total seismic moment determined from this model is 1.6 × 1019 Nm, corresponding to Mw=6.7.

著者

松村 正三

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.58, no.1, pp.55-65, 2005-06-10 (Released:2010-03-11)

参考文献数

21

被引用文献数

2 1

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Peculiar seismic activities are occurring beneath Lake Hamana inside the subducted Philippine Sea slab at depths of about 30km. They consist of three spindle-shaped earthquake clusters with NW-SE axes, in a left-stepping alignment in the EW direction, with several kilometers between them. Illustrations of the focal mechanisms indicate that they act like an open crack under NW-SE compression and NE-SW tension and are caused by a right-lateral shear force acting on the Philippine Sea slab. A stress pattern simulation model suggests the following explanation of the situation. A localized locked zone is positioned on the plate boundary just north of the clusters. Separated from the main locked zone, it is considered to be one of the satellite asperities surrounding the main one. The main locked zone is located eastward from Lake Hamana and is expected to become the seismogenic zone of the forthcoming Tokai earthquake. These clusters have demonstrated a remarkable decrease in activity since the second half of the year 2000. An anomalous tectonic movement detected by GPS measurements occurred almost simultaneously. This indicates that a slow slip event progressed on the plate boundary beneath Lake Hamana; that is, the locking must be released there. Since the current change in seismic activity corresponds with this movement, it can be attributed to tectonic stress change due to the slow slip. We estimate that at least three similar periods of quiescence have occurred during the last quarter century. Tidal gauge findings at Maisaka and the crustal tilt at Mikkabi, both of which were observed near Lake Hamana, have indicated almost simultaneous occurrences of similar anomalies. As a result, three episodes of slow slip were identified: the first occurred before 1980, the second around 1990, and the last has been ongoing since late 2000. This implies that the slow slip repeats quasi-periodically with an interval of about one decade. We consider that the locked zone beneath Lake Hamana is a small asperity with a potential of slowly and intermittently slipping due to a weak coupling condition in an area sandwiched between two seismogenic zones of the Tokai and Tonankai megathrust earthquakes.

著者

寺島 敦 大竹 政和 小沢 邦雄

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.28, no.3, pp.239-267, 1975-10-10 (Released:2010-03-11)

参考文献数

10

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Recently, it is suggested that underground water plays an important part in generating the earthquakes. Studies are made in the present paper on changes in flow rate, temperature and heat capacity of hot springs distributed in southern Izu peninsula. These changes are considered to be related closely with the change of underground water caused by the Izu-Hanto-Oki (off the Izu peninsula, Japan) Earthquake (138°48′E, 34°34′N, h: 10km, M=6.9, May 9, 1974).Both of the flow rate and temperature of these hot springs were found to be increased just after the earthquake.Increases of flow rate and heat capacity discharged in the Shimogamo spa contiguous to the epicentral area began about 5.7 years before the earthquake. This abnormality reverted just before the earthquake. This period of about 5.7 years fit the period of precursory phenomena prior to the occurrence of the earthquake M=6.9 expected by “Dilatancy Model”. Moreover, the behavior of the variation bears a close resemblance to what is expected for the behavior of underground water as precursory phenomena prior to earthquakes by “Dilatancy Model”.

著者

大見 士朗

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.68, no.1, pp.1-15, 2015-05-15 (Released:2015-07-07)

参考文献数

19

被引用文献数

2

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Seismic activity near Mt. Hotaka in the Hida Mountains, central Japan was analyzed by using the Matched Filter Method (MFM). In this analysis, MFM was implemented as an automatic hypocenter relocation system. We selected about 30 template earthquakes in the target region that enables us to detect more than 3,000 events and locate about 800 earthquakes in the time period from April 2013 to October 2013. Comparison with manually inspected results indicates that location errors by MFM system is within a couple of kilometers. The seismic activity in the target region started in April 2013 and most intense activity occurred in October 2013. The largest event took place on October 8, 2013 at 19:28 (JST) whose magnitude was 3.9 (JMA). Epicentral area extends about 4km in EW direction with 1km in NS direction at the eastern frank of Mt. Hotaka. Although manually inspected catalogue data is essential to evaluate seismic activity, we suppose MFM is one of the powerful tools to automatically obtain preliminary results for the swarm activity that concentrated in a small area such like this study or volcanic regions.

著者

齊藤 竜彦

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.93-101, 2009-07-31 (Released:2013-11-21)

参考文献数

58

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This paper deals with the stochastic scattering theory for short-period seismic waves in random media. The stochastic approaches to simulate the seismic wave propagation in the heterogeneous lithosphere was employed by K. Aki in seismology in 1970s. His pioneering studies proved that stochastic approaches are very useful for understanding short-period seismic wavefield which is usually too complicated to simulate by deterministic approaches. Numerous researches have since employed stochastic methods to study short-period seismograms. H. Sato and his colleagues have greatly contributed to the development of the scattering theory. Analyses of seismograms based on the theory have revealed that the random inhomogeneity in the lithosphere is well characterized by a power-law spectrum, with the regional variation related to seismotectonic conditions. Recent observations and advanced data analyses, however, are requiring more development of the scattering theory to simulate seismic wave propagation not only in isotropic random media but also in anisotropic random media. This paper covers multiple-forward scattering theories for velocity shift and seismogram envelopes. The achievement of the scattering theory in isotropic random media and the recent progress in anisotropic random media are reported.

著者

岸上 冬彦 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.11, no.8, pp.365-371, 1939-08-25 (Released:2010-03-09)

参考文献数

5

著者

小田切 聡子 島崎 邦彦

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.47-61, 2001-07-15 (Released:2010-03-11)

参考文献数

79

被引用文献数

2

著者

樋渡 康子 佐藤 魂夫 今村 文彦

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.4, pp.431-440, 2002-04-25 (Released:2010-03-09)

参考文献数

15

被引用文献数

1

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Three earthquakes and accompanying tsunamis of 1704, 1793 and 1804 hit the coastal area of the Aomori-Akita districts in the northern part of Japan Sea, causing several hundreds of fatalities and serious damages to houses and ships. In this study, we simulate the generation and the propagation of these tsunamis by assuming several fault models, and determine a set of fault parameters for each earthquake that best fits the observed distributions of tsunami heights and crustal uplifts. The fault model previously proposed by Sato (1980) for the 1704 Iwadate earthquake generally explains the observed tsunami heights, but a similar model with the fault length 3km longer towards the north is more consistent with the reported crustal uplift at Henashi peninsula. For the 1793 Ajigasawa earthquake, a fault model lying off the coast of Tsugaru peninsula better explains the observed tsunami heights around Ajigasawa. The tsunami simulation also corroborates the observation that tsunami caused by the event might flush into the Jyusan Lake. Among several fault models tested for the 1804 Kisakata earthquake, a fault model located most offshore shows the best agreement with the observed distribution of tsunami heights. The tsunami simulations for the 1704 Iwadate and 1804 Kisakata earthquakes show that the tsunamis are largely amplified at Oga peninsula. The amplification is ascribed to an energy concentration by the reflection in the 1704 Iwadate tsunami and the edge wave trapped in the shallow sea in the 1804 Kisakata tsunami, respectively. Both are important mechanisms affecting the heights of tsunamis along the Japan Sea coast.