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

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

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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

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

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

内田 直希 松澤 暢 三浦 哲 平原 聡 長谷川 昭

出版者

SEISMOLOGICAL SOCIETY OF JAPAN

雑誌

地震. 2輯 (ISSN:00371114)

巻号頁・発行日

vol.59, no.4, pp.287-295, 2007-03-25

参考文献数

26

被引用文献数

5 4

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Spatio-temporal distribution of quasi-static slip on the plate boundary east off Miyagi and Fukushima prefectures, NE Honshu, Japan is estimated by using small repeating earthquake data. The analysis of small repeating earthquakes has advantages of relatively high spatial resolution, especially near the trench, and the availability of long-term data (22 years) compared to GPS data. The results show that the repeating earthquakes are distributed outside the coseismic slip areas (asperities) of large earthquakes, showing that fault creep is dominant outside the asperities. The cumulative slip (slip histories) of small repeating earthquake groups reveal the existence of many non-steady aseismic slip events. Most of the episodic quasi-static slip events are associated with <I>M</I>≥ 6 earthquakes and they are frequently seen in the areas near the Japan trench in particular. Minor afterslip (∼15cm) of the 2005 Miyagi-oki earthquake (<I>M</I>7.2) is also estimated in the area which encompasses the coseismic slip area of the 2005 earthquake.

著者

水野 真理子 佐藤 利典 篠原 雅尚 望月 公廣 山田 知朗 金澤 敏彦

出版者

SEISMOLOGICAL SOCIETY OF JAPAN

雑誌

地震 第1輯 (ISSN:00371114)

巻号頁・発行日

vol.62, no.1, pp.19-23, 2009

被引用文献数

2

著者

竹本 修三 MORI James RIVERA Luis FRECHET Julien

出版者

SEISMOLOGICAL SOCIETY OF JAPAN

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.63, no.1, pp.45-55, 2010-06-15 (Released:2012-03-26)

参考文献数

21

著者

功刀 卓 青井 真 中村 洋光 藤原 広行 森川 信之

出版者

SEISMOLOGICAL SOCIETY OF JAPAN

雑誌

地震 第1輯 (ISSN:00371114)

巻号頁・発行日

vol.60, no.4, pp.243-252, 2008

被引用文献数

20

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A new calculation method is proposed for a real-time seismic intensity indicator (<i>I</i>_r), whose concept is similarly to the JMA seismic intensity (<i>I</i>_JMA)defined by Japan Meteorological Agency. With the increasing requirements of earthquake early warning (EEW) system, it is much more obvious that <i>I</i>_JMA has a real-time delay since the <i>I</i>_JMA needs a filtering operation in frequency domain. In order to improve the real-time calculation suitable for the EEW system, a new real-time seismic intensity indicator, <i>I</i>_r (real-time seismic intensity), is defined by using an approximating filter in time domain instead of the original filter in frequency domain. This indicator, <i>I</i>_r,can be calculated as a time series on real-time and its maximum value, <i>I</i>_a (approximate seismic intensity), corresponds to an approximate value of <i>I</i>_JMA. The relationships between <i>I</i>_JMA and <i>I</i>_a value are examined by means of using a large number of strong motion records. Results show that <i>I</i>_a value estimates <i>I</i>_JMA with reasonable accuracy in wide intensity ranges. For a small computing system like a strong-motion seismograph, it is easier to process <i>I</i>_r than processing <i>I</i>_JMA. Therefore, <i>I</i>_r is suitable for using in an EEW system based on the concept of JMA seismic intensity.

著者

溜渕 功史 山田 安之 石垣 祐三 高木 康伸 中村 雅基 前田 憲二 岡田 正実

出版者

SEISMOLOGICAL SOCIETY OF JAPAN

雑誌

地震 第1輯 (ISSN:00371114)

巻号頁・発行日

vol.62, no.4, pp.193-207, 2010

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We found eight <I>M</I> 5.1 characteristic earthquakes regularly occurring since 1966 on the plate boundary between the Eurasian plate and the Philippine Sea plate near Miyakojima Island, the Ryukyu Arc, Japan. The quake recurrence interval was 5.89 years in average, and the standard deviation was only 0.73 years. The accumulating stress presumably ruptured the same asperity enclosed by the creeping zone repeatedly. Also, we found three other groups of small repeating earthquakes of <I>M</I> 4, which occurred close to the hypocenters of the <I>M</I> 5 events. Those groups also occurred regularly and we can consider them to be 'characteristic' earthquake sequences. Now, we called those groups A, B, and C. It is not clear whether groups A and B had an intrinsic recurrence interval or if they influenced each other. However, two events of group C occurred within one week after the <I>M</I> 5 quakes, indicating that the <I>M</I> 5 events triggered the group C events whose asperity had suffcient strain energy. No earthquake exceeding <I>M</I> 7, which could change the recurrence intervals, has been observed on the subduction zone around the Ryukyu Islands. Therefore, there should be numerous characteristic earthquake sequences in other areas of the Ryukyu district. We expect that the next <I>M</I> 5 earthquake at 50 km depth on the plate boundary near Miyakojima Island will occur between September 2012 and July 2014 with 70% probability, using the small-sample theory with a log-normal distribution model. Moreover, the <I>M</I> 5 event may be accompanied by an <I>M</I> 4 quake that could rupture the asperity of group C within one week.

著者

藤原 広行

出版者

SEISMOLOGICAL SOCIETY OF JAPAN

雑誌

地震 第1輯 (ISSN:00371114)

巻号頁・発行日

vol.66, no.4, pp.67-71, 2014

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There is a similarity between the distribution of prime numbers and the pattern of earthquake occurrence. Earthquakes occur in a discrete manner in time and space. When viewed as a whole, however, we find some laws, such as Gutenberg-Richter law, that govern the entire earthquakes that seem to be individually independent. A similar phenomenon can be observed also in the world of number. The most basic example is the distribution of the prime numbers in integers. We consider a correspondence between earthquakes and prime numbers. We parameterize occurrence time of earthquakes as the prime numbers and magnitude of earthquakes as the interval of prime numbers. Then we obtain a relationship similar to Gutenberg-Richter law. We call the model obtained by this correspondence as "arithmetic seismic activity model". If we can parameterize earthquakes using prime numbers, knowledge that has been cultivated in the number theory can be used for understanding of earthquakes. The distribution of prime numbers is related to the distribution of zeros of Riemann zeta function. Researches are in progress to understand the zeros of the Riemann zeta function as an eigenvalue problem of quantum dynamical system. Earthquake may be modeled as a phenomenon corresponding to a change in the energy level of a quantum dynamical system associated with prime numbers.

著者

Kaoru TANIGUCHI Mitsuhisa WATANABE Yasuhiro SUZUKI Hiroshi SAWA

出版者

SEISMOLOGICAL SOCIETY OF JAPAN

雑誌

Zisin (Journal of the Seismological Society of Japan. 2nd ser.) (ISSN:00371114)

巻号頁・発行日

vol.64, no.1, pp.11-21, 2011-08-25 (Released:2011-10-18)

参考文献数

28

被引用文献数

1 2

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The 150 km long Itoigawa-Shizuoka Tectonic Line Active Fault System (ISTL) in central Japan is one of the most active fault systems in Japan. Paleoseismologcal studies 1980s have revealed that the most recent event and the average recurence interval of the ISTL. The approximately 7 km long portion of the fault system between Matsumoto and Okaya has been regarded as a gap without any active fault trace. The gap namely the “Shiojiri Pass Gap” has long been taken as a segment boundary owing to the geometric discontinuity. Recent geomorphological analyses of the gap have demonstrated a through-going left-lateral slip assocaited with recent earthquakes in this area, based on aerial photograph interpretation and excavation studies. Excavation study on this portion revealed that the latest faulting event occurred between 1,700 cal. B.P. to 1,310 cal. B.P. (255 A.D. -645 A.D.). The timing of the last faulting event at this study area coincides with the timing in the Gofukuji fault and Okaya fault. The active faults extending from the Matsumoto basin as far as the northwestern margin of the Suwa basin display the evidence for its recent reactivation at the same time.

著者

谷口 薫 渡辺 満久 鈴木 康弘 澤 祥

出版者

SEISMOLOGICAL SOCIETY OF JAPAN

雑誌

地震. 2輯 (ISSN:00371114)

巻号頁・発行日

vol.64, no.1, pp.11-21, 2011-08-25

被引用文献数

2

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The 150 km long Itoigawa-Shizuoka Tectonic Line Active Fault System (ISTL) in central Japan is one of the most active fault systems in Japan. Paleoseismologcal studies 1980s have revealed that the most recent event and the average recurence interval of the ISTL. The approximately 7 km long portion of the fault system between Matsumoto and Okaya has been regarded as a gap without any active fault trace. The gap namely the "Shiojiri Pass Gap" has long been taken as a segment boundary owing to the geometric discontinuity. Recent geomorphological analyses of the gap have demonstrated a through-going left-lateral slip assocaited with recent earthquakes in this area, based on aerial photograph interpretation and excavation studies. Excavation study on this portion revealed that the latest faulting event occurred between 1,700 cal. B.P. to 1,310 cal. B.P. (255 A.D. -645 A.D.). The timing of the last faulting event at this study area coincides with the timing in the Gofukuji fault and Okaya fault. The active faults extending from the Matsumoto basin as far as the northwestern margin of the Suwa basin display the evidence for its recent reactivation at the same time.