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.51, no.2, pp.211-228, 1998-10-15 (Released:2010-03-11)

参考文献数

31

被引用文献数

3 22

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According to SHIMAZAKI (1986), the large and small Japanese intraplate earthquakes obey the different scaling laws: M0∝L3 for small events but M0∝L2 for large events, where L and M0 are fault length and seismic moment, respectively. This is caused by the fact that the fault widths W for the large events are bounded by the thickness of the seismogenic layer in the crust. We examined the relations among source parameters for 33 Japanese intraplate earthquakes from 1885 to 1995 and confirmed the validity of the results obtained by SHIMAZAKI (1986) for the events of M=5 to 8, where M is the magnitude in the scale of the Japan Meteorological Agency (JMA). Relations between source parameters and JMA magnitude M were also derived from the relations among source parameters, using the M0-M relation by TAKEMURA (1990).SHIMAZAKI (1986) also indicated the offset of the L-M0 relation at the transition between small and large earthquakes, and suggested that the offset appeared to be due to the difference in boundary conditions between buried and surface faults. We found an offset from 6.5 to 6.8 in the JMA magnitude M, as well as the offsets of a factor of about 2 in D and M0, but no offset in L and W, where D is the average slip of the fault. Also we found that almost all events with M≥6.8 accompanied the surface faults, while most of the events with M≤6.5 did not accompany any surface fault. These results strongly supported that the offsets in D, M0, and M were caused by the surface fault breaks for the large earthquakes. Furthermore, we examined the relation between the damages from the Japanese intraplate earthquake and its JMA magnitude M. The damages suddenly increased from M=6.5 to M=6.8. The scaling law obtained above gave the large earthquake a strip fault whose location was very shallow. Because of these conditions, the intraplate earthquakes with M≥6.8 bring about strong ground motions in the wide area.

著者

神田 克久 武村 雅之 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.56, no.1, pp.39-57, 2003-06-02 (Released:2010-03-11)

参考文献数

30

被引用文献数

6

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The method of the inversion analysis to evaluate the distribution of seismic energy radiated from an earthquake fault plane based on seismic intensity distribution data has been developed. The fault plane is divided into small sub-faults. The optimized seismic energy distribution of each sub-fault is calculated using the least square method to minimize the error between evaluated and observed seismic intensities.The energy distribution of a seismic fault is related to seismic intensity using the attenuation formula with equivalent hypocentral distance. The parameters of the attenuation formula are obtained from a regression analysis with measured seismic intensity data of recent moderate earthquakes.The forward analyses using an assumed model are performed to verify the accuracy of the inversion analysis and to evaluate the effect of factors such as the standard deviation of seismic intensity, constraint condition of inversion analysis and configuration of observation stations.Finally, the method is applied to the Showa Tonankai earthquake in 1944 and the Showa Nankai earthquake in 1946 and the result is compared with the tsunami and strong motion waveform inversion results to confirm the efficiency and applicability of the method.

著者

武村 雅之

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.108, no.4, pp.440-457, 1999-08-25 (Released:2009-11-12)

参考文献数

47

被引用文献数

2

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Immediately after the 1923 Kanto Earthquake (M=7.9), two large aftershocks of M=7.2 and 7.3 occurred in succession somewhere in the southern Kanto district. The first aftershock occurred about 3 minutes after the main shock and the second about 4.5 minutes after the main shock. Strong ground motions from these events and locations of their epicenters were examined mainly from data of 548 descriptions of personal experiences. It was deduced from them that shaking due to the first aftershock was severe in the Tokyo Metropolis and eastern Kanagawa prefecture. In consequence, there were many descriptions in the Tokyo Metropolis that the shaking was as strong as that due to the main shock and caused extensive damage.On the other hand, there were few descriptions for the first aftershock in the western area of the southern Kanto district, which is western Kanagawa prefecture, Yamanashi prefecture, and eastern Shizuoka prefecture. However, shaking due to the second aftershock was strong in this area. Some people living near the boundary of the three prefectures described that its shaking was as strong as that due to the main shock. Comparing the facts described in these personal experiences with the distributions of seismic intensities from other M=7 class earthquakes occurring in the southern Kanto district after the 1855 Ansei Edo Earthquake, it was concluded that the epicenter of the first aftershock was located in and around northern Tokyo Bay and that the epicenter of the second aftershock was in eastern Yamanashi prefecture. The result for the second aftershock was consistent with the epicenter determined from the seismic records by the Kumagaya Meteorological Observatory and with the epicentral distance estimated from data of S-P time at the Gifu Meteorological Observatory. The characteristics of the sequence of strong shakings within 5 minutes after the 1923 Kanto Earthquake could be elucidated in the southern Kanto district from the results of the present study.

著者

諸井 孝文 武村 雅之

出版者

北海道大学大学院理学研究院自然史科学部門(地球物理学)

雑誌

北海道大学地球物理学研究報告 (ISSN:04393503)

巻号頁・発行日

vol.73, pp.101-116, 2010-03-19

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Datasets of structural damage and regional damage due to past earthquakes are not only useful to know the actual state of each event but also effective for strong ground motion predictions and damage mitigations of future earthquakes. In this paper, several considerations are illustrated concerning strong ground motion research and data processing analysis. Especially, the activity to make research results contribute to society is discussed based on three examples of earthquake damage data analysis. The examples shown here describe that the well known notion in general, what is called common knowledge, does not necessarily have high reliability, and that the lack of confirmation of the data accuracy misleads the conclusion of research results beyond common sense. From these examples, the importance of an empirical research policy as well as a reasonable research policy is discussed. And it is pointed out that the information exchange among the researchers in various fields will be very effective for the development of the strong ground motion research.

著者

中西 龍二 山崎 敏彦 瓜生 満 永野 正行 武村 雅之

出版者

一般社団法人日本建築学会

雑誌

学術講演梗概集. B-2, 構造II, 振動, 原子力プラント (ISSN:13414461)

巻号頁・発行日

vol.2006, pp.57-58, 2006-07-31

著者

加藤 研一 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.49, no.1, pp.75-83, 1996-05-24 (Released:2010-03-11)

参考文献数

27

被引用文献数

1

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Direction of rupture propagation φ and fault length L for the 1994 Sanriku-Haruka-Oki earthquake are evaluated from the azimuthal dependence in duration of strong ground motion observed at eleven stations along the Pacific coast of Tohoku and Hokkaido region. After defining the strong motion duration D as the time interval between onset of S wave and 85% of cumulative power curve derived from 5 to 10Hz band-pass filtered accelerogram, the azimuthal dependence of D is examined. We find that D systematically shows directivity: D is the shortest at northern part of Tohoku and the longest at southern part of Tohoku and eastern edge of Hokkaido. By making use of the directivity on observed strong motion durations, we apply the method by IZUTANI and HIRASAWA (1987) to deducing φ and L together with VR/β, where VR and β are rupture velocity and S wave velocity. Assuming that rupture initiated from the epicenter determined by the Japan Meteorological Agency (JMA), we obtain L/VR=53, VR/β=0.62, and φ=W9°N (case 1). This result indicates that the rupture was headed toward northern part of Tohoku, and terminated near the western end of aftershock area. Detailed source-process inversion [for example, SATO et al. (1996)] suggests that main rupture nucleated near the center of aftershock area, corresponding to the epicenter determined by Harvard University. We redo the calculation assuming that the rupture initiated from the Harvard epicenter, then resulting in L/VR=28, VR/β=0.71, and φ=W18°N (case 2). This result also indicates that the rupture propagated toward northern part of Tohoku, and terminated at the western end of aftershock area. SATO et al. (1996) suggest that this earthquake consists of threestage rupture process: the first and the second sub-events corresponding to JMA and Harvard epicenter, respectively, and the third sub-event located near the western end of aftershock area at the distance of about 50km from Hachinohe city. The location where rupture terminated in both cases of this study is consistent with the location of the third sub-event, confirming that the rupture extended to the western end of aftershock area.

著者

加藤 研一 武村 雅之 八代 和彦

出版者

日本建築学会

雑誌

日本建築学会構造系論文集 (ISSN:13404202)

巻号頁・発行日

vol.64, no.521, pp.33-40, 1999

被引用文献数

5 4

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The excitation strengths of high-frequency strong motions from intermediate depth earthquakes (IDE) are investigated from the peak ground accelerations (PGA) of 13 events occurring at Eastern Japan. 13 shallow earthquakes at the same region are also analyzed for comparison. The observed PGA's from IDE's show systematically larger amplitude than the empirical average obtained from shallow events by a factor of 1.6. These deviations show regional variation: the IDE's at the Hokkaido and the Kanto regions excite larger PGA than those at the Tohoku region. It is concluded that the focal depth is a key parameter to control the amplitude of PGA rather than focal mechanism and/or fault type.

著者

藤堂 正喜 羽鳥 敏明 千葉 脩 高橋 克也 武村 雅之 田中 英朗

出版者

日本建築学会

雑誌

日本建築学会構造系論文集 (ISSN:13404202)

巻号頁・発行日

vol.60, no.475, pp.45-54, 1995

被引用文献数

6 4

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Using seismic records observed in 4 borehole arrays, characteristics of vertical seismic motions in sedimentary layers are investigated. The results are as follows. 1) P-waves having intensive effect to vertical component are propagating within sedimentary layers even after the S-wave onset time (S-wave part). 2) Frequency dependent Q-values for P-waves (Qp) in Tertiary sediment layers obtained from the optimal analyses to spectral ratios have the tendency to be identical with Q-values for S-waves (Qs) with the same wavelength. 3) Observed vertical motions in upper ground can be simulated by the multiple reflection theory of P-waves based on the optimized velocities and Q-values.

著者

丹羽 正徳 山中 浩明 武村 雅之 池浦 友則

出版者

一般社団法人日本建築学会

雑誌

学術講演梗概集. B, 構造I (ISSN:09150129)

巻号頁・発行日

vol.1993, pp.175-176, 1993-07-25