著者

林 豊 前田 憲二

出版者

Japanese Society for Active Fault Studies

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.2009, no.30, pp.27-36, 2009

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Six active fault zones have been selected on the basis of the reports on the long-term evaluation of active faults published until 2008 by the Earthquake Research Committee, Headquarters of Earthquake Research Promotion (ERC/HERP); the paleoseismic activity data of these zones reveal three or more earthquake recurrence intervals. Using the maximum likelihood method, seven probability density functions of a renewal process model are compared in order to determine the function that best fit the paleoseismic activity data of these active fault zones.<br>The exponential distribution model obtained by using the maximum likelihood method does not clearly reveal the earthquakes recurrence intervals. In contrast, the results obtained by using six other statistical models, i.e., Brownian passage time (BPT) distribution, lognormal distribution, gamma distribution, Weibull distribution, double-exponential distribution, and normal distribution, reveal the earthquake recurrence intervals. Thus, the new paleoseismic activity data of major active zones in Japan confirm the provisional conclusion of ERC/HERP, i.e., the exponential distribution does not clearly show the earthquake recurrence intervals. On the other hand, differences among the goodness of fit of the six models excluding the exponential distribution are small.<br>In 2001, ERC/HERP stated that when renewal process model with the BPT distribution is applied to the data of the occurrence intervals of earthquakes in the inland active fault zones in Japan, the aperiodicity parameter of the distribution should be set to 0.24 as a value common to all active faults. The aperiodicity parameter obtained by applying the same method to the data of the six active fault zones is equal to 0.44. Although the aperiodicity parameters, obtained by using the maximum likelihood method, reported in the ERC/HERP's report range between 0.17 and 0.29, those obtained in this study range between 0.09 and 0.66. Thus it is inappropriate to assume the same aperiodicity parameter for all the inland active fault zones in Japan.

著者

杉山 英男 寺田 宙 出雲 義朗 宮田 昌弘 渡辺 芳則 土屋 鍛 遠藤 泰吾 吉田 昭夫 前田 憲二

出版者

公益社団法人 日本アイソトープ協会

雑誌

RADIOISOTOPES (ISSN:00338303)

巻号頁・発行日

vol.49, no.12, pp.617-622, 2000-12-15 (Released:2011-03-10)

参考文献数

10

著者

高山 博之 黒木 英州 前田 憲二

出版者

気象庁気象研究所

雑誌

Papers in Meteorology and Geophysics (ISSN:0031126X)

巻号頁・発行日

vol.58, pp.127-134, 2007 (Released:2007-11-01)

参考文献数

15

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すべり速度・状態依存摩擦構成則を平面および3次元の形状をしたプレート境界面に適用し,東南海および南海地震の発生順序に関するシミュレーションを行った。平面のプレート境界では,プレートの形状の影響がないので,東南海・南海地震のそれぞれのアスペリティの大きさおよび摩擦係数(a-b)の大きさの影響を調べた。アスペリティの大きさおよびa-bの絶対値が同じ場合(基本モデル)は,どちらかが先に起こる傾向は見られないことがわかった。アスペリティの大きさまたはa-bの絶対値が異なる場合は,いずれも小さい方が先に起きた。前者は応力の集中の早さの違いに起因し,後者は応力降下量の大きさの違いに起因する。プレート境界を3次元の形状にした場合についてもシミュレーションを行った。東南海と南海のアスペリティの大きさとa-bの大きさを同じにし,両アスペリティのa-bの絶対値を基本モデルと同じにした場合は東南海から先に起き,10%小さくすると南海から先に起こるようになった。これは東南海の東端からの応力の集中の早さと紀伊半島沖の安定すべりによる南海側での応力集中の早さの関係がa-bの値の大小で入れ替わるためと考えられる。

著者

弘瀬 冬樹 前田 憲二

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.70, pp.21-40, 2017-05-10 (Released:2017-09-07)

参考文献数

32

被引用文献数

1 1

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Frequency-magnitude distributions are generally expressed by the Gutenberg-Richter (G-R) law. However, frequency-magnitude distributions are sometimes a convex-upward curve rather than a straight line, departing from the G-R law. An η value originally introduced by Utsu (1978) is an indicator that represents the degree of deviation from the G-R law. We investigate η values before and after six M7-9 class mainshocks off the Pacific coast of eastern Japan. The η values tend to become small (i.e., the distribution deviates from the G-R law) before the mainshocks, and then increase (i.e., recovering to the G-R law). Taking this characteristic into account, we suggest a simple and challenging earthquake forecast model based on η values. Probability gain of the optimized forecast model by a retrospective test becomes 2.24-3.03, and the alarm rate and the truth rate become 100% and 0.14-0.47%, respectively. According to the result of the forecast model applied to the latest seismicity, we should pay attention to seismicity off the coast southeast of Kanto district.

著者

高木 朗充 高山 博之 前田 憲二 中村 雅基 黒木 英州 ト部 卓

出版者

特定非営利活動法人 日本火山学会

雑誌

日本火山学会講演予稿集 2004 (ISSN:24335320)

巻号頁・発行日

pp.76, 2004-10-19 (Released:2017-02-10)

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

伊藤 喜宏 岡田 知己 松澤 暢 海野 徳仁 長谷川 昭 前田 憲二

雑誌

日本地震学会講演予稿集 = Programme and abstracts, the Seismological Society of Japan

巻号頁・発行日

vol.1999, no.2, 1999-11-09

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

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.62, no.4, pp.193-207, 2010-03-15 (Released:2012-03-26)

参考文献数

26

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We found eight M 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 M 4, which occurred close to the hypocenters of the M 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 M 5 quakes, indicating that the M 5 events triggered the group C events whose asperity had suffcient strain energy. No earthquake exceeding M 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 M 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 M 5 event may be accompanied by an M 4 quake that could rupture the asperity of group C within one week.