著者

野津 厚 山田 雅行 長尾 毅 入倉 孝次郎

出版者

公益社団法人 日本地震工学会

雑誌

日本地震工学会論文集 (ISSN:18846246)

巻号頁・発行日

vol.12, no.4, pp.4_209-4_228, 2012 (Released:2012-09-28)

参考文献数

40

被引用文献数

1

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2011年東北地方太平洋沖地震の際、震源断層に比較的近い宮城県から茨城県にかけての多くの地点で観測された0.2-1Hzの帯域の速度波形は明瞭なパルスによって特徴付けられている。これらの強震動パルスは、構造物に対して影響を及ぼしやすい周波数帯域に現れているという点で、内陸地殻内地震による強震動パルスと共通の特徴を有していると言える。海溝型巨大地震がもたらす強震動パルスも構造物に大きな影響を及ぼす可能性があり、今後、海溝型巨大地震に対する強震動予測、特に耐震設計を目的とする強震動予測を行う場合には、強震動パルスの生成を意識した震源のモデル化を行うことが重要と考えられる。本稿においては、まず、海溝型巨大地震による強震動パルスの生成事例を示す。次に、それらの再現を目的として構築された既往の震源モデルを整理し、強震動パルスを生じたと考えられる領域(強震動パルス生成域)の諸特性と地震規模との関係を調べる。

著者

鶴来 雅人 澤田 純男 入倉 孝次郎 土岐 憲三

出版者

Japan Society of Civil Engineers

雑誌

土木学会論文集 (ISSN:02897806)

巻号頁・発行日

vol.1999, no.612, pp.165-179, 1999-01-21 (Released:2010-08-24)

参考文献数

29

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本研究では, 大阪府全域を対象としてアンケート震度調査を実施し, 1995年兵庫県南部地震の詳細な震度分布を求めた. 得られた震度分布の信頼性を確認するため, 地震観測記録から算出される計測震度との比較および他機関が実施したアンケート震度調査結果との比較を行なった. その結果, 太田方式によるアンケート震度は計測震度で補正する必要があることが明らかとなった. そこで, 本調査結果に対しても補正を行い, 信頼性の高い震度分布を得た. さらに, 震度分布から見かけの震源, 伝播経路およびサイト特性を分離し, 断層破壊伝播による指向性の影響, 震度の距離減衰特性, サイト特性による高震度あるいは低震度域を明らかにした.

著者

入倉 孝次郎

出版者

自然災害科学会

雑誌

自然災害科学

巻号頁・発行日

vol.23, no.2, pp.153-154, 2004

著者

釜江 克宏 入倉 孝次郎

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.62, no.500, pp.29-36, 1997

参考文献数

30

被引用文献数

24 10

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The 1995 Hyogo-ken Nanbu earthquake struck Kobe and adjacent cities, one of the most densely populated area in western Japan, and killed more than 6,400 people and destroyed more than 150,000 buildings and houses and tens of highway and railroad bridges. It is very important to examine the ground motion characteristics in the severely damaged area during the mainshock for understanding how buildings and bridges performed and why they reached collapse. Unfortunately very few strong ground motions were recorded in the severely damaged areas during the mainshock. In this study, we attempt to estimate ground motion at severely damaged sites by using the empirical Green's function method (EGF method). We derive a best source model with three asperities after several try and error with forward modeling by the EGF method. We estimate strong ground motions at sites, where the mainshock was not recorded, using aftershock records. The synthesized motions in the near-fault region in Kobe were characterized by two large long-period (1 to 3 seconds) pulses due to the forward rupture directivity. Peak horizontal acceleration and velocity of the synthesized motions at the heavily damaged sites are about 1,000 cm/sec^2 and 130 cm/sec, respectively, while those at a rock site in near-fault region show about 300 cm/sec^2 and 60 cm/sec. The reason why so strong motions hit the heavily damaged sites is that the large long-period pulses which come from two asperities in the Kobe-side segment of the fault were further amplified by the basin edge effects.

著者

入倉 孝次郎 釜江 克宏

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.52, no.1, pp.129-150, 1999-06-30 (Released:2010-03-11)

参考文献数

33

被引用文献数

9

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We simulate strong ground motions during the 1948 Fukui earthquake with the JMA magnitude 7.1 based on a heterogeneous source model and the hybrid simulation technique. So far there are no existing source models available for simulating strong ground motions from the 1948 Fukui earthquake. Most of the source models have been assumed to have uniform slip distribution on rectangular fault plane. Such models could generate ground motions only available longer than several seconds, underestimating shorter period motions (<1sec) of engineering interest. The objective of this paper is to construct a heterogeneous source model for simulating strong ground motions in a broad period band during the 1948 Fukui earthquake. We assume two source models to examine: Model 1 is a reverse fault model determined from the analysis of geodetic data by YOSHIOKA (1974) and Model 2 is a normal fault model from strong motion displacement data by KIKUCHI et al. (1999). Heterogeneous slip distribution on fault plane is estimated based on the self-similar scaling relationships of seismic moment versus asperity areas and slips by Somerville et al. (1999). Then we obtained the standardized source model consisting of two asperities to have the average characteristics of asperities for the seismic moment of the Fukui earthquake. Relative locations and rupture times of the asperities on the fault plane are determined following the source model by KIKUCHI et al. (1999). The maximum asperity corresponding to the second event in their model has an area of 12×12km2 and slip of 1.7m and is located under the most heavily damaged area along the buried fault, known as the Fukui earthquake fault. The smaller asperity corresponding to the first event is located north of the maximum asperity. Rupture was initiated at the northern edge of the smaller asperity, propagated toward south, then broke to start the maximum asperity 7 seconds after the initial rupture. Large ground motions from both models, Model 1 and 2, are spread over the Fukui basin, although peak velocity distributions are rather different between the two models. Areas over 30% collapse ratio during the Fukui earthquake correspond to those with peak velocity over 60cm/s for Model 1 and over 80cm/s for Model 2. The level of the peak velocity in the areas with more than 30% collapse ratio are estimated to be over 80cm/s connected with both results by MOROI et al. (1998) and MIYAKOSHI and HAYASHI (1998). Pseudo velocity response spectra in the center of the Fukui basin for Model 2 have almost the same level of the observed ones at Takatori (TKT) and the simulated ones at Fukuike (FKI) within the damage belt during the 1995 Hyogo-ken Nanbu earthquake. We conclude that the damage distribution during the Fukui earthquake is well explained by strong ground motions simulated for Model 2 combined with the normal fault model by KIKUCHI et al.. (1999) and a standardized heterogeneous source model developed by SOMERVILLE et al. (1999).

著者

入倉 孝次郎 松田 時彦

出版者

ナショナルピーアール

雑誌

Energy for the future

巻号頁・発行日

vol.37, no.2, pp.4-12, 2013

著者

赤松 純平 古沢 保 入倉 孝次郎

出版者

京都大学防災研究所

雑誌

京都大学防災研究所年報. B = Disaster Prevention Research Institute Annuals. B (ISSN:0386412X)

巻号頁・発行日

vol.18, no.B, pp.11-21, 1975-04-01

著者

入倉 孝次郎 三宅 弘恵

出版者

学術雑誌目次速報データベース由来

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.110, no.6, pp.849-875, 2001

被引用文献数

25 94

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We propose a recipe to predict strong ground motions from scenario earthquakes which are caused by active faults. From recent developments in waveform inversion analysis for estimating rupture processes during large earthquakes, we have understood that strong ground motion is relevant to slip heterogeneity rather than total moment on the fault plane. The source model is characterized by three kinds of parameters, which we call : outer fault parameters, inner fault parameters, and extra parameters. The outer fault parameters are parameters characterizing the entire source area such as total fault length, fault width, and seismic moment. The total fault length (L) is related to the grouping of active faults, <I>i.e.</I> the sum of the fault segments. The fault width (W) is related to the thickness of the seismogenic zones. The total fault area S (=LW) follows the self-similar scaling relation with the seismic moment (M<SUB>0</SUB>) for moderate-size crustal earthquakes and departs from the self-similar model for very large crustal earthquakes. The locations of the fault segments are estimated from the geological and geomorphological surveys of the active faults and/or the monitoring of seismic activity. The inner fault parameters are parameters characterizing fault heterogeneity inside the fault area. Asperities are defined as regions that exhibit large slip relative to the average slip on the fault area. The relationship between combined area of asperities and seismic moment M<SUB>0</SUB> satisfies the self-similar scaling relation. The number of asperities is related to segmentation of active faults. The rake angles of slips on the asperities should be estimated from the geological survey and/or geodetic measurements. The extra fault parameters are related to the propagation pattern of rupture within the source area. Rupture nucleation and termination are related to the geometrical patterns of the active-fault segments. The recipe proposed here is to construct the procedure for characterizing those inner, outer, and extra parameters for scenario earthquakes. Then, we have confirmed that the scaling relations for the inner fault parameters as well as the outer fault parameters are valid for characterizing earthquake sources and calculating ground motions from recent large earthquakes, such as the 1995 Kobe (Japan) earthquake, the 1999 Kocaeli (Turkey) earthquake, and the 1999 Chi-Chi (Taiwan) earthquake. We have also examined the recipe for estimating strong ground motion during the 1948 Fukui (Japan) earthquake. The simulated ground motions clearly explain the damage distribution in the Fukui basin.

著者

堀内 茂木 入倉 孝次郎 中村 洋光 青井 真 山田 真澄 干場 充之 正木 和明 香川 敬生 正木 和明 倉橋 奨 香川 敬生 大堀 道広 福島 美光 山本 俊六 赤澤 隆士 松崎 伸一 呉 長江 ZHAO Jhon

出版者

独立行政法人防災科学技術研究所

雑誌

基盤研究(B)

巻号頁・発行日

2007

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東南海、南海、東海等の巨大地震発生時に、面的震源をリアルタイムで推定するための開発を行なった。P波部分の震度の距離減衰式を調べ、P波部分も震源域で飽和することが示された。震度の観測データやシミュレーションデータを使い、震源域の広がりをリアルタイムで推定する手法を開発した。また、速度や加速度の最大値から、断層近傍であるかを判定し、震源域を推定する方法も開発し、リアルタイムでの巨大地震情報配信の目処がたった。

著者

松島 信一 川瀬 博 佐藤 智美 入倉 孝次郎 岩田 知孝

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.1995, pp.191-192, 1995-07-20