Chuetsu-oki Earthquake Research Articles

Array Back-Projection Imaging of the 2007 Niigataken Chuetsu-oki Earthquake Striking the World's Largest Nuclear Power Plant

The 2007 Niigataken Chuetsu-oki earthquake occurred near the Kashiwazaki–Kariwa nuclear power plant in Japan, the largest in the world. The strong motions were recorded by seven seismometers installed at the foundation slab (base-mat) of the plant and exceeded the design level of the ground motion for the plant. The strong motion observed by the seismographs in and around the plant show high coherency with three significant pulses. In order to understand the cause of these pulses, the rupture process of the earthquake was estimated using these seismograms. The seismograph network was taken into account as a dense array and semblance-enhanced waveform stacking was performed. By projecting the power of the stacked waveforms onto the fault plane, the asperities that generated significant pulses were successfully separated. The first and third pulses were generated at the hypocenter and the southwest edge of the rupture zone, respectively. The rupture propagated toward the southwest and terminated offshore from the power plant. The overall pattern of the imaged asperities coincides well with the slip distribution determined by conventional waveform inversions.

Source process for complex fault system of the 2007 Chuetsu-oki, Niigata, Japan, earthquake

AbstractThe 2007 Chuetsu-oki earthquake occurred in the offshore area of Niigata Prefecture, central Japan, on 16 July 2007. The aftershock distribution shows two fault planes, dipping to the northwest and southeast, respectively, which form a cross-sectional “V” pattern. We analyze the kinematic source process for the two fault planes consistent with the aftershock distribution using teleseismic body waveform data. Our results indicate that the mainshock initiated rupture on both faults northeast of their intersection and that the rupture propagated unilaterally southwestward along the southeast-dipping fault. The maximum slip is 1.6 m on the southeastdipping fault, and the seismic moments of northwest- and southeast-dipping faults are 8.0 × 1017N m (Mw5.9) and 7.5 × 1018N m (Mw6.5), respectively. The forward modeling of geodetic displacement from the obtained fault model is consistent with the GPS and InSAR measurements. Successive conjugate reverse faults around the source region are identified from the reflection seismic sections. We presume that stress changes and complicated structures in property and geometry around the source region are the dominant causal factors for generating the complexity of coseismic fault system.

In situ Measurements of Tide Gauge Response and Corrections of Tsunami Waveforms from the Niigataken Chuetsu-oki Earthquake in 2007

Linear and nonlinear responses of ten well-type tide gauge stations on the Japan Sea coast of central Japan were estimated by in situ measurements. We poured water into the well or drained water from the well by using a pump to make an artificial water level difference between the outer sea and the well, then measured the recovery of water level in the well. At three tide gauge stations, Awashima, Iwafune, and Himekawa, the sea-level change of the outer sea is transmitted to the tide well instantaneously. However, at seven tide gauge stations, Nezugaseki, Ryotsu, Ogi, Teradomari, Banjin, Kujiranami, and Naoetsu, the sea-level change of the outer sea is not always transmitted to the tide well instantaneously. At these stations, the recorded tsunami waveforms are not assured to follow the actual tsunami waveforms. Tsunami waveforms from the Niigataken Chuetsu-oki Earthquake in 2007 recorded at these stations were corrected by using the measured tide gauge responses. The corrected amplitudes of the first and second waves were larger than the uncorrected ones, and the corrected peaks are a few minutes earlier than the uncorrected ones at Banjin, Kujiranami, and Ogi. At Banjin, the correction was significant; the corrected amplitudes of the first and second upward motion are +103 cm and +114 cm, respectively, while the uncorrected amplitudes were +96 cm and +88 cm. At other tide gauge stations, the differences between the uncorrected and corrected tsunami waveforms were insignificant.

シンポジウム６‐３ 神経難病および医療ネットワーク 災害に備えた難病医療ネットワークと災害時の対応‐２回の地震を経験して

Anti-disaster measures along with disaster medicine aims at reducing loss of property and life and facilitating grief work of the suffered people. In contrast the care system for patients with intractable disease has the same aim. According to the experiences of two large earthquakes including Chuetsu (2004) and Chuetsu-oki earthquake (2007), earthquake-resistant buildings are necessary for maintaining hospital function as well as reviving community after occurrence of large earthquake. A list of patients living with ventilator and their individual care plan designed for disaster need to be prepared to transport each patient to the hospital at appropriate timing, when electricity and visiting nurse care system are damaged. Satellite telephone is very useful for communicating with such patients and medical teams because telephone connection is limited to only the specific calling number just after occurrence of earthquake.

Medical Students Provide Volunteer Services Following the Chuetsu-Oki Earthquake

Medical Students Provide Volunteer Services Following the Chuetsu-Oki Earthquake

Deformation analyses of river dike on liquefiable ground affected by different earthquake motions

Severe damages of river dikes caused by liquefaction have been often observed. In previous earthquakes, it has been reported that many river dikes were deformed by the liquefaction during earthquake. The river dike in the middle region of Shinano River is built on the loosely deposited sandy layers. Therefore, a large deformation of the river dike by the liquefaction is expected. It is very important to understand the deformation mechanism of the river dike by liquefaction in order to prevent a future damage of river dike along Shinano River. In this study, effective stress based finite element analyses were carried out by the program code LIQCA to reproduce the past damage and to compare the damage of the river dike by different earthquake motions. Three earthquake motions by the 1964 Niigata earthquake, the 2004 Niigataken Chuetsu earthquake and the 2007 Niigataken Chuetsu-Oki earthquake had different duration time and acceleration amplitude. The comparisons among damages by three earthquakes were carried out. As the results, it was confirmed that the duration time and the acceleration amplitude of earthquake motion were key factors which affect the damage of the river dike.

ユニバーサルジョイントの破損実験と強度解析(機械力学,計測,自動制御)

This paper discusses research on the strength analysis and damage experiments of a universal joint. The Kashiwazaki Kariwa nuclear power plant suffered damage under the Niigata Chuetsu-oki earthquake, which occurred on July 16, 2007. The earthquake motion damaged a driving shaft coupling of an overhead traveling crane of unit 6 nuclear reactor building. The damaged portion consisted of a universal joint. In this research, the cause of damage of the universal joint is studied, and damage experiment and stress analysis of the miniature model of a universal joint are conducted. As a cause of the damage, it is thought that the universal joint was loaded with torque under the earthquake motion. In the experiment, a miniature model of the universal joint is loaded with the torque to be damaged. The torque of damage is measured. The failure modes are observed. Similarly, in the analysis by 3DCAD (Three Dimensional Computer Aided Design) and CAE (Computer Aided Engineering), the miniature model is loaded with the torque to be damaged. The analytical result is compared with the experimental result. The analytical result agrees with the experimental result.

EFFECT OF DAMPING OF PORE WATER ON THREE DIMENSIONAL NONLINEAR SEISMIC RESPONSE ANALYSIS OF GROUND

Three-dimensional nonlinear seismic response analysis of ground was presented in which any special engineering judgment to determine analytical parameters of the ground was not required. To examine the effectiveness of the method, the vertical array strong motions recorded in Kashiwazaki Kariwa Nuclear Power Station during the 2007 Niigata-ken Chuetsuoki earthquake was simulated. When using only hysteresis damping due to shearing deformation in the analysis, the vertical motion showed an excessive response due probably to the resonance of the pore water. When a damping of about 10% was given to the pore water, in contrast, the analysis was able to reproduce the observed three-dimensional ground motion with a reasonable degree of accuracy.

Source Modeling of the 2007 Niigataken Chuetsu-oki Earthquake Using the Empirical Green's Function Method

The 2007 Niigataken Chuetsu-oki earthquake (MJMA6.8) occurred on July 16th, 2007. In this study, we estimate a source model of this earthquake through forward modeling of local strong motion records using the empirical Green's function method. The target frequency range of this modeling is broadband (0.3 Hz to 10 Hz). As the result, the first asperity was estimated that it was located on the NW-dipping fault plane including the hypocenter, and the rupture then transferred to the conjugated fault plane (SE-dipping plane). On the SE-dipping plane, two asperities are identified: one is located just near the first asperity (the second asperity); the other is off the coast of Kashiwazaki city (the third asperity). The estimated three asperities are located in the gaps of the aftershock distribution. Our source model can successfully reproduce strong motion in a wider area than the modeling area selected for source estimation. The estimated stress drop from our source model is almost 15 to 20 MPa, and it is similar to the stress drop empirically expected from the seismic moment and area of asperities.

Mechanism of Fracture of Concrete Canal Joints during the Niigataken Chuetsu-oki Earthquake

Mechanism of Fracture of Concrete Canal Joints during the Niigataken Chuetsu-oki Earthquake

Investigation and Repair Works of Kouchi-Dam caused by The Niigataken Chuetsu-oki Earthquake(2007) in Kashiwazaki-City Centoral Japan

Investigation and Repair Works of Kouchi-Dam caused by The Niigataken Chuetsu-oki Earthquake(2007) in Kashiwazaki-City Centoral Japan

中越沖地震の柏崎刈羽原子力発電所影響評価研究分科会の活動 : 原子力発電所の機器等の地震安全に関する技術課題と研究・開発ロードマップの検討(中越沖地震の柏崎刈羽原子力発電所影響評価研究分科会,<特集>第13回動力・エネルギー技術シンポジウム)

This paper describes technical issues for the seismic safety of nuclear power plant components and also shows preliminary roadmaps for the solution of the issues. After the Chuetsu-oki earthquake of July 2007, research committees were established in JSME and AESJ for the discussion of the effect of the earthquake on NPP components. Ten technical issues due to the earthquake are pointed out and the discussion concerning the roadmaps has started to solve each issue. The goal of the activity is for the advanced design methodology with seismic safety.

Temporal Change of S-wave Velocity Observed at Vertical Array in the Kashiwazaki-Kariwa Nuclear Power Plant during, before and after the 2007 Niigataken Chuetsu-oki Earthquake

東京電力株式会社柏崎刈羽原子力発電所において観測された2007 年新潟県中越沖地震とその前後の地震記録が公開された．これらの記録は，震源近傍の非常に高密度の地震記録として極めて貴重なものである．本研究では，NIOM 法を東京電力株式会社柏崎刈羽原子力発電所のサービスホール（KSH）の鉛直アレーにおける観測記録に適用して，2007 年新潟県中越沖地震とその前後のS 波速度の経時変化を検討した．その結果，表層（地表～地下50m）と中間層（地下50m～100m）では本震主要動時に顕著なS 波速度の低下が見られること，その一方で，主要動直後からS 波速度が増加し始めていることなどから，これらの層においても大規模な液状化は生じなかったものと考えられること，基盤層では主要動時においてもS 波速度の低下はごくわずかであり，強震動による非線形化の影響は殆ど生じていないと考えられることなどを指摘した．

中越沖地震の柏崎刈羽原子力発電所影響評価研究分科会の活動 : 重要度分類について(中越沖地震の柏崎刈羽原子力発電所影響評価研究分科会,<特集>第13回動力・エネルギー技術シンポジウム)

中越沖地震の柏崎刈羽原子力発電所影響評価研究分科会の活動 : 重要度分類について(中越沖地震の柏崎刈羽原子力発電所影響評価研究分科会,<特集>第13回動力・エネルギー技術シンポジウム)

中越沖地震の柏崎刈羽原子力発電所影響評価研究分科会の活動 : 原子力発電所の機器等の地震安全に関する建屋・機器設計の余裕の考え方(中越沖地震の柏崎刈羽原子力発電所影響評価研究分科会,<特集>第13回動力・エネルギー技術シンポジウム)

中越沖地震の柏崎刈羽原子力発電所影響評価研究分科会の活動 : 原子力発電所の機器等の地震安全に関する建屋・機器設計の余裕の考え方(中越沖地震の柏崎刈羽原子力発電所影響評価研究分科会,<特集>第13回動力・エネルギー技術シンポジウム)

中越沖地震の柏崎刈羽原子力発電所影響評価研究分科会の活動(概要)(中越沖地震の柏崎刈羽原子力発電所影響評価研究分科会,第13回動力・エネルギー技術シンポジウム)

The Niigataken Chuetsu-oki earthquake attacked the Kashiwazaki-Kariwa Nuclear Power Plant (NPP) of Tokyo Electric Power Company on July 16th in 2007. The three units under normal operation and one unit under startup stage were safely shut down. The other three units are in refueling and maintenance outage. Althogh the NPP were safely controlled, even in the very strong earthquake, there were several unexpected events and many troubles. In order to investigate the influence of the earthquake on the NPP, the Research Committee had been started in the Division of Power and Energy System in JSME. This note summarizes the activities of the Research group.

中越沖地震の柏崎刈羽原子力発電所影響評価研究分科会の活動 : 広報と報道のあり方(中越沖地震の柏崎刈羽原子力発電所影響評価研究分科会,<特集>第13回動力・エネルギー技術シンポジウム)

中越沖地震の柏崎刈羽原子力発電所影響評価研究分科会の活動 : 広報と報道のあり方(中越沖地震の柏崎刈羽原子力発電所影響評価研究分科会,<特集>第13回動力・エネルギー技術シンポジウム)

経験的グリーン関数法を用いた２００７年新潟県中越沖地震の震源のモデル化

The 2007 Niigataken Chuetsu-oki earthquake (MJMA6.8) occurred on July 16th, 2007. In this study, we estimate a source model of this earthquake through forward modeling of local strong motion records using the empirical Green's function method. The target frequency range of this modeling is broadband (0.3 Hz to 10 Hz). As the result, the first asperity was estimated that it was located on the NW-dipping fault plane including the hypocenter, and the rupture then transferred to the conjugated fault plane (SE-dipping plane). On the SE-dipping plane, two asperities are identified: one is located just near the first asperity (the second asperity); the other is off the coast of Kashiwazaki city (the third asperity). The estimated three asperities are located in the gaps of the aftershock distribution. Our source model can successfully reproduce strong motion in a wider area than the modeling area selected for source estimation. The estimated stress drop from our source model is almost 15 to 20 MPa, and it is similar to the stress drop empirically expected from the seismic moment and area of asperities.

中越沖地震の柏崎刈羽原子力発電所影響評価研究分科会の活動 : 柏崎刈羽原子力発電所現地調査結果(中越沖地震の柏崎刈羽原子力発電所影響評価研究分科会,<特集>第13回動力・エネルギー技術シンポジウム)

Due to the Niigataken Chuetsu-oki earthquake on 16 July 2007, Tokyo Electric Power Company's Kashiwazaki-Kariwa Nuclear Power Plant (NPP) suffered from quakes exceeding design basis. The plants consisting of seven reactors and related facilities performed its essential functions required in the nuclear safety design such as "stop", "cool", and "confine" as designed, no matter whether in operation or in outage. The fact our group found through surveys in the site tells us that the experience of the Kashiwazaki-Kariwa NPP provides all NPPs with very important scientific findings.

災害弱者の生活と食事―現状と課題―

Dead′occurring earthquakes occurred 8 times every 14 years from Hanshin-Awaji (Kobe) Earthquake (January 17, 1995) to Iwate and Miyagi inland type earthquake (June 14, 2008) in Japan. The personal suffering due to the earthquake reached not only casualties but also lives in the refuge. 317,000 people did inconvenient life by in the refuge in Hanshin-Awaji (Kobe) Earthquake, 100,000 people in the Mid Niigata Earthquake, and 12,000 people in Niigata Chuetsu-oki Earthquake. As for the meal offer in the refuge, it was suggested that the meal considered to vulnerable people such as the aging people, the baby and people having the swallowing function trouble or and dietetic treatment of the struck weak, and foreigners who had the food taboo in the reason of the religion etc. Qualitative correspondence in the meal offer when struck seemed in the future. I think that it is important examine three aspects of “Object person”, “Food”, “ Substitution of the lifeline”, and two systems “Self-help, mutual assistance, and public assistance”, and “Savings and rescue”.