1995年1月17日日本兵库县南部7.2级地震的特征

叙述了１９９５年１月１７日发生在日本兵库县南部７．２级地震的主震和余震分布、发震断层、震前的空区现象、震源机制解及区域应力场等特征，并对该次地震的发生与周围地体应力环境的关系等问题进行了探讨。     

1995年1月17日兵库县南部地震的震源机制

兵库县南部地震于１９９５年１月１７日５时４６分（ＪＳＴ;ＪＳＴ＝ＧＭＴ＋９ｈ）发生在兵库县南部的活动断层上,对几个城市尤其是神户造成了严重的破坏。我们通过对宽频带及强地面运动地震图的分析确定了本次地震的震源机制及大小（地震矩和震级）。由长周期矩心矩和量反演的震源机制是,走向、倾角、滑动角分别为２３３°,８３°,１６９°,补偿线性偶极向量分量小（１．５％）,Ｍ０＝３．０×１０＾１９Ｎｍ,Ｍｗ＝６．９     

1995年1月17日日本兵库县南部地震概况综述

１９９５年１月１７日,强烈的日本兵库县南部地震袭击了日本近畿地方的广大地区,这次灾难性的地震是半个世纪以来在日本发生的规模最大的一次内陆地震,它使日本遭受了一次出乎意料的严重破坏,打破了“日本安全”的神话,将对今后的地震预报和防灾对策研究产生重大的影响,因此,这次地震引起了日本和世界各国的极大关注。本文将对这次地震作一综合介绍。     

1995年1月17日日本兵库县南部地震现场调查概况

１９９５年１月１７日日本兵库县南部淡路岛发生７．２级地震后，正在工作的本文作者亲临地震灾区，进行了现场调查，作者以日记的形式叙述了现场调查情况，此外，他还给出了自己对灾害的分析。     

1995年1月17日日本阪神7.2级地震的构造条件研究

从地质构造背景、余震活动 、地震地表破裂及其位移分布特征和强地面运动等方面，分析了1995年1月17日日本阪神7.2级地震发震构造的几何学和动力学特点，认为野岛断裂和六甲山断裂走向相同，但倾向相反，上升盘与下降盘呈对角对称分布，属于逆走滑断裂．它们构成一条枢纽性走滑断裂，阪神地震就发生在该断裂的枢纽轴部，走滑断裂的枢纽运动导致了此次强震的孕育和发生．走滑断裂的枢纽运动常常伴随着大地震的发生，其动力学原因可以通过矩形截面梁扭转的应力分析来模拟．在一定的震中距范围内，地震地表破裂的位错量、余震密集程度以及峰值加速度随震中距的变化规律，有如在扭转的矩形截面梁内部从中心向周围的剪切应力大小的改变． 最后，从特定的地质构造环境和构造力学条件，分析了神户市地震破坏最严重地区的分布特点．本文的研究结果不仅在识别中长期地震危险区，而且在合理地建立地震灾害预测模型等方面都有一定的应用价值.      

日本兵库县南部地震强地震动的传播特性

依据神户海洋气象台、大阪气象台、神户港岛、神户大学、神户本山小学、尼崎及大阪福岛的强震记录，分析了强地震的走时和传播特性，指出大阪盆地的厚沉积层是造成Ｓｔ波在神户和大阪到时发生延迟的原因，由于断层在空间上的分布造成一些强震记录的波形差异。     

日本兵库县南部地震调查与中国唐山大地震的比较

叙述了１９９５年１月日本兵库县南部地震的强地面运动特征，并与１９７６年中国唐山地震的地面运动特征进行了对比，讨论了日本地震后次生灾害——火灾的残酷性，并分析了该次地震的前兆现象     

1995年兵库县南部地震主震震源的再确定

前言１９９５年１月１７日发生了兵库县南部地震。在气象厅（１９９５）公布震源以后,气象厅（１９９５）和京都大学防灾研究所（１９９６）又分别公布了各自修定的震源结果。但仍存在两个单位在震源附近没有或很少有观测点,而且观测点的方位偏向一边,不均匀,同时由于...     

Regional seismicity triggered by the Hyogo-Ken Nanbu, Japan, M =7.2 earthquake on January 17, 1995

The time and spatial feature of the regional seismicity triggered by the Hyogo-Ken Nanbu, Japan, M=7.2 earthquake on January 17,1995, was studied. The concerned region is about several hundred kilometers in length and breadth surrounding the epicenter (33°～37°N, 133°～138°E). It is divided into 16 subregions. The seismicity of these subregions from January of 1976 to June of 1996 has been analyzed. It is showed that,① there were significant seismicity changes in 10 subregions triggered by the Hyogo-Ken Nanbu, Japan, M=7.2 earthquake on January 17, 1995. These changes passed a Z statistic test exceeding 0.95 confidence level and the greatest epicenter distance of these subregions was 280 km;②seismicity changes were triggered within 1～5 days in three subregions near the main shock while in other subregions the seismicity changes were triggered within several ten days after the main shock;③ the greatest triggered event is 5.4, which is about the same size as the greatest aftershock;④the regional stress change resulted from the main shock may be the triggered mechanism of the regional seismicity.     

Precursory Activation of Seismicity in Advance of the Kobe, 1995, M = 7.2 Earthquake

—A succession of precursory changes of seismicity characteristic to earthquakes of magnitude 7.0–7.5 occurred in advance of the Kobe 1995, M = 7.2, earthquake. Using the Japan Meteorological Agency (JMA) regional catalog of earthquakes, the M8 prediction algorithm (Keilies-Borko and Kossobokov, 1987) recognizes the time of increased probability, TIP, for an earthquake with magnitude 7.0–7.5 from July 1991 through June 1996. The prediction is limited to a circle of 280-km radius centered at 33.5°N, 133.75°E. The broad area of intermediate-term precursory rise of activity encompasses a 175 by 175-km square, where the sequence of earthquakes exhibited a specific intermittent behavior. The square is outlined as the second-approximation reduced area of alarm by the "Mendocino Scenario" algorithm, MSc (Kossobokov et al., 1990). Moreover, since the M8 alarm starts, there were no swarms recorded except the one on 9–26 Nov. 1994, located at 34.9°N, 135.4°E. Time, location, and magnitude of the 1995 Kobe earthquake fulfill the M8-MSc predictions. Its aftershock zone ruptured the 54-km segment of the fault zone marked by the swarm, directly in the corner of the reduced alarm area. The Kobe 1995 epicenter is less than 50 km from the swarm and it coincides with the epicenter of the M 3.5 foreshock which took place 11 hours in advance.     

Revisiting the Basin-edge Effect at Kobe During the 1995 Hyogo-Ken Nanbu Earthquake

The basin edge effect, i.e., the interference of the direct S wave with the surface wave diffracted off the basin edge has been invoked by many authors to explain the damage distribution during the January 17, 1995 Hyogo-Ken Nanbu (Kobe) earthquake. Here we present the results of numerical experiments obtained with the spectral element method in 2-D geometry. Our results confirm that the amplification of horizontal motion close to the basin edge can be twice as large as the one measured in the center of the basin. This additional amplification is shown to depend strongly on the edge geometry and on frequency, due to physical dispersion of diffracted surface waves. In particular we obtain maximal amplification around 3 Hz, at frequencies critical for buildings.     

Research on the seismotectonics of the Jan－uary 17，1995 Hanshin M7．2 earthquake

ＲｅｓｅａｒｃｈｏｎｔｈｅｓｅｉｓｍｏｔｅｃｔｏｎｉｃｓｏｆｔｈｅＪａｎ┐ｕａｒｙ１７，１９９５ＨａｎｓｈｉｎＭ７．２ｅａｒｔｈｑｕａｋｅＺＨＵ－ＪＵＮＨＡＮ１）（韩竹君），ＦＵ－ＨＵＲＥＮ２）（任伏虎），ＹｕｊｉｒｏＯｇａｗａ２）（小川雄二郎）ａ...     

Subaqueous sand blow deposits induced by the 1995 Hyogo-ken Nanbu Earthquake, Japan

Abstract The 1995 Hyogo-ken Nanbu Earthquake (Mw 6.9) occurred in the region around Kobe City and Awaji Island in south-west Japan. Co-seismic liquefaction caused subsidence of the land and damage to sea wall caissons on the man-made Port Island at Kobe City. A zone 2–3 m wide behind the caissons of the northern wharf on the island subsided into the intertidal zone and a sandy deposit settled into this subsided zone. The depos-it consists of upward-fining sequences that are subdivided into three parts, in ascending order: graded coarse- to medium-grained sand, parallel-laminated fine- to very-fine-grained sand, and massive mud. Grain fabric analysis (employing the anisotropy of magnetic susceptibility method and microscopic measurement) of these sequences shows that there is a remarkable contrast in grain fabric between the lowest portion of the graded sand division and the laminated sand division. The former has a high q -value (magnetic lineation/foliation) and a unimodal orientation of elongate grains in the horizontal plane, but random orientation in the vertical plane. Conversely, the latter is characterized by a low q -value and a grain fabric in which the long axes of the grains have random orientations and are nearly parallel to the plane of deposition. This result shows that the main depositional processes changed from a combination of flow and allied processes to the force of gravity. As still water is essential for gravity to be the dominant factor in deposition, this deposit is regarded as subaqueous sand blow deposits. If this interpretation is correct, the grain fabric produced by gravity alone is a useful criterion for distinguishing between subaqueous sand blow deposits and other liquefaction-induced deposits.     

Research on the seismotectonics of the January 17, 1995 HanshinM7.2 earthquake

Based on the geological tectonics, aftershock activity, earthquake surface rupture and peak ground motion, the geometric and dynamic characteristics of seismogenic tectonics about the 1995 Hanshin earthquake are analysed. Nojima fault and Rokko fault have the same trending direction, but opposite dips. Their rising and falling plates are in symmetrically diagonal distribution. The two faults can be defined as thrust-strike slip faults and constitute a pivotal strike-slip fault. The earthquake just occurred at the pivot, which is the seismotectonics for the earthquake to develop and occur. The pivotal movement along a strike-slip fault often leads to the occurrence of large earthquakes, whose dynamic process can be demonstrated by the stress analysis on the torsion of a beam with rectangle section. The displacement of earthquake surface rupture, aftershock density and peak acceleration change in a certain range of epicentral distance just similar as the shear stress changes from the center to the sides in the rectangle section. The distribution characteristics of the heaviest damage areas are also discussed in the article from the aspects of special geological tectonics and seismotectonic condition. The result obtained from the article can be applied not only to realizing the potencial earthquake sources in middle-long time, but also to build reasonably the prediction model about earthquake hazard.     

Verification of predicted non-linear site response during the 1995 Hyogo-Ken Nanbu earthquake

The linear and non-linear responses of surface soil layers have been predicted through the simultaneous simulation test against the observed ground motions at the six sites in Kobe City during the 1995 Hyogo-ken Nanbu earthquake. The total stress analysis method and the effective stress analysis method have been applied for the rough and detailed verification of the predicted non-linear dynamic behavior at the PIS and RKI sites including the liquefaction phenomenon. The shear strain distribution along depth, the ratio of excess pore water pressure to initial effective stress, the liquefaction strength parameters to initial effective stress, and the stress–strain curve during the earthquake at the PIS site have been investigated when the predicted ground motion could simulate successfully the observed acceleration time histories and response spectra in the non-linear range.     

2001年1月26日印度7.7级地震

20 0 1年 1月 2 6日 ,印度西部发生一次大地震 ,当时正值印度全国庆祝共和日。这次地震对独立的印度来说 ,无疑是一次破坏极其惨重的地震。自地震发生后 ,救援人员一直在努力清理废墟 ,并从倒塌的瓦砾中救出可能的幸存者。政府也已承认这次地震给印度造成的损失惨重。科学家们认为 ,过去没有对这一地区进行过全面的研究 ,最近几年才开始对该地区的古地震活动性进行了一些研究。其中一项研究是在卡奇沼泽地进行卡奇地区的地震历史研究。这里有一份关于卡奇地震带形变特征的详细报告的摘要。 1 81 9年发生在印度西北部的卡奇地震 ,是最显著的…     

Research on the seismotectonics of the January 17, 1995 Hanshin M 7.2 earthquake

Based on the geological tectonics, aftershock activity, earthquake surface rupture and peak ground motion, the geometric and dynamic characteristics of seismogenic tectonics about the 1995 Hanshin earthquake are analysed. Nojima fault and Rokko fault have the same trending direction, but opposite dips. Their rising and falling plates are in symmetrically diagonal distribution. The two faults can be defined as thrust-strike slip faults and constitute a pivotal strike-slip fault. The earthquake just occurred at the pivot, which is the seismotectonics for the earthquake to develop and occur. The pivotal movement along a strike-slip fault often leads to the occurrence of large earthquakes, whose dynamic process can be demonstrated by the stress analysis on the torsion of a beam with rectangle section. The displacement of earthquake surface rupture, aftershock density and peak acceleration change in a certain range of epicentral distance just similar as the shear stress changes from the center to the sides in the rectangle section. The distribution characteristics of the heaviest damage areas are also discussed in the article from the aspects of special geological tectonics and seismotectonic condition. The result obtained from the article can be applied not only to realizing the potencial earthquake sources in middle-long time, but also to build reasonably the prediction model about earthquake hazard.