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Wan Yongge 《中国地震研究》2007,21(1):33-42
The influences upon aftershocks of Coulomb failure stress change (CFSC) generated by the main-shock of the October 8, 2005, Pakistan earthquake are calculated and analyzed. The following factors are included in the calculation: (1) the difference between the pore fluid pressure and the medium elastic constant in the fault plane area and those of its surrounding medium; (2) the tectonic stress direction of the seismic source area; (3) the aftershock failure mechanism of aftershocks is calculated by stacking the tectonic stress with the stress change generated by the main-shock. Our study, which includes many factors, fits fairly well with the aftershock distribution. It indicates that most of the aftershocks were triggered by the Pakistan main-shock that occurred on October 8, 2005. 相似文献
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据中国台网测定,2005年10月8日11时50分36.0秒(当地时间10月8日上午8时50分),在巴基斯坦(34.4°N,73.6°E)发生7.8级地震。巴基斯坦首都伊斯兰堡有明显震感。震中位于巴控克什米尔地区,并波及邻近印度控制的克什米尔地区和阿富汗。震中距巴基斯坦首都伊斯兰堡95 km,距印控克什米尔地区首府斯利那加125 km,震源位于地下10 km处。除了印控克什米尔地区以外,印度旁遮普邦、喜马偕尔邦、哈里亚纳邦、中央邦、古吉拉特邦、首都新德里等地区均有不同程度的震感。地震发生后,巴基斯坦总统穆沙拉夫说,这场强烈地震是对巴基斯坦全体人民的考验。巴基… 相似文献
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Geotechnical evaluation of slope and ground failures during the 8 October 2005 Muzaffarabad earthquake, Pakistan 总被引:4,自引:0,他引:4
A large devastating earthquake with a magnitude of 7.6 struck in Kashmir on Oct. 8, 2005. The largest city influenced by the
earthquake was Muzaffarabad. Balakot town was the nearest settlement to the epicenter, and it was the most heavily damaged.
The earthquake caused extensive damage to housing and structures founded on loose deposits or weathered/sheared rock masses.
Furthermore, extensive slope failures occurred along Neelum and Jhelum valleys, which obstructed both river flow and roadways.
In this article, failures of natural and cut slopes as well as other ground failures induced by the earthquake and their geotechnical
evaluation are presented, and their implications on civil infrastructures and site selection for reconstruction and rehabilitation
are discussed. It is suggested that if housing and constructions on soil slopes containing boulders as observed in Balakot
and Muzaffarabad are allowed, there should be a safety zone between the slope crest and allowable construction boundary. 相似文献
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巴基斯坦曼塞赫拉7.8级地震对中国大陆大震趋势影响的初步研究 总被引:1,自引:0,他引:1
讨论了喜马拉雅弧型地震构造带西反射弧地带(简称“西触角区”),大地震活动的基本特征及2005年10月巴基斯坦曼塞赫拉7.8级地震发生后,对中国大陆地震趋势的可能影响。西触角区(N30~45°,E61~80°)大震活动存在显著的时间上10年左右成组性及两次大震时间间隔小于1个月的爆发性,地点上的成丛性,兴都库什深震区的地震有一定先兆意义,与东触角区(N20~29°,E95~102°)大地震也存在较好的相关性。沿欧亚大陆与印度洋、澳州板块碰撞带上印尼苏门答腊8.9级地震后,再次发生巴基斯坦7.8级大地震,显示出这一板缘地震带正处于活跃状态。研究认为未来1~2年应注意西触角区尤其是天山地震带的大震连发的危险性及东触角区(缅甸及川、滇为主)发生响应性大地震的可能性。对中国大陆内部其他地区大震形势的影响可能不大。 相似文献
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自2002年9月起,在阿格拉布设了由三分量感应式磁力仪(f=0.01~30Hz)组成的观测系统,监测与地震有关的超低频磁场辐射信息。大量的数据显示,正常情况下,三分量(Bx,By,Bz依次代表的方向是北南、东西和垂直向)的振幅都比较低,在0.01-0.3nT之间。偶尔也会发现By和Bz分量增强到0.3~2nT的现象(Bx分量最小)。这种增强大多对应地震的发生,By和Bz分量信号的增强分别对应阿格拉的东北(或南北)和西北方向的地震。不久前,就发现了Bz分量的增强与2005年10月8日发生在阿格拉西北900km的穆扎法拉巴德(巴基斯坦)大地震(M=7.7)之间存在这种对应关系。经研究2005年10月整月期间发生的太阳耀斑和磁暴,发现幅度增强与这些事件负相关。这就得到一个令人感兴趣的结果:这种幅度的增强是地震前兆现象,该前兆现象首先出现在震前约10天的9月27~30日,其次出现在震前的前3天,即2005年10月5日。通过对2005年9月17~10月29日之间的数据进行前后15天的平均(m)和标准偏差(m±2a)统计分析,可以证实这种信号是地震前兆信号。前兆信号强度上的增强,还可以从数据的小波分析结果中观察到。从数据的时频谱和功率谱分析显示信号增强发生在2Hz和7~8Hz,并且极化分析显示这是从下面传播而来的信号。 相似文献
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Geological setting of the 8 October 2005 Kashmir earthquake 总被引:1,自引:0,他引:1
The source of the 8 October 2005 earthquake of M 7.6 was the northwest-striking Balakot–Bagh (B–B) fault, which had been mapped by the Geological Survey of Pakistan prior
to the earthquake but had not been recognized as active except for a 16-km section near Muzaffarabad. The fault follows the
Indus–Kohistan Seismic Zone (IKSZ); both cut across and locally offset the Hazara–Kashmir Syntaxis defined by the Main Boundary
and Panjal thrusts. The fault has no expression in facies of the Miocene–Pleistocene Siwalik Group but does offset late Pleistocene
terrace surfaces in Pakistan-administered Jammu-Kashmir. Two en-échelon anticlines near Muzaffarabad and Balakot expose Precambrian
Muzaffarabad Limestone and are cut by the B–B fault on their southwest sides, suggesting that folding and exposure of Precambrian
rocks by erosion accompanied Quaternary displacement along the fault. The B–B fault has reverse separation, northeast side
up; uplift of the northeast side accompanied displacement, producing higher topography and steeper stream gradients northeast
of the fault. No surface expression of the B–B fault has been found northwest of the syntaxis, although the IKSZ and steeper
stream gradients continue at least as far as the Indus River, the site of the Pattan earthquake of M 6.2 in 1974. To the southeast, northwest-striking faults were mapped by the Geological Survey of Pakistan. One of these faults,
the Riasi thrust, cuts across the southwest flank of an anticline exposing Precambrian limestone. Farther southeast, in Indian-administered
territory, Holocene activity on the Riasi thrust has been described. In the Kangra reentrant still farther southeast, active
faulting may follow the Soan thrust, along which Holocene and Pleistocene offsets have been described. The Soan thrust, rather
than the south flank of the Janauri anticline, may represent the surface projection of the 1905 Kangra earthquake of M 7.8. 相似文献
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Prantik Mandal R. K. Chadha N. Kumar I. P. Raju C. Satyamurty 《Pure and Applied Geophysics》2007,164(11):2235-2254
During the last six years, the National Geophysical Research Institute, Hyderabad has established a semi-permanent seismological
network of 5 broadband seismographs and 10 accelerographs in the Kachchh seismic zone, Gujarat, with the prime objective to
monitor the continued aftershock activity of the 2001 Mw7.7 Bhuj mainshock. The reliable and accurate broadband data for the Mw 7.6 (8 Oct., 2005) Kashmir earthquake and its aftershocks from this network, as well as from the Hyderabad Geoscope station,
enabled us to estimate the group velocity dispersion characteristics and the one-dimensional regional shear-velocity structure
of peninsular India. Firstly, we measure Rayleigh- and Love-wave group velocity dispersion curves in the range of 8 to 35
sec and invert these curves to estimate the crustal and upper mantle structure below the western part of peninsular India.
Our best model suggests a two-layered crust: The upper crust is 13.8-km thick with a shear velocity (Vs) of 3.2 km/s; the
corresponding values for the lower crust are 24.9 km and 3.7 km/sec. The shear velocity for the upper mantle is found to be
4.65 km/sec. Based on this structure, we perform a moment tensor (MT) inversion of the bandpass (0.05–0.02 Hz) filtered seismograms
of the Kashmir earthquake. The best fit is obtained for a source located at a depth of 30 km, with a seismic moment, Mo, of
1.6 × 1027 dyne-cm, and a focal mechanism with strike 19.5°, dip 42°, and rake 167°. The long-period magnitude (MA ~ Mw) of this earthquake is estimated to be 7.31. An analysis of well-developed sPn and sSn regional crustal phases from the bandpassed
(0.02–0.25 Hz) seismograms of this earthquake at four stations in Kachchh suggests a focal depth of 30.8 km. 相似文献
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伽师强震群的深部动力学条件 总被引:3,自引:1,他引:3
根据天山造山带及其两侧的塔里木盆地和准噶尔盆地的岩石圈二维速度结构、二维密度结构、二维电性结构、壳幔过渡带的详细结构以及大地热流和震源深度的分布,再结合对新疆西北部的蛇绿岩带、高压变质带和岩浆岩分布的综合分析,建立了天山造山带的地球动力学“层间插入消减”模型。该模型认为,塔里木板块的中上地壳在库尔勒断裂附近向天山造山带的中下地壳层间插入;而下地壳连同岩石圈地幔向天山造山带的上地幔俯冲消减。在天山的西段(哈萨克斯坦境内),费尔干纳地块由北向南插入到南天山之下约180km的深处,在其东段(中国境内),塔里木盆地由南向北插入南天山之下。这两个具有不同方向的下降板片的接触部位为费尔干纳走滑断裂。我国的伽师、喀什、乌恰地震区均落在这两个具有不同俯冲方向板块的结合部位附近,有着特殊的深部构造背景。南、北两大板块的双向挤压必定产生强大的应力,在地震区附近,这种应力的积累与释放具有4个显著的特点:(1)板片的俯冲消减速度约高达每年22mm左右;(2)应力的积累与释放速率加快;(3)应力释放较容易;(4)应力释放较为集中。这4个特点可能是伽师地区在较短的时间内连续发生数次强震的构造因素。 相似文献
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Observations of damage due to the Kashmir earthquake of October 8, 2005 and study of current seismic provisions for buildings in Pakistan 总被引:2,自引:3,他引:2
On October 8, 2005 an earthquake of magnitude 7.6 (M
w) struck the Kashmir region of Pakistan causing widespread damage to buildings and infrastructure. This paper summarizes field
observations of building damage made by the Earthquake Engineering Field Investigation Team (EEFIT) after the event, where
the performance of residential, commercial and government buildings was investigated. A study of the seismic design provisions
currently in place in Pakistan is presented and compared with seismic provisions of EC8 (1998) and UBC (1997). Several problems
are identified for the implementation of the Pakistan seismic code in its current form and recommendations are made for its
improvement in order to be used for the reconstruction of affected areas. 相似文献
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Prantik Mandal R. K. Chadha N. Kumar I. P. Raju C. Satyamurty 《Pure and Applied Geophysics》2007,164(10):1963-1983
During the last six years, National Geophysical Research Institute, Hyderabad has established a semi-permanent seismological
network of 5–8 broadband seismographs and 10–20 accelerographs in the Kachchh seismic zone, Gujarat with a prime objective
to monitor the continued aftershock activity of the 2001 Mw 7.7 Bhuj mainshock. The reliable and accurate broadband data for the 8 October Mw 7.6 2005 Kashmir earthquake and its aftershocks from this network as well as Hyderabad Geoscope station enabled us to estimate
the group velocity dispersion characteristics and one-dimensional regional shear velocity structure of the Peninsular India.
Firstly, we measure Rayleigh-and Love-wave group velocity dispersion curves in the period range of 8 to 35 sec and invert
these curves to estimate the crustal and upper mantle structure below the western part of Peninsular India. Our best model
suggests a two-layered crust: The upper crust is 13.8 km thick with a shear velocity (Vs) of 3.2 km/s; the corresponding values
for the lower crust are 24.9 km and 3.7 km/sec. The shear velocity for the upper mantle is found to be 4.65 km/sec. Based
on this structure, we perform a moment tensor (MT) inversion of the bandpass (0.05–0.02 Hz) filtered seismograms of the Kashmir
earthquake. The best fit is obtained for a source located at a depth of 30 km, with a seismic moment, Mo, of 1.6 × 1027 dyne-cm, and a focal mechanism with strike 19.5°, dip 42°, and rake 167°. The long-period magnitude (MA ~ Mw) of this earthquake is estimated to be 7.31. An analysis of well-developed sPn and sSn regional crustal phases from the bandpassed
(0.02–0.25 Hz) seismograms of this earthquake at four stations in Kachchh suggests a focal depth of 30.8 km. 相似文献
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Located on the east boundary of Qinghai-Xizang (Tibet) Plateau, the M_S8.0 Wenchuan earthquake is the strongest event to hit the active block since the 2001 Kunlun Mountains Pass earthquake. In this study, a simplified source model of the Wenchuan earthquake is constructed based on the deep/shallow tectonic settings and crust/mantle structure features of the Longmenshan thrust fault zone. On the basis of dynamic model abstraction, we construct a system of dynamical equations for the seismogenic process and obtain the analytical expressions of stress and strain in the seismogenic process. A preliminary study of the seismogenic process of the M_S8.0 Wenchuan earthquake, based on the analytical solution of the model and observation of tectonic deformation in the Longmenshan region, indicates that the seismogenic process of the Wenchuan earthquake took place over a period of more than 3200 years. The slow process of seismogeny and the long recurrence period of strong earthquakes are attributed to the low deformation rate of the Longmenshan tectonic zone. 相似文献
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汶川8.0级地震构造动力成因分析 总被引:9,自引:1,他引:9
汶川8.0级地震发生在青藏活动地块区的东部边界带, 是继2001年昆仑山口西大地震之后青藏块区的又一次巨大地震。 根据龙门山推覆逆冲断裂带深浅部构造背景和壳幔结构特征, 文中构建了汶川地震的震源简化模型。 并依据震源模型的力学抽象建立了孕震过程的动力学方程组, 且在简化解释下给出了孕震过程中的应力、 应变的解析表达式。 应用模型的解析解, 并参照龙门山构造区的构造形变观测结果, 初步讨论了汶川地震的孕震过程, 给出了汶川8.0级地震的孕育过程可达3000多年的结果, 指出由于龙门山地区构造形变速率很低, 因而导致孕震过程缓慢, 大震复发期较长的基本结果。 相似文献
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Relaxation of the coseismic stresses following an earthquake causes postseismic crustal deformation, which can last for days
to years. Continuous monitoring of postseismic deformation facilitates the understanding of the mechanism of deformation and
postseismic relaxation and viscous rheology. After the October 8, 2005 Kashmir earthquake, global positioning system data
for 8 months, starting from October, 2005 have been analyzed from three continuous sites located at Gulmarg, Amritsar, and
Jaipur. The average velocity during the observation period at Gulmarg (8.6 cm/year) is significantly higher than the Indian
plate velocity exhibiting postseismic crustal deformation. The velocity at Amritsar (5.9 cm/year) and Jaipur (5.1 cm/year)
is comparable to the Indian plate velocity. At Gulmarg, the logarithmic function fits well to the north–south component of
postseismic transients (~in the coseismic slip direction). The nature of decay in these transients suggests that the deformation
is mainly due to an afterslip, and the second possible contribution may be from the viscous relaxation process. This paper
presents the characteristics of postseismic transients and possible contributions from various postseismic mechanisms subsequent
to the Kashmir earthquake. 相似文献
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华北地区与青藏高原地区强震孕育过程相关性的动力学解释 总被引:1,自引:0,他引:1
根据不同学者对中国应力场的研究结果,普遍认为中国大陆板内构造变形活动的主要驱动力源来自印度板块与欧亚大陆的碰撞挤压作用,两大板块的汇聚作用主要发生在喜马拉雅碰撞带和帕米尔碰撞带,欧亚板块在这一碰撞带承受了印度板块的强烈挤压作用。全国GPS地壳运动观测结果也证明了以上的研究结论,基于国家攀登计划建立的全国GPS网21点的复测结果, 相似文献
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The Muzaffarabad region in western Himalaya, the site of the devastating earthquake of 8 October 2005 of magnitude 7.6, occupies
a unique tectonic position, encompassed by the Himalayan arc to the east and the complex thrust zones of Pamir and Hindukush
in the north and northwest respectively. Further, the region is entangled in a peculiar overturned syntaxial bend of the Main
Central Thrust (MCT), north of Main Boundary Thrust (MBT). A study of focal mechanisms and stress inversion in each of these
regions indicates varied stress regimes demonstrating their distinct tectonic character. While shallow plane thrust faulting
with low dip angles is generally witnessed along the Himalayan arc, a transition to steep fault plane dips up to 45° is seen
in the Muzaffarabad region on the western side. It is inferred that the stress field in Muzaffarabad region is not a mere
extension of that in the Himalayan arc but is controlled by the complex interplay of the surrounding diverse tectonic structural
units comprising the Himalaya, Hindukush and Pamir, rather than merely the tectonic forces of India–Eurasia collision. 相似文献