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991.
论汶川8.0级地震前的地震活动及趋势估计问题 总被引:1,自引:1,他引:0
本文对汶川8.0级地震前南北地震带大震轮回、首发大震、地震平静或空区、地震条带等地震活动图像在震前分析的基础上就地震预测问题进行了思考。地震活动图像在蕴震过程或阶段的估计只能是背景或中期预测的意义。同时指出区域地震活动图像在大范围多构造区的蕴震态分析中的复杂性。 相似文献
992.
通过对2008年5月12日四川汶川8级地震与地球自转关系的分析,提出了一个新的地震成因观点,认为地震的根本原因在于地球自转速率的变化。地球岩石圈由大小不同、质量不同的块体组成。比如,大洋块体薄、质量轻,大陆块体厚、质量重。地球自转速率变化时,就会造成这些块体运动的差异性。这种差异运动可能使块体之间发生“追尾”撞击或摩擦,从而引起地震。地震能量来自于块体间撞击或摩擦时损失的动能。 相似文献
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995.
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
996.
The great M_S8.0 Wenchuan earthquake on May 12,2008 was generated by abrupt faulting in the Yingxiu-Beichuan fault along the Longmenshan fault zone. The earthquake not only produced surface ruptures along the Yingxiu-Beichuan and Guanxian-Jiangyou faults,but also surface ruptures,arching of highway pavement,sand-boils and waterspouts in various degrees in areas such as Shifang and Mianzhu on the Chengdu Plain. To understand the shallow geological structures under the surface rupture zone,a 6350m long high-resolution shallow seismic reflection profile in near-EW direction was performed. This profile is located at Shigu town,Shifang city,where a suspected earthquake surface rupture zone was discovered. In this study,a group interval of 3m,shotpoint interval of 18m,and a 300-channel 25-fold observation system were used. In consideration of both near-surface reflections and dipping interface imaging,we adopted the split-spread geometry and asymmetrical zero-offset receiving technique. To better suppress random-noise and raise the signal-to-noise ratio of seismic data,30 times vertical stacking of vibrator signals was made for each common-shot gather after correlation of individual records. By using the above work method and spread geometry,we obtained high-resolution images of structures in the depth range of 15m~800m after data processing. The result shows the existence of buried thrust faults thrusting to the plain area and back-thrust faults under the surface rupture zone. It also shows that the activity of the buried thrust faults may be the main cause for folding and deformation in near-surface strata and coseismic surface rupturing. 相似文献
997.
通过对汶川8.0级地震的类型和破裂特征分析, 讨论了龙门山构造带地震活动与甘肃省地震活动的关系.回顾了对汶川地震序列的动态跟踪过程以及余震活动在甘肃省的震情判定过程.认为地震预报应从地震的孕育、发展和发生过程中获得更多的物理信息,改变以往以经验、统计预报为主的模式,向以物理预报为主的预报模式迈进. 相似文献
998.
面向对象遥感分类方法在汶川地震震害提取中的应用 总被引:7,自引:0,他引:7
震后城市建筑物震害的自动识别与分类, 是遥感震害调查中的关键步骤, 其精度直接影响损失评估的结果. 而随着高分辨率遥感影像的发展, 传统基于像元的分类技术已不能满足需求, 引入面向对象的信息提取技术, 充分挖掘影像对象的纹理、形状和相互关系等信息, 能够有效的提高震害的分类精度. 该文阐述了面向对象的遥感震害提取思路和方法, 并应用汶川地震震后高分辨率航空遥感数据, 针对建筑物震害进行面向对象的快速提取与自动分类. 结果表明, 与基于像元分类比较, 面向对象的建筑物震害分类能够显著改善分类效果. 相似文献
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1000.
Hai?Lou ChunYong?WangEmail author ZhiYong?Lü ZhiXiang?Yao ShiGu?Dai HuiChuan?You 《中国科学D辑(英文版)》2009,52(2):166-179
Teleseismic P-wave receiver functions at 20 broadband seismic stations in the Longmenshan fault zone (LMFZ) and its vicinity
were extracted, and the crustal thickness and the P- and S-wave velocity ratio were calculated by use of the H-k stacking algorithm. With the results as constraints, the S-wave velocity structures beneath each station were determined
by the inversion of receiver functions. The crustal structure of the Rear-range zone is similar to that of the Songpan-Garze
Block, whereas the velocity structure of the Fore-range zone resembles that of Sichuan Basin, implying that the Central Principal
Fault of LMFZ is the boundary between the eastern Tibetan Plateau and the Yangtze Block. Lower velocity zone exists in lower
crust of the Songpan-Garze Block and the central-southern segment of the Rear-range zone, which facilitates the detachment
of the material in upper and middle crust. Joint analysis of the receiver functions and the Bouguer gravity anomalies supports
the thesis on the detachment-thrust mode of the LMFZ. A double-detachment pattern is suggested to the tectonic setting in
the Songpan-Garze Block. The upper detachment occurs at the depth of 10-15 km, and represents a high-temperature ductile shear
zone. There is a lower detachment at the depth of about 30 km, below which the lower crust flow exists in the eastern Tibetan
Plateau. Interpretation of the Bouguer gravity anomalies indicates that the Sichuan Basin is of higher density in upper and
middle crust in comparison with that of the Songpan-Garze Block. The LMFZ with higher density is the result from the thrusting
of the Songpan-Garze Block over the Sichuan Basin. In the lower crust, higher P velocity and higher density in the Sichuan
Basin are related to more rigid material, while lower S velocity and lower density in the Songpan-Garze Block are related
to the softened and weakened material. The higher density block beneath the Sichuan Basin obstructs the eastward flow of lower
crustal material from the Tibetan Plateau, which is driven by the compression of northward movement of Indian Plate. The eastward
movement of upper and middle crustal material is also obstructed by the rigid Yangtze Block, resulting in the stress concentrated
and accumulated along the LMFZ. When the stress releases sharply, the Wenchuan M
s8.0 earthquake occurs.
Supported by the National Natural Science Foundation of China (Grant Nos. 40334041, 40774037) and Joint Foundation of Earthquake
Science (Grant No. 1040062) 相似文献