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汶川5月12日8.0级地震在构造上起因于印度板块与欧亚板块以每年约5 cm的速度聚敛,并因此而引起青藏高原的地壳物质向四川盆地及中国东南大陆运移.主震震源及余震活动集中于以龙门山为中轴的一条长约350 km、宽约100 km的地震活动带.震源深度一般分布丁地壳脆性-韧性转换边界以上约10~20 km区间的地壳震源层之中,属浅源构造地震.主要震源机制与龙门山构造运动方式密切相关,以其地壳厚度向西急剧加厚、重力梯度带、高波速比(Vp/Vs~2.2)等深部异常及逆冲断层兼具走滑性质的地质构造为特征.在震源辐射、路径传播和场地效应研究的基础上,分别计算并比较了岩石和土壤条件下的地震响应谱,特别强调了土壤条件下的场地放大效应;同时对与地震安全性有关的一些问题如地质灾害、地震频谱设计、地震早期预警系统及中、长期至短期地震预报等进行了探讨;特别提供了一个由加权平均计算、以岩石条件下震波衰减模式为基础的地震频谱设计参考实例.地震构造与动力学研究可融人工程地质与环境工程等学科发展.经历汶川地震考验的一些新近设计和建设的工程项目可为今后改进工程建筑规范与标准提供重要而有益的参考.地震预报是当今一大难题,但需探索研究,不可懈怠.地震减灾与预防足目前比较切合实际的安全举措. 相似文献
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汶川大震的科学思考 总被引:1,自引:0,他引:1
在野外地震地质科学考察的基础上,围绕汶川地震发震断层的特征、发震机制、地表破裂带的分段性与分带性、南北构造带地震危险性、地震地质灾害的多发性及链生性、工程建(构)筑物的破坏特征与安全性、地震烈度区划问题及极端自然灾害的预测与应对等进行了分析和讨论,并就有关问题提出了一些新的思考。结果表明,低速滑动断层、晚更新世断层或中央活动断裂也可以发生强震;汶川地震同时具有深部构造的控震作用;地表破裂沿走向可分为映秀—安县段、北川—关口段及青川段;地表破裂可分为主破裂、牵动破裂与感应破裂3种类型;青川段的深部破裂与浅部破裂没有几何上的连续关系或继承关系;贺兰—川滇南北构造带是中国大陆强震多发带,尤其是其北段的六盘山—天水—武都—青川一带未来的强震危险性不容忽视;汶川地震地质灾害具有灾害类型多、成因机理复杂、灾害链长、规模大、范围广、灾害程度深、危害对象广、持续时间长等特点;高烈度区和活断层沿线的地质灾害危险性区划与预测评价对防灾减灾极为重要;活动断裂沿线应注意破裂影响带宽度与建筑物安全避让距离;应对地震等极端自然灾害,应以预防为主,综合减灾;地震烈度区划应同时考虑活动断层的复发周期、地震的离逝时间乃至地形地貌条件;重大工程应提高设防烈度;应当加强极端自然灾害预测评估,完善应对对策和提高应对水平。 相似文献
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<正>The energy transformation and efficiency is now a hot topic among researches of scientific drilling into fault zones(Tanaka et al.,2006;Ma et al.,2006).This study conducted temperature measurements and fault gouge particle analysis of borehole WFSD-1 from the Wenchuan Earthquake Fault Science Drilling Project(WFSD),and discussed the earthquake energy budget.The research progress is illuminated as follows.Through collection and analysis of source time function for the Wenchuan earthquake,this study used triangular 相似文献
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ZHANG Fawang ZHANG Zhaoji HAN Zhantao SUN Jianping XIAO Guoqiang Institute of Hydrogeology Environmental Geology Chinese Academy of Geological Sciences Zhengding China Center of Hydrogeology Environmental Geology China Geology Survey Baoding China Tianjin Center of China Geology Survey Tianjin China 《《地质学报》英文版》2009,83(4)
This paper introduced the first hand investigation results of the risk and treatment measures for the barrier lakes triggered by the earthquake of Wenchuan.Characteristics of 10 barrier lakes were investigated and analyzed;procedure and methods for barrier lake treatment were brought forward.The dams of the barrier lakes can be classified as two classes:block rock in the south and loose deposit in the north.All the barrier dams were stable at the time of investigation,but water drainage channel needed to... 相似文献
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Peng Cui Chao Dang Jian-qi Zhuang Yong You Xiao-qing Chen Kevin M. Scott 《Environmental Earth Sciences》2012,65(4):1055-1065
Landslides and rock avalanches triggered by the 2008 Wenchuan Earthquake produced 257 landslide dams, mainly situated along
the eastern boundary of the Qinghai-Tibet Plateau where rivers descend approximately 3,000 m into the Sichuan Basin. The largest
of these dams blocked the Tongkou River (a tributary of the Fujiang River) at Tangjiashan. The blockage, consisting of 2.04 × 107 m3 of landslide debris, impounded a lake with a projected maximum volume of 3.15 × 108 m3, potentially inundating 8.92 km2 of terrain. Its creation during the rainy season and the possibility of an uncontrolled release posed a serious, impending
threat to at least 1.3 million people downstream that could add substantially to the total of 69,200 individuals directly
killed by the earthquake. Risk assessment of the blockage indicated that it was unlikely to collapse suddenly, and that eventual
overtopping could be mitigated by notching the structure in order to create an engineered breach and achieve safe drainage
of the lake. In addition to the installation of monitoring and warning instrumentation, for emergency planning we estimated
several outburst scenarios equivalent to 20, 25, 33, and 50% of the dam failing suddenly, creating, respectively, 3.35, 3.84,
4.22, and 4.65 km2 of flooded area, and overbank water depths of 4.6, 5.1, 5.7, and 6.2 m, respectively, in Mianyang, the second largest city
in Sichuan Province, 48 km downstream from the blockage. Based on these scenarios, recommendations and plans for excavating
a sluiceway, draining the lake, and downstream evacuation were proposed and later were implemented successfully, with the
blockage breached by overtopping on June 10, less than a month after dam emplacement. The peak discharge of the release only
slightly exceeded the flood of record at Mianyang City. No lives were lost, and significant property damage was avoided. Post-breaching
evaluation reveals how future similar mitigation can be improved. Although initial breach erosion was slow, later erosion
was judged uncontrollably rapid; increased slope of the engineered channel and adoption of a compound, trapezoid–triangular
cross-section can be considered, as can other measures to control the rate of breach incision. Evacuees from Mianyang City
spent an unnecessarily long time (12 days) in temporary settlements; more precise risk management planning can reduce this
time in the future. 相似文献
8.
Emergency response to the Tangjiashan landslide-dammed lake resulting from the 2008 Wenchuan Earthquake, China 总被引:1,自引:1,他引:0
Natural landslide dams triggered by earthquakes are a common feature and a significant hazard in high-relief, tectonically
active areas. The great Wenchuan Earthquake of May 12, 2008 created 256 natural dams, of which 34 presented significant risks
to downstream areas in the event of their uncontrolled failure. Out of the 34 large landslide dams that warranted mitigation,
we discuss Tangjiashan landslide dam in detail. Emergency response to the Tangjiashan landslide-dammed lake in the following
weeks and months successfully reduced the risk, and the advantages and disadvantages of various countermeasures that were
applied are summarized here. Successful strategies relied on accurate scientific assessments, on timely execution of the countermeasures,
and on the correct design of sluiceway (spillway) channels across the landslide dams. Retrospective assessment indicates that
the following improvements would be more beneficial: (1) Sluiceway channels utilizing a combination of cross-section types,
rather than simply trapezoidal in shape; (2) increased channel slope, which is more than the original gradient of the river;
(3) better protection of inlets and outlets to control the planned incision rates; and (4) channels lined to better control
the incision rate. We discuss applications of the concept of artificially controlled failure, and we submit these observations
for the benefit of those responding to future seismic catastrophes. 相似文献
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四川汶川Ms 8.0地震地表破裂构造初步调查与发震背景分析 总被引:19,自引:3,他引:19
5月16-24日对川西汶川大地震震中区的发震断裂地带进行的实地考察和初步测量,获得了宝贵的地表变形和同震位移最数据资料,证实汶川地震属于逆冲断裂型地震,主破裂沿映秀-北川断裂带发育,前山地区滑灌县-安县断裂也有地表破裂,同震位移量在3~5m.汶川地震产牛的地表破裂构造和运动性质显示明显分段特性,映秀-北川段以挤压逆冲为主,而北川以北段则伴有显著的右旋走滑分量. 相似文献
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DONG Shuwen ZHANG Yueqiao WU Zhenhan YANG Nong MA Yinsheng SHI Wei CHEN Zhengle LONG Changxing AN Meijian 《《地质学报》英文版》2008,82(5):938-948
An earthquake of Ms 8 struck Wenchuan County, western Sichuan, China, on May 12^th, 2008 and resulted in long surface ruptures (〉300 km). The first-hand observations about the surface ruptures produced by the earthquake in the worst-hit areas of Yingxiu, Beichuan and Qingchuan, ascertained that the causative structure of the earthquake was in the central fault zones of the Longmenshan tectonic belt. Average co-seismic vertical displacements along the individual fault of the Yingxiu-Beiehuan rupture zone reach 2.514 m and the cumulative vertical displacements across the central and frontal Longmenshan fault belt is about 5-6 m. The surface rupture strength was reduced from north of Beichuan to Qingchuan County and shows 2-3 m dextral strike-slip component. The Wenchuan thrust-faulting earthquake is a manifestation of eastward growth of the Tibetan Plateau under the action of continuous convergence of the Indian and Eurasian continents. 相似文献
11.
Over a period of 5 years, two large earthquakes struck Sichuan Wenchuan and Lushan successively. The two main seismic zones are only 87 km apart along the same seismic belt on the Longmenshan fault. Although there was only one magnitude of difference between the two great quakes, losses from the 2013 Lushan Earthquake were much lower than that of 2008 Wenchuan Earthquake. This study compares these disasters in terms of preparation and response in order to develop effective ways to reduce casualty and economic loss in future earthquakes. By determining what was done right after the Wenchuan Earthquake, we can better understand how to reduce future losses. This study focuses on seven factors: basic information, preparedness, government response, local residents’ responses, medical rescue teams’ work, earthquake-induced secondary effects, and injury character. We also recommend that three major actions should be emphasized to facilitate the most effective course of disaster planning and action. First, sufficient preparedness and strict preventive measures form the foundation to minimize damage and reduce casualties. Once the disaster had occurred, a single, well-run headquarters increases efficiency in rescue efforts. Finally, local rescue strength of both professional staff and citizens is the most critical factor to lower disaster casualties. 相似文献
12.
DONG Shuwen ZHANG Yueqiao WU Zhenhan YANG Nong MA Yinsheng SHI Wei CHEN Zhengle LONG Changxing AN Meijian 《《地质学报》英文版》2008,82(5)
An earthquake of Ms 8 struck Wenchuan County,western Sichuan,China,on May 12~(th), 2008 and resulted in long surface ruptures (>300 km).The first-hand observations about the surface ruptures produced by the earthquake in the worst-hit areas of Yingxiu,Beichuan and Qingchuan, ascertained that the causative structure of the earthquake was in the central fault zones of the Longmenshan tectonic belt.Average co-seismic vertical displacements along the individual fault of the Yingxiu-Beichuan rupture zone reach 2.5-4m and the cumulative vertical displacements across the central and frontal Longmenshan fault belt is about 5-6 m.The surface rupture strength was reduced from north of Beichuan to Qingchuan County and shows 2-3 m dextral strike-slip component.The Wenchuan thrust-faulting earthquake is a manifestation of eastward growth of the Tibetan Plateau under the action of continuous convergence of the Indian and Eurasian continents. 相似文献
13.
Abstract: This paper introduced the first hand investigation results of the risk and treatment measures for the barrier lakes triggered by the earthquake of Wenchuan. Characteristics of 10 barrier lakes were investigated and analyzed; procedure and methods for barrier lake treatment were brought forward. The dams of the barrier lakes can be classified as two classes: block rock in the south and loose deposit in the north. All the barrier dams were stable at the time of investigation, but water drainage channel needed to be constructed and to be protected from blockage or collapse. After the rain season of 2008, some dams needed to be consolidated, and change the barrier lakes to reservoirs. 相似文献
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The 12 May 2008 M7.9 Wenchuan earthquake in the People’s Republic of China represented a unique opportunity for the international
community to use commonly available GIS (Geographic Information System) tools, like Google Earth (GE), to rapidly evaluate
and assess landslide hazards triggered by the destructive earthquake and its aftershocks. In order to map earthquake-triggered
landslides, we provide details on the applicability and limitations of publicly available 3-day-post- and pre-earthquake imagery
provided by GE from the FORMOSAT-2 (formerly ROCSAT-2; Republic of China Satellite 2). We interpreted landslides on the 8-m-resolution
FORMOSAT-2 image by GE; as a result, 257 large landslides were mapped with the highest concentration along the Beichuan fault.
An estimated density of 0.3 landslides/km2 represents a minimum bound on density given the resolution of available imagery; higher resolution data would have identified
more landslides. This is a preliminary study, and further study is needed to understand the landslide characteristics in detail.
Although it is best to obtain landslide locations and measurements from satellite imagery having high resolution, it was found
that GE is an effective and rapid reconnaissance tool. 相似文献
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The Longmen Shan fault zone is located at the particular boundary between the Triassic Songpan-Ganzi orogen of the Qinghai-Tibetan Plateau and the stable Sichuan basin of the Yangtze platform. There are four major active faults and three tectonic nappes in this region. According to an analysis of neotectonics and historical earthquakes, the Longmen Shan fault zone presents a high level of seismic hazard. The rupture system that hosted the Wenchuan earthquake is characterized by thrust and dextral strike-slip movement. 相似文献
18.
Seismogenic Structure around the Epicenter of the May 12, 2008 Wenchuan Earthquake from Micro‐seismic Tomography 总被引:1,自引:0,他引:1
AN Meijian FENG Mei DONG Shuwen LONG Changxing ZHAO Yue YANG Nong ZHAO Wenjin ZHANG Jizhong 《《地质学报》英文版》2009,83(4):724-732
Abstract: A three-dimensional local-scale P-velocity model down to 25 km depth around the main shock epicenter region was constructed using 83821 event-to-receiver seismic rays from 5856 aftershocks recorded by a newly deployed temporary seismic network. Checkerboard tests show that our tomographic model has lateral and vertical resolution of ~2 km. The high-resolution P-velocity model revealed interesting structures in the seismogenic layer: (1) The Guanxian-Anxian fault, Yingxiu-Beichuan fault and Wenchuan-Maoxian fault of the Longmen Shan fault zone are well delineated by sharp upper crustal velocity changes; (2) The Pengguan massif has generally higher velocity than its surrounding areas, and may extend down to at least ~10 km from the surface; (3) A sharp lateral velocity variation beneath the Wenchuan-Maoxian fault may indicate that the Pengguan massif’s western boundary and/or the Wenchuan-Maoxian fault is vertical, and the hypocenter of the Wenchuan earthquake possibly located at the conjunction point of the NW dipping Yingxiu-Beichuan and Guanxian-Anxian faults, and vertical Wenchuan-Maoxian fault; (4) Vicinity along the Yingxiu-Beichuan fault is characterized by very low velocity and low seismicity at shallow depths, possibly due to high content of porosity and fractures; (5) Two blocks of low-velocity anomaly are respectively imaged in the hanging wall and foot wall of the Guanxian-Anxian fault with a ~7 km offset with ~5 km vertical component. 相似文献
19.
The characteristics and failure mechanism of the largest landslide triggered by the Wenchuan earthquake, May 12, 2008, China 总被引:9,自引:7,他引:2
Runqiu Huang Xiangjun Pei Xuanmei Fan Weifeng Zhang Shigui Li Biliang Li 《Landslides》2012,9(1):131-142
Strong earthquakes are among the prime triggering factors of landslides. The 2008 Wenchuan earthquake (M
w = 7.9) triggered tens of thousands of landslides. Among them, the Daguangbao landslide is the largest one, which covered
an area of 7.8 km2 with a maximum width of 2.2 km and an estimated volume of 7.5 × 108 m3. The landslide is located on the hanging wall of the seismogenic fault, the Yingxiu–Beichuan fault in Anxian town, Sichuan
Province. The sliding mass travelled about 4.5 km and blocked the Huangdongzi valley, forming a landslide dam nearly 600 m
high. Compared to other coseismic landslides in the study area, the Daguangbao landslide attained phenomenal kinetic energy,
intense cracking, and deformation, exposing a 1-km long head scarp in the rear of the landslide. Based on the field investigation,
we conclude that the occurrence of the landslide is controlled mainly by the seismic, terrain, and geological factors. The
special location of the landslide and the possible topographic amplification of ground motions due to the terrain features
governed the landslide failure. The effects of earthquakes on the stability of slopes were considered in two aspects: First,
the ground shaking may reduce the frictional strength of the substrate by shattering of rock mass. Second, the seismic acceleration
may result in short-lived and episodic changes of the normal (tensile) and shear stresses in the hillshopes during earthquakes.
According to the failure mechanism, the dynamic process of the landslide might contain four stages: (a) the cracking of rock
mass in the rear of the slope mainly due to the tensile stress generated by the ground shaking; (b) the shattering of the
substrate due to the ground shaking, which reduced the frictional strength of the substrate; (c) the shearing failure of the
toe of the landslide due to the large shear stress caused by the landslide gravity; and (d) the deposition stage. 相似文献
20.
Landslides and collapses occurred during the May 12th earthquake in Wenchuan County. Most of these landslides and collapses
were caused by shear bands. Shear band triggers instability on mountain slopes, resulting in debris flow, landslides, or collapse.
According to experimental results, there was only one shear band forming in the soil layer prior to the initiation of debris
flow under shear load, although several fine shear bands appeared. The development of shear bands in saturated soils is numerically
investigated in this paper using the in situ soil from the Weijia Gully, Beichuan County. The evolution of shear banding from
several finite amplitude disturbances (FADs) in pore pressure has been studied. The numerical analysis revealed that the FADs
evolved into a fully developed shear band. It is shown that the shear banding process consists of two stages: inhomogeneous
shearing and true shear banding. 相似文献