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1.
The Garzê–Yushu strike-slip fault in central Tibet is the locus of strong earthquakes(M 7). The deformation and geometry of the co-seismic surface ruptures are reflected in the surface morphology of the fault and depend on the structure of the upper crust as well as the pre-existing tectonics. Therefore, the most recent co-seismic surface ruptures along the Garzê–Yushu fault zone(Dangjiang segment) reveal the surface deformation of the central Tibetan Plateau. Remote sensing images and field investigations suggest a 85 km long surface rupture zone(striking NW-NWW), less than 50 m wide, defined by discontinuous fault scarps, right-stepping en echelon tensional cracks and left-stepping mole tracks that point to a left-lateral strike-slip fault. The gullies that cross fault scarps record systematic left-lateral offsets of 1.8 m to 5.0 m owing to the most recent earthquake, with moment magnitude of about M 7.5, in the Dangjiang segment. Geological and geomorphological features suggest that the spatial distribution of the 1738 co-seismic surface rupture zone was controlled by the pre-existing active Garzê–Yushu fault zone(Dangjiang segment). We confirm that the Garzê–Yushu fault zone, a boundary between the Bayan Har Block to the north and the Qiangtang Block to the south, accommodates the eastward extrusion of the Tibetan Plateau and generates strong earthquakes that release the strain energy owing to the relative motion between the Bayan Har and Qiangtang Blocks. 相似文献
2.
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
3.
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
4.
DONG Shuwen 《《地质学报》英文版》2009,83(4)
Abstract: On May 12th, 2008, the Mw7.9 Wenchuan earthquake ruptured the Beichuan, Pengguan and Xiaoyudong faults simultaneously along the middle segment of the Longmenshan thrust belt at the eastern margin of the Tibetan plateau. Field investigations constrain the surface rupture pattern, length and offsets related to the Wenchuan earthquake. The Beichuan fault has a NE-trending right-lateral reverse rupture with a total length of 240 km. Reassessment yields a maximum vertical offset of 6.5±0.5 m and a maximum right-lateral offset of 4.9±0.5 m for its northern segment, which are the largest offsets found; the maximum vertical offset is 6.2±0.5 m for its southern segment. The Pengguan fault has a NE-trending pure reverse rupture about 72 km long with a maximum vertical offset of about 3.5 m. The Xiaoyudong fault has a NW-striking left-lateral reverse rupture about 7 km long between the Beichuan and Pengguan faults, with a maximum vertical offset of 3.4 m and left-lateral offset of 3.5 m. This pattern of multiple co-seismic surface ruptures is among the most complicated of recent great earthquakes and presents a much larger danger than if they ruptured individually. The rupture length is the longest for reverse faulting events ever reported. 相似文献
5.
MA Yinsheng LONG Changxing TAN Chengxuan WANG Tao GONG Mingquan LIAO Chunting WU Manlu SHI Wei DU Jianjun PAN Feng 《《地质学报》英文版》2009,83(4):713-723
Abstract: There are two co-seismic faults which developed when the Wenchuan earthquake happened. One occurred along the active fault zone in the central Longmen Mts. and the other in the front of Longmen Mts. The length of which is more than 270 km and about 80 km respectively. The co-seismic fault shows a reverse flexure belt with strike of N45°–60°E in the ground, which caused uplift at its northwest side and subsidence at the southeast. The fault face dips to the northwest with a dip angle ranging from 50° to 60°. The vertical offset of the co-seismic fault ranges 2.5–3.0 m along the Yingxiu-Beichuan co-seismic fault, and 1.5–1.1 m along the Doujiangyan-Hanwang fault. Movement of the co-seismic fault presents obvious segmented features along the active fault zone in central Longmen Mts. For instance, in the section from Yingxiu to Leigu town, thrust without evident slip occurred; while from Beichuan to Qingchuan, thrust and dextral strike-slip take place. Main movement along the front Longmen Mts. shows thrust without slip and segmented features. The area of earthquake intensity more than IX degree and the distribution of secondary geological hazards occurred along the hanging wall of co-seismic faults, and were consistent with the area of aftershock, and its width is less than 40km from co-seismic faults in the hanging wall. The secondary geological hazards, collapses, landslides, debris flows et al., concentrated in the hanging wall of co-seismic fault within 0–20 km from co-seismic fault. 相似文献
6.
Surface Rupture of the 1515 Yongsheng Earthquake in Northwest Yunnan,and Its Seismogeological Implications 总被引：2，自引：0，他引：2
The 1515 M7? Yongsheng earthquake is the strongest earthquake historically in northwest Yunnan. However, its time, magnitude and the seismogenic fault have long been a topic of dispute. In order to accurately define those problems, a 1:50000 active tectonic mapping was carried out along the northern segment of the Chenghai–Binchuan fault zone. The result shows that there is an at least 25 km–long surface rupture and a series of seismic landslides distributed along the Jinguan fault and the Chenghai fault. Radiocarbon dating of the ~(14) C samples indicates that the surface rupture should be a part of the deformation zone caused by the Yongsheng earthquake in the year 1515. The distribution characteristics of this surface rupture indicate that the macroscopic epicenter of the 1515 Yongsheng earthquake may be located near Hongshiya, and the seismogenic fault of this earthquake is the Jinguan–Chenghai fault, the northern part of the Chenghai–Binchuan fault zone. Striations on the surface rupture show that the latest motion of the fault is normal faulting. The maximum co–seismic vertical displacement can be 3.8 m, according to the empirical formula for the fault displacement and moment magnitude relationship, the moment magnitude of the Yongsheng earthquake was Mw 7.3–7.4. Furthermore, combining published age data with the ~(14) C data in this paper reveals that at least four large earthquakes of similar size to the 1515 Yongsheng earthquake, have taken place across the northern segment of the Chenghai–Binchuan fault zone since 17190±50 yr. BP. The in–situ recurrence interval of Mw 7.3–7.4 characteristic earthquakes in Yongsheng along this fault zone is possibly on the order of 6 ka. 相似文献
7.
Parameters of Coseismic Reverse‐ and Oblique‐Slip Surface Ruptures of the 2008 Wenchuan Earthquake,Eastern Tibetan Plateau 总被引：4，自引：0，他引：4
XU Xiwei YU Guihu CHEN Guihu RAN Yongkang LI Chenxi CHEN Yuegau CHANG Chungpai 《《地质学报》英文版》2009,83(4):673-684
Abstract: On May 12th, 2008, the Mw7.9 Wenchuan earthquake ruptured the Beichuan, Pengguan and Xiaoyudong faults simultaneously along the middle segment of the Longmenshan thrust belt at the eastern margin of the Tibetan plateau. Field investigations constrain the surface rupture pattern, length and offsets related to the Wenchuan earthquake. The Beichuan fault has a NE-trending right-lateral reverse rupture with a total length of 240 km. Reassessment yields a maximum vertical offset of 6.5±0.5 m and a maximum right-lateral offset of 4.9±0.5 m for its northern segment, which are the largest offsets found; the maximum vertical offset is 6.2±0.5 m for its southern segment. The Pengguan fault has a NE-trending pure reverse rupture about 72 km long with a maximum vertical offset of about 3.5 m. The Xiaoyudong fault has a NW-striking left-lateral reverse rupture about 7 km long between the Beichuan and Pengguan faults, with a maximum vertical offset of 3.4 m and left-lateral offset of 3.5 m. This pattern of multiple co-seismic surface ruptures is among the most complicated of recent great earthquakes and presents a much larger danger than if they ruptured individually. The rupture length is the longest for reverse faulting events ever reported. 相似文献
8.
Revisiting Late Quaternary Slip-rate along the Maqu Segment of the Eastern Kunlun Fault,Northeast Tibet 总被引：1，自引：0，他引：1
The Late Quaternary slip rate along the Maqu segment of the eastern Kunlun Fault was estimated using a combination of high-resolution remote sensing imagery interpretation, field observations and differential Global Positioning System(GPS) measurements of offset river terraces, and 14 C dating of snail shells collected from offset risers. The results show that the left-slip rate along the segment is 3–5 mm/a, and that the vertical slip rate is 0.3–0.5 mm/a. Both the horizontal and vertical slips on the segment remain consistent over a distance of ~100 km. It means that no slip gradient as previously suggested occurred along the Maqu segment, and which thus might behave as an independent seismogenic fault. Judging from multiple relationships among young terrace offsets, we infer that co-seismic surface rupture produced by a characteristic earthquake with a magnitude of Ms7.0–7.5 on the Maqu fault could generate a horizontal slip of 4.5–5 m and a vertical slip of 0.45–0.5 m, with a corresponding ratio(Dh/Dv) of about 9. Two surface rupture events must have occurred over the past 3300 years, the latest one possibly between 1485 cal BP and 1730 cal BP. 相似文献
9.
SUN Dongsheng WANG Lianjie WANG Hongcai MA Yinsheng ZHOU Chunjing and CUI Junwen 《《地质学报》英文版》2013,87(4):1120-1128
The variation of in situ stress before and after earthquakes is an issue studied by geologists. In this paper, on the basis of the fault slip dislocation model of Wenchuan Ms8.0 earthquake, the changes of co-seismic displacement and the distribution functions of stress tensor around the Longmen Shan fault zone are calculated. The results show that the co-seismic maximum surface displacement is 4.9 m in the horizontal direction and 6.5 m in the vertical direction, which is almost consistent with the on-site survey and GPS observations. The co-seismic maximum horizontal stress in the hanging wall and footwall decreased sharply as the distance from the Longmen Shan fault zone increased. However, the vertical stress and minimum horizontal stress increased in the footwall and in some areas of the hanging wall. The study of the co-seismic displacement and stress was mainly focused on the long and narrow region along the Longmen Shan fault zone, which coincides with the distribution of the earthquake aftershocks. Therefore, the co-seismic stress only affects the aftershocks, and does not affect distant faults and seismic activities. The results are almost consistent with in situ stress measurements at the two sites before and after Wenchuan Ms8.0 earthquake. Along the fault plane, the co-seismic shear stress in the dip direction is larger than that in the strike direction, which indicates that the faulting mechanism of the Longmen Shan fault zone is a dominant thrust with minor strike-slipping. The results can be used as a reference value for future studies of earthquake mechanisms. 相似文献
10.
ZHANG Jin YUN Long ZHANG Beihang QU Junfeng ZHAO Heng HUI Jie WANG Yannan ZHANG Yiping 《《地质学报》英文版》2020,94(4):988-1006
How the Altyn Tagh fault(ATF) extends eastwards is one of the key questions in the study of the growth of the Qinghai–Tibetan Plateau. Detailed fieldwork at the easternmost part of the ATF shows that the ATF extends eastward and bypasses the Kuantan Mountain; it does not stop at the Kuantan Mountain, but connects with the northern Heishan fault in the east. The ATF does not enter the Alxa Block but extends eastward along the southern Alxa Block to the Jintanan Mountain. The Heishan fault is not a thrust fault but a sinistral strike-slip fault with a component of thrusting and is a part of the ATF. Further to the east, the Heishan fault may connect with the Jintananshan fault. A typical strike-slip duplex develops in the easternmost part of the ATF. The cut and deformed Quaternary sediments and displaced present gullies along the easternmost ATF indicate that it is an active fault. The local highest Mountain(i.e., the Kuantan Mountain) in the region forms in a restraining bend of the ATF due to the thrusting and uplifting. The northward growth of the Qinghai–Tibetan Plateau and the active deformation in South Mongolia are realized by sinistral strike-slipping on a series of NE–SW-trending faults and thrusting in restraining bends along the strike-slip faults with the northeastward motion of blocks between these faults. 相似文献
11.
A nearly 100-km-long surface rupture zone, called Chelungpu surface rupture zone, occurred mostly along the pre-existing Chelungpu fault on the northwestern side of Taiwan, accompanying the 1999 Chi-Chi Ms 7.6 earthquake. The Chelungpu surface rupture zone can be divided into four segments based on the characteristics of co-seismic displacements, geometry of the surface ruptures and geological structures. These segments generally show a right-step en echelon form and strike NE–SW to N–S, and dip to the east with angles ranging from 50 to 85°. The co-seismic flexural-slip folding structures commonly occurred in or near the surface rupture zone from a few meters to a few hundreds of meters in width, which have an orientation in fold axes parallel or oblique to the surface rupture zone. The displacements measured in the southern three segments are approximately 1.0–3.0 m horizontally and 2.0–4.0 m vertically. The largest displacements were measured in the northern segment, 11.1 m horizontally and 7.5 m vertically, respectively. The amount of co-seismic horizontal shortening caused by flexural-slip folding and reverse faulting in the surface rupture zone is generally less than 3 m. It is evident that the co-seismic displacements of the surface rupture zone are a quantitative surface indicator of the faulting process in the earthquake source fault. The relations between the geometry and geomorphology of the surface rupture zone, dips of the co-seismic faulting planes and the striations on the main fault planes generated during the co-seismic displacement, show that the Chelungpu surface rupture zone is a reverse fault zone with a large left-lateral component. 相似文献
12.
四川汶川MS 8.0大地震地表破裂带的遥感影像解析 总被引：21，自引：1，他引：20
2008年5月12日发生于四川盆地西部龙门山断裂带的汶川MS 8.0级大地震造成巨大的人员伤亡和财产损失,并形成了空间上基本连续分布的地表破裂带（地震断层）。根据地表破裂带的解译标志及影像特征,我们充分利用震后中国科学院航空遥感飞机所获取的高分辨率航空遥感图像以及我国台湾福卫-2卫星遥感图像进行详细解译分析,并结合震后的多次野外科学考察与验证,初步查明了四川汶川MS 8.0级大地震所产生地表破裂带的空间分布特征。遥感解译分析表明汶川大地震产生的地表破裂带总计长约300 km,其几何学特征十分复杂,主要沿先存的NE走向活动断裂带呈不连续展布;变形特征以逆冲挤压为主兼具右旋走滑分量。按同震地表破裂带所在断裂带位置,可将其分为两条： 中央地表破裂带：沿映秀-北川断裂带分布,从西南开始呈北东向延伸至平武县水观乡石坎子北东一带,长约230 km,最大垂直位移量达6.0 m左右,最大右旋水平位移达5.8 m;山前地表破裂带：沿灌县-安县断裂带分布,由都江堰市向峨乡一带开始呈北东向延伸至安县雎水镇一带,长约70 km,以逆冲挤压为主,最大垂直位移量可达2.5 m。此外,遥感图像分析还表明上述地表破裂带与地质灾害分布在空间上具有十分密切的相关性,因此,挤压逆冲-走滑型地震断层的致灾效应研究是未来应该加以重视的研究课题。 相似文献
13.
14.
Complex geometry and segmentation of the surface rupture associated with the 14 November 2001 great Kunlun earthquake, northern Tibet, China 总被引：8，自引：0，他引：8
The 14 November 2001 Kunlun, China, earthquake with a moment magnitude (Mw) 7.8 occurred along the Kusai Lake–Kunlun Pass fault of the Kunlun fault system. We document the spatial distribution and geometry of surface rupture zone produced by this earthquake, based on high-resolution satellite (Landsat ETM, ASTER, SPOT and IKONOS) images combined with field measurements. Our results show that the surface rupture zone can be divided into five segments according to the geometry of surface rupture, including the Sun Lake, Buka Daban–Hongshui River, Kusai Lake, Hubei Peak and Kunlun Pass segments from west to east. These segments, each 55 to 130 km long, are separated by step-overs. The Sun Lake segment extends about 65 km with a strike of N45° 75°W (between 90°05′E 90°50′E) along the previously unrecognized West Sun Lake fault. A gap of about 30 km long exists between the Sun Lake and Buka Daban Peak where no obvious surface ruptures can be observed either from the satellite images or field observations. The Buka Daban–Hongshui River, Kusai Lake, Hubei Peak and Kunlun Pass segments run about 365 km striking N75° 85°W along the southern slope of the Kunlun Mountains (between 91°07′E 94°58′E). This segmentation of the surface rupture is well correlated with the pattern of slip distribution measured in the field. Detailed mapping suggest that these five first-order segments can be further separated into over 20 second-order segments with a length of 10–30 km, linked by smaller scale step-overs or bends.Our result also shows that the total coseismic surface rupture length produced by the 2001 Kunlun earthquake is about 430 km (excluding the 30-km-long gap), which is the longest coseismic surface rupture for an intracontinental earthquake ever recorded.Finally, we suggest a multiple bilateral rupture propagation model that shows the rupture process of the 2001 Mw 7.8 earthquake is complex. It consists of westward and eastward rupture propagations and interaction of these bilateral rupture processes. 相似文献
15.
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
16.
汶川8.0地震地表破裂平通镇段的变形特征 总被引：16，自引：11，他引：5
2008年5月12日14时28分04秒,四川省汶川县发生MS8.0大地震。发震断裂为龙门山断裂带,地震地表破裂带分布在北川-映秀断裂上的映秀-石坎子段和江油-灌县断裂上的磁峰-睢水段。平武县平通镇地表破裂现象典型,在T1和T2阶地上形成了地震断坎和裂缝。应用高精度GPSRTK技术对平通镇地震断坎及两侧作详细的地形测量,并测量了线性显著的路面中线和鱼塘西边壁。在室内生成高分辨率DEM与大比例尺地形剖面图,量取同震垂直与水平位移,并估算压缩缩短量和断层产状。结果显示汶川8.0级地震在平通镇形成的同震垂直位移为3.0±0.1m,右旋水平位移为4.0±0.2m,压缩缩短量为2.5m,断层产状为NE40°/NW∠50°。平通镇的同震右旋位移与本次地震的最大右旋位移相近,而逆冲垂直位移有所降低。 相似文献
17.
2010年4月14日青海省玉树县发生Ms7.1级地震。利用地震前后2期ALOS雷达数据进行了地表同震形变场InSAR解译研究,获取了高质量的干涉图像,并解算出定量变形场。进而根据干涉计算的变形方向、变形范围、变形量和变形梯度,参考该区的构造背景和走滑断裂的力学机理对本次地震构造活动进行了分析并得出如下结论：1）玉树地震引发了地表NWW走向、由5段构成的“S”形走滑断裂,总体为左阶排列,走滑量从10.2 cm到133.2 cm不等,走滑极值可达195 cm,其中在结古镇和隆宝镇附近的两段出现较明显的地表破裂;2）断裂两侧的雷达视线向运动方向和运动量的差异预示发震断裂以左旋走滑运动为主,SW盘为主动盘;3）宏观震中可以定位于玉树县城西北约16 km的地表陡变带附近;4）发震断裂地表行迹、变形量和地表破裂幅度预示余震将主要沿发震断裂向NW迁移;5）根据青藏高原东部地块的分区,本次地震属于羌塘地块活动的结果,与巴颜喀拉地块活动引发的汶川地震不存在直接的关联。 相似文献
18.
四川汶川5.12大地震同震滑动断层泥的发现及意义 总被引：4，自引：0，他引：4
2008年汶川8.0级地震沿龙门山断裂带内的映秀—北川断裂和灌县—安县断裂产生了近300 km的同震地表破裂带。震后地质科学考察发现地表变形以逆冲为主,并伴有右旋走滑。地震地表破裂带大多沿古生代碳质泥岩、页岩和三叠系煤系地层内的滑动面出露地表,这些软弱地层为地震破裂带冲到地表提供了超低摩擦滑动带。我们发现在同震垂直和水平位错达6m左右的地表破裂带,地震的同震滑动发生在厚度约0.5~2cm 的狭窄滑动带内,以发育新鲜的灰色断层泥为特征,这些断层泥是地震断层快速滑动过程中岩石—流体相互作用的结果。 相似文献
19.
汶川大地震（MS 8.0）同震变形作用及其与地质灾害的关系 总被引：12，自引：2，他引：10
2008年5月12日发生于四川盆地西部龙门山断裂带的汶川大地震（MS 8.0）波及半个亚洲,震撼整个中国。本文通过地震后的实地调查,对发育在龙门山断裂带上的同震地表破裂带的分布、产状、继承性复活与变形特征,以及同震变形与地震地质灾害的关系等进行了初步总结,分析表明这次汶川大地震(MS 8.0)沿北川-映秀逆冲断裂和安县-灌县逆冲断裂同时发生地表破裂,前者产生以高角度逆冲兼右旋走滑为特征的地表破裂带长约275 km,后者产生以缓倾角逆冲作用为特征的地表破裂带长约80 km。汶川大地震的同震地表破裂带分布具有分段性特征,并与地表破坏程度的分带性有着一定的内在联系,详细研究表明,同震地表破裂带的产状直接影响地表破坏程度和地震地质灾害的强度,汶川大地震（MS 8.0）沿呈高角度陡倾的北川-映秀逆冲断裂发育的同震地表变形所产生的地表破坏程度和地震地质灾害的强度比沿缓倾角的安县-灌县逆冲断裂要强。从各种类型的地震断裂来看,具有垂直运动的逆冲型地震断裂所造成的地表破坏程度和地质灾害强度比具水平运动的走滑型地震断裂要强。因此,汶川大地震发生的破裂过程和同震地表变形与地震地质灾害的关系值得深入研究。 相似文献