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1.
MonaLisa Azam A. Khwaja M. Qasim Jan Robert S. Yeats Ahmad Hussain Shahid A. Khan 《Journal of Seismology》2009,13(3):339-361
This paper deals with the data obtained from local networks in northern Pakistan for 251 earthquakes of magnitude ≥4.0 for
October 8, 2005 to December 31, 2006 period. The study presents focal mechanism solutions (FMS) of 12 pre- (1904–2005) and
17 post- (October 8, 2005–December, 2005) Muzaffarabad Earthquake, their detailed tectonic interpretation, and correlation
with surface evidence of co-seismic rupture with published synthetic aperture radar data. Distribution of landslides obtained
from National Engineering Services of Pakistan and the earthquake damages are also discussed. Aftershock distribution, which
is more prominent in the crystalline zone (northwest of Muzaffarabad), defines a 50-km-wide NW–SE trending zone that extends
for 200 km from the main mantle thrust to the center of the Hazara–Kashmir Syntaxis. The FMS of the main shock and 16 aftershocks
having magnitude ≥4.0 indicate thrusting to be the dominant mechanism with rupture planes having NW–SE trend and NE dip. In
addition, 12 FMS of pre-Muzaffarabad Earthquake (1904–2004) from the same area have been determined and results are compared.
This leads to the conclusion that the wedge-shaped NW–SE trending blind zone, referred to by earlier workers as the Indus
Kohistan Seismic Zone (IKSZ), has been activated during the Muzaffarabad earthquake. The right-lateral component in all FMS,
supported by the surface evidences, suggests the involvement of Balakot–Bagh Fault (BBF). We propose that the IKSZ is the
source of the October 8, 2005 Muzaffarabad earthquake that reactivated the BBF. Furthermore, the IKSZ does not end at the
nose of the syntaxis but extends further southeast of it. Tectonic complexity seems to be due to a variety of factors. Also,
thrust and reverse solutions near the northern collisional boundary (main mantle thrust) have mostly NE/SW-directed P-axis
orientations. From the detailed FMS analysis, three conclusions have been drawn: (1) Shallow events (depth ≤10 km) with prominent
strike slip solutions (earlier earthquakes) are associated with the surface strike slip faults (e.g., Muzaffarabad Fault)
and/or the Besham domal structure; (2) moderate depth events (depth 10–25 km) with thrust/reverse solutions but having minor
right-lateral strike slip component (all Muzaffarabad earthquakes and two earlier) are associated with the IKSZ; (3) deeper
earthquakes (depth below IKSZ) with pure thrust/reverse solutions may be related to the under-thrusting of the Indian plate
beneath the IKSZ, which represents a major thrust zone. Imbricate thrusting and breaking and thickening of the crust are considered
to be caused by steep bending of the under-thrusting plate at the collisional boundary.
An erratum to this article can be found at 相似文献
2.
We propose here that the 8 October 2005 North Pakistan earthquake occurred beneath the wedge-top of Balakot Formation in the
Hazara-Kashmir syntaxial area. Slip occurred along the Muzaffarabad thrust, a southeast extended part of the Indus-Kohistan
seismic zone. Tectonic loading of the high-density wedge/thrust sheet between the wedge-top and the descending Indian lithosphere
coupled with continued flexural tectonics provoked this earthquake. The obliquely converging Indian plate along with block
rotations led to development of a pinned zone around Northwestern Syntaxis of the Himalayas. Strain adjustment related to
the rotational deformation processes resulted in the buckling of the more competent rock-units sandwiched between the less
competent rock-units around the Hazara-Kashmir syntaxis. The western limb of the buckled unit gave rise to the development
of thrusts and associated oblique slip in the inner arc of the competent rock-unit. The observations demonstrate reactivated
tectonic movement along the growing fracture-tip of the buried Riasi thrust. 相似文献
3.
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
4.
Geologic evidence for late Quaternary repetitive surface faulting on the Isurugi fault along the northwestern margin of the Tonami Plain,north‐central Japan 
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下载免费PDF全文 Our detailed field investigation, paleoseismic trenching, and airborne light detection and ranging (LiDAR)‐derived topographic data provides the first direct evidence for late Quaternary repetitive surface faulting on the northeast‐striking Isurugi fault along the northwestern margin of the Tonami Plain in the Hokuriku region of north‐central Japan. This fault has been interpreted previously by different researchers as both inactive and active, owing to a lack of geologic evidence and a failure to identify fault‐related geomorphic features. Our mapping of LiDAR topography revealed a series of northeast‐trending warped fluvial terraces, about 1.5 km long and 170 m wide, with an age of ≤ 29 ka. We interpreted these geomorphologic features to represent an active pop‐up structure bounded to the southeast by the northwest‐dipping main thrust of the Isurugi fault and to the northwest by a southeast‐dipping backthrust that splays off the main thrust in the shallow subsurface. Paleoseismic trenching across the northwestern part of an elongate terrace exposed a series of southeast‐dipping backthrusts and associated northwest‐verging monoclines. The deformation and depositional age of the strata provide evidence for repetitive surface rupturing on the backthrusts since the latest Pleistocene; the latest of these events occurred in the Holocene between about 4.0 and 0.9 ka. Despite the poor preservation of the surface expression of the Isurugi fault, repetitive scarp‐forming faulting in the late Quaternary and the proximity of the Oyabe River and its tributaries to the fault trace suggest that there may be an extension of the Isurugi fault to the northeast and southwest beneath the Tonami Plain that makes the fault long enough to generate a large earthquake (Mw ≥ 6.8) accompanied by surface rupture. 相似文献
5.
利用2010~2016年阳江地区小震资料,对围绕广东阳江6.4级地震发震构造的NEE走向平冈断层的西南段及NW走向的程村断层展布的密集地震,经双差定位方法重新进行震源位置的修定,获得了1411个精定位震源资料。依据成丛地震发生在断层附近的原则,采用模拟退火算法及高斯-牛顿算法相结合的方式,较精确地获得了2个断层面的详细参数：即平冈断层西南段走向258°、倾角85°、倾向NW,与6.4级地震的震源机制解结果十分一致,断层长度约15km并穿过了其西南端海域抵达了对岸;程村断层走向331°、倾角88°、倾向NE,长度约28km,较已有结果更长、走向也朝NE向偏转了约15°。2条陡直断层近乎垂直相交于近海,在构造应力作用下均以走滑错动为主。 相似文献
6.
Focal mechanism and dynamic rupture process of the Wenchaun M
s8.0 earthquake in Sichuan province on 12 May 2008 were obtained by inverting long period seismic data from the Global Seismic
Network (GSN), and characteristics of the co-seismic displacement field near the fault were quantitatively analyzed based
on the inverted results to investigate the mechanism causing disaster. A finite fault model with given focal mechanism and
vertical components of the long period P-waves from 21 stations with evenly azimuthal coverage were adopted in the inversion.
From the inverted results as well as aftershock distribution, the causative fault of the great Wenchuan earthquake was confirmed
to be a fault of strike 225°/dip 39°/rake 120°, indicating that the earthquake was mainly a thrust event with right-lateral
strike-slip component. The released scalar seismic moment was estimated to be about 9.4×1020-2.0×1021 Nm, yielding moment magnitude of M
w7.9–8.1. The great Wenchuan earthquake occurred on a fault more than 300 km long, and had a complicated rupture process of
about 90 s duration time. The slip distribution was highly inhomogeneous with the average slip of about 2.4 m. Four slip-patches
broke the ground surface. Two of them were underneath the regions of Wenchuan-Yingxiu and Beichuan, respectively, with the
first being around the hypocenter (rupture initiation point), where the largest slip was about 7.3 m, and the second being
underneath Beichuan and extending to Pingwu, where the largest slip was about 5.6 m. The other two slip-patches had smaller
sizes, one having the maximum slip of 1.8 m and lying underneath the north of Kangding, and the other having the maximum slip
of 0.7 m and lying underneath the northeast of Qingchuan. Average and maximum stress drops over the whole fault plane were
estimated to be 18 MPa and 53 MPa, respectively. In addition, the co-seismic displacement field near the fault was analyzed.
The results indicate that the features of the co-seismic displacement field were coincident with those of the intensity distribution
in the meizoseismal area, implying that the large-scale, large-amplitude and surface-broken thrust dislocation should be responsible
for the serious disaster in the near fault area.
Supported by the National Basic Research Program of China (Grant No. 2004CB418404-4) and the National Natural Science Foundation
of China (Grant Nos. 40574025 and 40874026) 相似文献
7.
2008年2—4月,位于汶川大震初始破裂点的紫坪铺水库附近发生了一系列的小震活动,它们与汶川地震和紫坪铺水库小震的关系值得研究。本文采用CAP方法,反演了紫坪铺水库7个专用数字地震台站的数据,得到震级大于ML 1.0的28个震源机制解。结果表明:有19个地震事件集中在紫坪铺水库东南方向的都江堰附近,最大地震为逆冲型,发震机制为逆冲型带走滑分量,少量带正断层分量;从深度剖面看,地震震源深度主要集中分布在地下13km附近区域,都江堰震群丛集在前山断裂带上,其它地震散布在中央断裂带上;发震最大主压应力方向随时间的变化具有从最大主压应力方向变化比较大到趋向一致的演化过程。这些现象说明龙门山断裂带在都江堰附近存在1个凸凹体,形成应力集中点,引发都江堰震群活动,由此迫使龙门山断裂带前山断裂发生逆冲性活动,从而加剧了龙门山断裂带中央断裂的活动,在一定程度上加速了汶川地震的发生。 相似文献
8.
9.
明龙山-上窑断裂是一条逆走滑性质的第四纪活动断裂,长约68km,走向300°-315°。本文在卫星影像解译的基础上,通过野外调查,确定了该断裂的几何展布和分段特征,初步将断裂分为明龙山、上窑、凤阳山3条次级断裂段。通过对断裂经过处的采石场进行详细追索,我们对典型断层剖面进行了描述并采集了断层泥ESR样品,得到的测年结果为（243±24）ka和（126±15）ka,由于淮南地区是典型的中等强度地震活动区,断层晚第四纪以来活动强度较弱,这些测年结果虽不能代表断层最后一次微弱活动的时代,但可以确定断层最后一次强烈活动时代为中更新世晚期至晚更新世早期。结合前人对1831年凤台MS 6?级地震极震区位置、等震线形态研究及本文对极震区附近断裂展布和活动性的对比分析,我们认为明龙山-上窑断裂为本次地震发震构造的可能性最大。 相似文献
10.
THE RESEARCH OF THE SEISMOGENIC STRUCTURE OF THE LUSHAN EARTHQUAKE BASED ON THE SYNTHESIS OF THE DEEP SEISMIC DATA AND THE SURFACE TECTONIC DEFORMATION 下载免费PDF全文
下载免费PDF全文 WANG Lin ZHOU Qing-yun WANG Jun LI Wen-qiao ZHOU Lian-qing CHEN Han-lin SU Peng LIANG Peng 《地震地质》2016,38(2):458-476
The seismogenic structure of the Lushan earthquake has remained in suspensed until now. Several faults or tectonics, including basal slipping zone, unknown blind thrust fault and piedmont buried fault, etc, are all considered as the possible seismogenic structure. This paper tries to make some new insights into this unsolved problem. Firstly, based on the data collected from the dynamic seismic stations located on the southern segment of the Longmenshan fault deployed by the Institute of Earthquake Science from 2008 to 2009 and the result of the aftershock relocation and the location of the known faults on the surface, we analyze and interpret the deep structures. Secondly, based on the terrace deformation across the main earthquake zone obtained from the dirrerential GPS meaturement of topography along the Qingyijiang River, combining with the geological interpretation of the high resolution remote sensing image and the regional geological data, we analyze the surface tectonic deformation. Furthermore, we combined the data of the deep structure and the surface deformation above to construct tectonic deformation model and research the seismogenic structure of the Lushan earthquake. Preliminarily, we think that the deformation model of the Lushan earthquake is different from that of the northern thrust segment ruptured in the Wenchuan earthquake due to the dip angle of the fault plane. On the southern segment, the main deformation is the compression of the footwall due to the nearly vertical fault plane of the frontal fault, and the new active thrust faults formed in the footwall. While on the northern segment, the main deformation is the thrusting of the hanging wall due to the less steep fault plane of the central fault. An active anticline formed on the hanging wall of the new active thrust fault, and the terrace surface on this anticline have deformed evidently since the Quaterary, and the latest activity of this anticline caused the Lushan earthquake, so the newly formed active thrust fault is probably the seismogenic structure of the Lushan earthquake. Huge displacement or tectonic deformation has been accumulated on the fault segment curved towards southeast from the Daxi country to the Taiping town during a long time, and the release of the strain and the tectonic movement all concentrate on this fault segment. The Lushan earthquake is just one event during the whole process of tectonic evolution, and the newly formed active thrust faults in the footwall may still cause similar earthquake in the future. 相似文献
11.
四川龙泉山断裂带变形特征及其活动性初步研究 总被引：9，自引：3，他引：6
文中通过野外调查和地震反射剖面研究,获取了龙泉山断裂带的变形特征。龙泉山断裂带主逆冲断层位于龙泉山背斜的西翼,具有明显的分段性特征,北段与南段断层面倾向NW,断续分布;中段断层面倾向SE,形成典型的断层传播褶皱,并且断层已经沿背斜前翼膝折带的轴突破,形成贯通的突破断层。因此,中段构成了龙泉山断裂的主体。地貌对断裂活动性的响应表明龙泉山断裂早更新世—晚更新世有过一定的活动,晚更新世以来活动速率较低,且活动性具有从南向北逐渐减弱的趋势 相似文献
12.
13.
William Menke Hannah Abend Dalia Bach Kori Newman Vadim Levin 《Surveys in Geophysics》2006,27(6):603-613
The December 26, 2004 Sumatra–Andaman Island earthquake, which ruptured the Sunda Trench subduction zone, is one of the three largest earthquakes to occur since global monitoring began in the 1890s. Its seismic moment was M
0 = 1.00 × 1023–1.15 × 1023 Nm, corresponding to a moment-magnitude of M
w
= 9.3. The rupture propagated from south to north, with the southerly part of fault rupturing at a speed of 2.8 km/s. Rupture propagation appears to have slowed in the northern section, possibly to ∼2.1 km/s, although published estimates have considerable scatter. The average slip is ∼5 m along a shallowly dipping (8°), N31°W striking thrust fault. The majority of slip and moment release appears to have been concentrated in the southern part of the rupture zone, where slip locally exceeded 30 m. Stress loading from this earthquake caused the section of the plate boundary immediately to the south to rupture in a second, somewhat smaller earthquake. This second earthquake occurred on March 28, 2005 and had a moment-magnitude of M
w
= 8.5. 相似文献
14.
黑龙江省萝北地区是东北现代地震活动最为活跃的地区之一,中小地震密集成带分布,曾于1963年发生5.8级地震,但其发震构造一直不清楚。精定位后的震中分布图像和震源机制解研究结果表明,现代地震总体呈NEE方向密集分布于黑龙江小兴安岭山前太平沟一带,地震类型以右旋走滑为主。通过高分辨率的卫星影像解译结果发现太平沟一带发育一条长约25km,走向约N70°E的线性异常带。野外地表调查发现该线性异常表现为断续分布的断裂陡坎、冲沟位错和滑坡。陡坎走向约N65°E-N75°E,倾向SE,高约1.0-2.5m;滑坡发育有典型的弧形圈椅构造,规模大小不等,多与断裂陡坎伴生。综合现代地震活动图像、卫星影像解译、野外地质调查结果,特别是结合2013年11月和2014年2月该地区的2次小震活动及现代地震活动的空间图像分布特征,研究认为太平沟断裂属于依兰-伊通断裂带的分支断裂,晚第四纪期间曾经强烈活动,具备中强地震的发震能力,可能是萝北1963年5.8级地震的发震构造。 相似文献
15.
Lijiang-Daju fault, the seismogenic fault of the 1996 Lijiang M=7.0 earthquake, can be divided into Lijiang-Yuhu segment in the south and Yuhu-Daju segment in the north. The two segments show clear difference in geological tectonics, but have the similar dynamic features. Both normal dip-slip and sinistral strike-slip coexist on the fault plane. This kind of movement started at the beginning of the Quaternary (2.4～2.5 Ma B.P.). As to the tectonic types, the detachment fault with low angle was developed in the Early Pleistocene and the normal fault with high angle only after the Mid-Pleistocene (0.8 Ma B.P.). Based on the horizontal displacements of gullies and the vertical variance of planation surfaces cross the Lijiang-Daju fault at east piedmont of Yulong-Haba range, the average horizontal and vertical slip rates are calculated. They are 0.84 mm/a and 0.70 mm/a since the Quaternary and 1.56 mm/a and 1.69 mm/a since the Mid-Pleistocene. The movements of the nearly N-S-trending Lijiang-Daju fault are controlled not only by the regional stress field, but also by the variant movement between the Yulong-Haba range and Lijiang basin. The two kinds of dynamic processes form the characteristics of seismotectonic environment of occurring the 1996 Lijiang earthquake. 相似文献
16.
贵州沿河MS4.9地震发生在历史地震强度较低的上扬子地块凤冈SN向隔槽式褶皱变形区。通过地震地质背景分析、震害调查、震源机制解、断层调查和库区水位变化情况等,得到主要认识如下:由于震源深度浅、灾区老旧自建房抗震性能差,导致本次地震直接经济损失严重;本次地震主震的机制解为节面Ⅰ:走向61°/倾角35°/滑动角135°,节面Ⅱ:走向190°/倾角66°/滑动角63°,表现为走向NE、逆冲兼平移型运动方式;结合等震线走向及震中主要断层性质,判断NE向沿河断层为本次地震主震的发震构造,并进一步推测此次地震为水库诱发断层活化引起的地震。 相似文献
17.
Based on the latest displacement of Huoshan piedmont fault, Mianshan west-side fault and Taigu fault obtained from the beginning of 1990‘s up to the present, the characteristics of distribution and displacement of surface rupture zone of the 1303 Hongtong M = 8 earthquake, Shanxi Province are synthesized and discussed in the paper. If Taigu fault, Mianshan west-side fault and Huoshan piedmont fault were contemporarily active during the 1303 Hongtong M = 8 earthquake, the surface rupture zone would be 160 km long and could be divided into 3 segments, that is, the 50-km-long Huoshan piedmont fault segment, 35-km-long Mianshan west-side fault segment and 70-km-long Taigu fault segment, respectively. Among them, there exist 4 km and 8 km step regions. The surface rupture zone exhibits right-lateral features. The displacements of northern and central segments are respectively 6～7 m and the southern segment has the maximum displacement of 10 m. The single basin-boundary fault of Shanxi fault-depression system usually corresponds to M ≈ 7 earthquake, while this great earthquake (M = 8) broke through the obstacle between two basins. It shows that the surface rupture scale of great earthquake is changeable. 相似文献
18.
19.
扶余肇东断裂带是松辽盆地中一条重要的隐伏发震断裂带,2006年和2014年在此断裂带上发生了多次近6级地震,地震活动主要集中在断裂的东北段和查干花段。在2012—2014年的松原市活断层探测工作中,探明扶余肇东断裂带东北段经过松原市区,该段呈近EW向,具有明显的分段性和独立性,将其命名为扶余北断裂。通过三维物探资料和浅层人工探测,确定了扶余北断裂的空间展布和剖面特征,并利用联排钻孔探测和光释光测年技术,确定该断裂存在晚更新世以来的活动;利用石油物探资料获得的基岩面破裂规模,对扶余北断裂的地震潜势进行了估计,并进行了概率性地震危险性研究。 相似文献
20.
The magnitude (M
w) 7.9 Wenchuan earthquake occurred on 12 May 2008 in the Longmen Shan region of China, the transition zone between the Tibetan
Plateau and the Sichuan Basin, resulting in widespread damage throughout central and western China. The steep, high-relief
eastern margin of the Tibetan Plateau has undergone rapid Cenozoic uplift and denudation accompanied by folding and thrusting,
yet no large thrust earthquakes are known prior to the 2008 M
w 7.9 Wenchuan earthquake. Field and excavation investigations reveal that a great historical earthquake occurred in the Sichuan
region that ruptured a >200-km-long thrust fault within the Longmen Shan Thrust Belt, China, which also triggered the 2008
M
w 7.9 Wenchuan earthquake. The average co-seismic slip amount produced by this historical earthquake is estimated to be 2–3 m,
comparable with that caused by the 2008 Wenchuan earthquake. Paleoseismic and archaeological evidence and radiocarbon dating
results show that the penultimate great earthquake occurred in the Sichuan region during the late Tang-Song Dynasty, between
AD 800 and 1000, suggesting a recurrence interval of ~1,000–1,200 years for Wenchuan-magnitude (M = ~8) earthquakes in the late Holocene within the Longmen Shan Thrust Belt. This finding is in contrast with previous estimates
of 2,000–10,000 years for the recurrence interval of large earthquakes within the Longmen Shan Thrust Belt, as obtained from
long-term slip rates based on the Global Positioning System and geological data, thereby necessitating substantial modifications
to existing seismic-hazard models for the densely populated region at the eastern marginal zone of the Tibetan Plateau. 相似文献