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1.
This paper presents a study of the damage due to the Mw 7.6–7.7 intraplate Kutch earthquake of 26 January 2001. It was a powerful earthquake with a high stress drop of about 20 MPa. Aftershocks (up to M 4) have continued for 2.5 years. The distribution of early aftershocks indicates a rupture plane of 20–25 km radius at depths of 10–45 km along an E–W-trending and south-dipping hidden fault situated approximately 25 km north of the Kutch Mainland Fault. The moment tensor solution determined from regional broadband data indicates reverse motion along a south-dipping (by 47°) fault. The earthquake is the largest event in India in the last 50 years and the most destructive in the recorded history in terms of socioeconomic losses with 13,819 deaths (including 14 in Pakistan), collapse/severe damage of over a million houses and US$10 billion economic loss. Surface faulting was not observed. However, intense land deformations have been observed in a 40×20-km meizoseismal area. These include lateral spreading, ground uplifts (about a meter), ground slumping and deep cracks. Liquefaction with ejection of sand and copious water was widespread in the Banni grassland, Rann areas (salt plains), along rivers and also in the coastal areas up to 200 km distance from the epicenter in areas of intensity VII to X+. Stray incidences of liquefaction have occurred up to distances of at least 300 km. For the first time in India, multistory buildings have been destroyed/damaged by an earthquake. The maximum acceleration is inferred to be 700 cm/s2 and intensities are 1–3 units higher in soil-covered areas than expected from the decay rate of acceleration for hard rock. 相似文献
2.
最近20年地震中场地液化现象的回顾与土体液化可能性的评价准则 总被引：1，自引：0，他引：1
回顾了1994年美国Northridge地震、1995年日本阪神地震、1999年土耳其Kocaeli地震、1999年台湾集集地震、2008年中国汶川地震、2010年智利Maule地震、2010~2011新西兰Darfield地震及余震、2011年东日本地震中大量的、不同类型的液化实例调查与研究,发现这些地震的液化具有以下特点:(1)罕见的特大地震(Mw9.0)使远离震中300~400 km的新近人工填土发生严重的大规模液化;(2)特大地震(Ms8.0、Mw8.8)使远离震中的低烈度Ⅴ~Ⅵ度地区发生严重液化;(3)海岸、河岸附近地区的新近沉积冲积、湖积土,填筑时间不到50年的含细粒、砂砾人工填土,容易发生严重液化;(4)天然的砂砾土层液化发生严重液化;(5)发生了深达20 m的土层液化现象;(6)松散土层液化后可以恢复到震前状态并再次发生液化;(7)高细粒(粒径≤75 m)含量≥50%或高黏粒(粒径≤5 m)含量≥25%的低-中塑性土严重液化,对介于类砂土与类黏土之间的过渡性态土,有时地表未见液化现象;(8)液化土层的深度较深或厚度较小时,容易出现地面裂缝而无喷砂现象;有较厚的上覆非液化土层时,场地液化不一定伴随地表破坏。液化实例证明,第四系晚更新世Q3地层可以发生严重液化;黏粒含量不是评价细粒土液化可能性的一个可靠指标;低液限、高含水率的细粒土易发生液化,采用塑性指数PI、含水率wc与液限LL之比作为细粒土液化可能性评价的指标是适宜的。综合Boulanger和Idriss、Bray和Sincio、Seed和Cetin等的液化实例调查与室内试验研究成果,建议细粒土液化可能性的评价准则如下:PI12且wc/LL0.85的土为易液化土,12PI≤20和/wc/LL≥0.80的土为可液化土;PI20或wc/LL0.80的土为不液化土。 相似文献
3.
The Yaojiachezhan (YJCZ) section and NGN1, Zk3389 and SK1-S wells, which are located in the southeastern part of the Songliao Basin, NE China, were used to analyse paleoseismic events recorded in the Upper Cretaceous first member of the Nenjiang Formation. Two representative seismic sequences are recognised in these lacustrine deposits. The seismic sequence observed in the YJCZ section, from the base to top, includes step micro-faulting, seismic fissures, liquefaction sandstone veins, brecelated structures, liquefied fold-deformed laminations and sand pillow structures. Whereas in NGN1 core, from the base to top, includes micro-faulting, seismic fissures, sand pillow structures, liquefied fold-deformed laminations and liquefaction sandstone veins. These two seismic sequences together reflect the processes resulting from a strong seismic event from initiation to culmination, then decline and recession. The occurrence of brecciated structures reflects the earthquake magnitude in the YJCZ section area probably reached M7.5, while liquefied fold-deformed laminations in the NGN1 core area reflects an earthquake magnitude of M7.0. Empirical relations between earthquake magnitude and the maximum distance of liquefaction deformation structure sites from the epicentres show that the longest distance between the earthquake source area for the YJCZ section and NGN1 well are <100?km, whereas the distance for the Zk3389 and SK1-S wells is >100?km. The trigger source area for this paleoseismic event is most likely the Yilan-Yitong Fault, meaning that the Yilan-Yitong Fault was active during the deposition of the first member of the Nenjiang Formation. 相似文献
4.
ZHANG Yueqiao DONG Shuwen HOU Chuntang SHI Jusong WU Zhonghai LI Hailong SUN Ping LIU Gang LI Jian 《《地质学报》英文版》2013,87(3):633-645
At 08:02 on April 20, 2013, a Ms7.0 earthquake occurred in Lushan, Ya'an, in the Longmenshan fault zone, Sichuan. The epicenter was located between Taiping Town and Shuangshi Town, Lushan County and the maximum earthquake intensity at the epicenter reached class IX. Field investigations in the epicenter area found that, although buildings were seriously damaged, no obvious surface rupture structure was produced, only some ground fissures and sand blows and water ejection phenomena being seen. An integrated analysis of high-resolution remote sensing image interpretation, mainshock and aftershock distribution, and focal mechanism solutions indicated that this earthquake was an independent rupturing event in the southwestern segment of the Longmenshan fault zone, belonging to the thrust-type earthquake. Ruptures occurred along the south-central segment of the Shuangshi-Dachuan fault and the principal rupture plane dipped SW at 33-43°. It is inferred that the Lushan earthquake might be related to the ramp activity of the basal detachment zone (13-19 km) of the Longmenshan fault zone. Historically, there occurred at least two Ms6-6.5 earthquakes along the Shuangshi-Dachuan fault zone; thus it is thought that the Lushan earthquake, different from the Wenchuan earthquake, was a characteristic one in the southwestern segment of the Longmenshan fault zone. In-situ stress measurements indicated the Lushan earthquake was the result of stress release of the southwestern segment of the Longmenshan fault zone after the Wenchuan earthquake. This paper analyzes the tectonic setting of the seismogenic structure of this earthquake. 相似文献
5.
R.T. Cox A.A. Hill D. Larsen T. Holzer S.L Forman T. Noce C. Gardner J. Morat 《Engineering Geology》2007,89(3-4):278-299
We explore seismically-induced sand blows from the southern Mississippi Embayment and their implications in resolving the question of near or distal epicentral source region. This was accomplished using aerial photography, field excavations, and cone penetration tests. Our analysis shows that three sand blow fields exhibit a distinct chronology of strong ground motion for the southern embayment: (1) The Ashley County, Arkansas sand blow field, near the Arkansas/Louisiana state border, experienced four Holocene sand venting episodes; (2) to the north, the Desha County field experienced at least three episodes of liquefaction; and (3) the Lincoln–Jefferson Counties field experienced at least one episode. Cone penetration tests (CPT) conducted in and between the sand blow fields suggest that the fields may not be distal liquefaction associated with New Madrid seismic zone earthquakes but rather are likely associated with strong earthquakes on local faults. This conclusion is consistent with the differences in timing of the southern embayment sand venting episodes and those in the New Madrid seismic zone. These results suggest that active tectonism and strong seismicity in intraplate North America may not be localized at isolated weak spots, but rather widespread on fault systems that are favorably oriented for slip in the contemporary stress field. 相似文献
6.
The great 1950 Assam Earthquake revisited: Field evidences of liquefaction and search for paleoseismic events 总被引：1，自引：0，他引：1
D.V. Reddy P. Nagabhushanam Devender Kumar B.S. Sukhija P.J. Thomas Anand K. Pandey R.N. Sahoo G.V. Ravi Prasad K. Datta 《Tectonophysics》2009,474(3-4):463-472
Extensive field investigations were carried out for the first time in the meizoseismal area of the great 1950 Assam Earthquake aimed at exploring the paleoseismic history of the NE Indian region through documentation of liquefaction features and radiocarbon (14C) dating. Trenching at more than a dozen locations along the Burhi Dihing River valley and within the alluvial fans adjoining the Brahmaputra and Dibang Rivers resulted in the identification of more than a dozen very prominent liquefaction features (sand dykes, sills, sand blows etc.) as evidences of large to great earthquakes. 14C dating of the organic material associated with some of the features indicates a paleoseismic record of about 500 yrs archived by the sediments in this region. Compelling geological evidence(s) of the great 1950 earthquake are well constrained by 14C dating. Out of the two historically reported seismic events (1548 AD and 1697 AD) from this region, 14C dating could constrain the 1548 AD event though not distinctly. Further studies using combined 14C and OSL dating may better constrain the seismo-chronology of the study region. 相似文献
7.
The lack of earthquake-induced liquefaction features in Late Wisconsin and Holocene sediments in Genesee, Wyoming, and Allegany Counties suggests that the Clarendon–Linden fault system (CLF) did not generate large, moment magnitude, M≥6 earthquakes during the past 12,000 years. Given that it was the likely source of the 1929 M 4.9 Attica earthquake, however, the Clarenden–Linden fault system probably is capable of producing future M5 events. During this study, we reviewed newspaper accounts of the 1929 Attica earthquake, searched for earthquake-induced liquefaction features in sand and gravel pits and along tens of kilometers of river cutbanks, evaluated numerous soft-sediment deformation structures, compiled geotechnical data and performed liquefaction potential analysis of saturated sandy sediments. We found that the 1929 M 4.9 Attica earthquake probably did not induce liquefaction in its epicentral area and may have been generated by the western branch of the Clarendon–Linden fault system. Most soft-sediment deformation structures found during reconnaissance did not resemble earthquake-induced liquefaction features, and even the few that did could be attributed to non-seismic processes. Our analysis suggests that the magnitude threshold for liquefaction is between M 5.2 and 6, that a large (M≥6) earthquake would liquefy sediments at many sites in the area, and that a moderate earthquake (M 5–5.9) would liquefy sediments at some sites but perhaps not at enough sites to have been found during reconnaissance. We conclude that the Clarendon–Linden fault system could have produced small and moderate earthquakes, but probably not large events, during the Late Wisconsin and Holocene. 相似文献
8.
On June 23, 2001, an M8.4 earthquake that originated in southern Peru triggered the partial collapse of the Chislluma bofedal (water meadows) in the Altiplano (high-altitude plateau) of northern Chile. The seismic waves evidently produced the liquefaction of the bofedal and caused its partial collapse generating a flow. The flow deposit was mainly made of long-fiber grass and water, with minor amounts of clastic material. It traveled more than 14 km downstream at a peak velocity of 50 km/h. It destroyed the water meadows and killed more than 20 llamas. Slurry flows caused by meadow liquefaction are a previously unrecognized seismic-induced geological hazard for high-altitude plateau areas such as the Altiplano. 相似文献
9.
2018年5月28日,吉林松原市宁江区毛都站镇牙木吐村发生M5.7级地震(45°16'12″N,124°42'35″E),震源深度13 km,震中位于郯庐断裂带西北侧的扶余/松原—肇东断裂带、第二松花江断裂带和扶余北断裂带交汇处。地震诱发震中距3 km范围内普遍的液化和地表裂缝,给当地居民带来严重灾害。可见液化构造以砂火山为主,其次为液化砂堆、液化砂脉和液化砂席等。液化砂火山又可分为有火山口型砂火山、无火山口型砂火山和无砂型(水)火山。地震液化伴生软沉积物变形构造有变形层理、负载构造和火焰构造、滑塌褶皱、碟状构造和包卷层理等。地震诱发液化砂火山形成过程包括液化层内超孔隙流体压力形成、上覆低渗透层破裂和水、砂喷出地表后砂涌3个阶段。液化和流化砂体在上涌过程中会注入低渗透黏土层形成各种形态的砂脉、砂席和多种类型的变形构造。垂向上地震液化结构可划分为底部松散可液化层、下部液化变形层、上部液化变形层和地表砂火山4层结构。液化层埋深2~5 m,液化层厚度2 m。松原M5.7级地震发震机制为NE-SW(35°~215°)方向挤压应力使断层活跃,推测扶余/松原—肇东断裂是主要的发震断层。松原地震液化构造研究为现代地震活动区和灾害易发区预测提供依据,为地震引发的现代软沉积物变形构造研究提供丰富的素材,兼具将今论古意义,为揭示本世纪以来郯庐断裂带北段进入了一个强断裂和地震活跃阶段提供了最新的实际资料。 相似文献
10.
2010年玉树7.1级地震造成了一系列次生地质灾害。笔者在玉树灾区地震地质灾害调查基础上,结合Quickbird高分辨率遥感影像数据和航片影像数据,以目视解译为主,共提取了542处地震滑坡,并首次发现了11处古地震滑坡。调查研究结果显示,玉树地震滑坡主要包括崩塌、狭义的滑坡和土溜等三种类型。其中地震崩塌占到了90%以上,按其物质成分可进一步划分为碎屑型崩塌、碎屑流型崩塌和岩崩等三类。地震滑坡的空间展布特征显示,该区80%以上的地震滑坡集中分布在以玉树活动断层为轴的长约95km、两侧宽2km的廊带区内,并与发震断层距离和宏观震中有很好的相关性,其高密度区与同震地表破裂的空间分段性也有很好的对应关系,体现出典型的走滑型发震断层的控灾特点。同时,还进一步分析了山体坡度、坡体形态、临空面高度和地层岩石与岩体完整度等因素对地震滑坡总体分布的影响。对古地震滑坡的初步研究发现,古地震滑坡的规模、期次和分布特征间接地反映出玉树断裂带在全新世期间曾发生过多次震级强度明显大于本次玉树7.1级地震的古地震事件,这为更深入探索玉树断裂带古地震事件提供了另一种重要的研究途径。此外,地震滑坡分布与地表破裂和极震区破坏程度之间的密切空间关系指示,地震滑坡也可以成为快速圈定宏观震中以及开展极震区地震烈度评价等方面的重要指标。 相似文献