A paleo-seismological study of the Dauki fault at Jaflong,Sylhet, Bangladesh: Historical seismic events and an attempted rupture segmentation model     

《Journal of Asian Earth Sciences》2014

A paleo-seismological study was conducted at Jaflong, Sylhet, Bangladesh, which is on the eastern part of the Dauki fault. The geomorphology around Jaflong is divided into the Shillong Plateau, the foothills, the lower terraces, and the alluvial plain from north to south. Because the foothills and lower terraces are considered to be uplifted tectonically, an active fault is inferred to the south of the lower terraces. This fault, which branches from the Dauki fault as a foreland migration, is known as the Jaflong fault in this paper. The trench investigation was conducted at the southern edge of the lower terrace. The angular unconformity accompanied by folding, which is thought to be the top of the growth strata, was identified in the trench. An asymmetric anticline with a steep southern limb and gentle northern limb is inferred from the back-tilted lower terrace and the folding of the gravel layer parallel to the lower terrace surface. The timing of the seismic event which formed the folding and unconformity is dated to between AD 840 and 920.The trench investigation at Gabrakhari, on the western part of the Dauki fault, revealed that the Dauki fault ruptured in AD 1548 (Morino et al., 2011). Because the 1897 great Indian earthquake (M ⩾ 8.0; Yeats et al., 1997) was caused by the rupture of the Dauki fault (Oldham, 1899), it is clear that the Dauki fault has ruptured three times in the past one thousand years. The timing of these seismic events coincides with that of the paleo-liquefactions confirmed on the Shillong Plateau. It is essential for the paleo-seismological study of the Dauki fault to determine the surface ruptures of the 1897 earthquake. The Dauki fault might be divided into four rupture segments, the western, central, eastern, and easternmost segments. The eastern and western segments ruptured in AD 840–920 and in 1548, respectively. The 1897 earthquake might have been caused by the rupture of the central segment.  相似文献   

History of Paleoseismic Activity Along the Hohhot Segment of Daqingshan Piedmont Fault in the Late Quaternary   总被引：1，自引：0，他引：1  

Ran Yongkang  Zhang Peizhen  Hu Bo  Guo Wensheng 《中国地震研究》2001,15(2):190-204

INTRODUCTIONTheDaqingshanpledmont扭nit Is an irllt,oltant active normal tsult In the active fault－depressionzone——Hetao ault－depression zone In the northern part of Ordos Block,North China．It lies in ENEdirection long the southern pledmont of Daqingshan Mountain,dips to south,and extends for 200 kmor。。The fault was formed In the Eocene and strongly activated In the Cenozolc．Its verticaldlspl。ement exceeds 2400 m since the Quaternary(Rese。h Group on Ordos Block,State…  相似文献   

海山的倾斜俯冲对上覆板块变形的影响     

李付成  孙珍  张云帆  徐子英  谢辉 《地球物理学进展》2012,27(4):1406-1415

伴随洋壳的俯冲,驼伏其上的海山会导致上覆板块的强烈变形.为解释该构造变形特征,本文运用物理模拟实验的方法,着重分析海山的斜向俯冲对上覆板块变形的影响,并将模拟结果与正向俯冲过程进行对比.实验结果显示:海山开始进入俯冲,前缘楔体的增生会被阻止,同时楔体被抬升并出现脱顶构造,未被海山破坏的楔体会出现后冲断层的激活,后冲断层轴平行于海山的俯冲方向.海山进一步俯冲,突起项部发育一系列张扭性质的微断裂和走滑性质的共轭断裂,尾随突起之后的楔体由于重力会产生正断层系统.比起正向俯冲,斜向俯冲过程中所产生的后逆冲体、海山两侧的叠瓦状逆冲推覆构造都出现不对称分布,断裂和微断裂束的走向不规则散开,后冲断层的轴向及海山俯冲过后在楔体上产生的凹槽的轨迹都不断斜向迁移,且凹槽两侧的地势不一致等.最后利用文中的物理模拟结果,很好的解释了马尼拉海沟中段俯冲构造的构造特征,同时对其他俯冲大陆边缘的构造解释具有指导意义.  相似文献   

Late Holocene tsunami traces on the western and southern coastlines of the Peloponnesus (Greece)   总被引：1，自引：0，他引：1  

Anja Scheffers  Dieter Kelletat  Andreas Vtt  Simon Matthias May  Sander Scheffers 《Earth and Planetary Science Letters》2008,269(1-2):271-279

Greece, in particular the western and southern parts close to the subduction zone of the Hellenic Trench, experiences strong earthquakes and subsequent tsunamis. Nevertheless, field evidence of tsunamis from the late Holocene is extremely rare. Our research along the coastlines of the western and southern Peloponnesus resulted in new findings of tsunami impacts in the form of clusters and ridges of large boulders and thick tsunamigenic sand layers encountered in vibracores. Many boulders contained attached marine organisms, which prove that they were transported from the foreshore environment against gravity by extreme wave events. The attached organisms, which have been dated by ¹⁴C-AMS, suggest that historical tsunami events of great energy occurred around 1300 cal AD. A wood fragment found at the base of tsunami deposits in a vibracore from Cape Punta was dated to ~ 250 cal AD.  相似文献   

马尼拉海沟1.4 ka B.P.以来浊流事件沉积及其成因机制^*          下载免费PDF全文

徐伟  刘晓航  刘猛  胡丽沙  徐景平  汪志文 《古地理学报》1999,24(3):449-460

浊流是远距离沉积物运输的一种重要方式,海底浊流广泛存在于海底峡谷或海沟。马尼拉海沟位于南海东北部,是一条正在活动的板块汇聚边界。独特的地理位置(亚热带—热带)和气候条件(台风频发),使得马尼拉海沟浊流频发,然而,现今对马尼拉海沟的浊流研究甚少。本研究通过对马尼拉海沟北部水深3747 m处重力柱岩心(GEO6)进行高精度的粒度及沉积学特征分析,探讨马尼拉海沟浊流沉积规律。GEO6岩心底部细颗粒沉积物中浮游有孔虫的¹⁴C的AMS年龄为1405 a B.P.。高精度的粒度分析(0.25 cm)和沉积学特征显示: GEO6岩心记录有至少11次浊流沉积(T1-T11),且这些浊流都有明显的底部粒度最粗(砂质粉砂或砂)、向上粒度逐渐变细的正粒序特征,只有T8沉积体为反粒序特征,可能为异重流沉积。结合区域地质资料,本研究认为1.4 ka B.P.以来,研究区频繁的台风带来了大量陆源松散沉积物堆积在马尼拉海沟上游(高屏峡谷),不稳定的构造环境及地震频发导致这些松散沉积物垮塌并向下游马尼拉海沟输送,在海沟内形成频繁发育的浊流沉积体。  相似文献   

EFFECT OF TSUNAMIS GENERATED IN THE MANILA TRENCH ON CHINA MAINLAND          下载免费PDF全文

SHI Feng  HE Hong-lin  ZHOU Ben-gang  WEI Zhan-yu  BI Li-si 《地震地质》2018,40(3):579-589

Tsunami is one of the most devastating natural coastal disasters. Most of large tsunamis are generated by submarine earthquakes occurring in subduction zones. Tsunamis can also be triggered by volcano eruptions and large landslides. There are many records about "sea-overflow" in Chinese ancient books, which are not proved to be tsunamis. Tectonics and historical records analysis are import to forecast and prevention of tsunami. Consider the tectonic environment of the China sea, the possibility of huge damage caused by the offshore tsunami is very small. And the impact of the ocean tsunami on the Bohai sea, the Yellow sea, and the East China sea is also small. But in the South China Sea, the Manila subduction zone has been identified as a high hazardous tsunamigenic earthquake source region. No earthquake larger than M_W7.6 has been recorded in the past 100a in this region, suggesting a high probability for larger earthquakes in the future. If a tsunamigenic earthquake were to occur in this region in the near future, a tragedy with the magnitude similar to the 2004 Indian Ocean tsunami could repeat itself. In this paper, based on tectonics and historical records analysis, we have demonstrated that potential for a strong future earthquake along the Manila subduction zone is real. Using a numerical model, we have also shown that most countries in the South China Sea will be affected by the tsunamis generated by the future earthquake. For China, it implies that the maximum wave height over 4.0 meter on China mainland, especially the Pearl River Estuary. But the island, local relief maybe influence the maximum wave. But it takes nearly 3 hours to attack China mainland, if there is the operational tsunami warning system in place in this region, should be greatly reduced losses. And the simulated results are conformable to historical records. It indicates that the tsunami hazards from Manila trench to China mainland worthy of our attention and prevention.  相似文献   

2015年3月新不列颠M_S7.4地震震源及邻区构造应力场特征          下载免费PDF全文

崔华伟  万永革  黄骥超  李祥  高熹微  闫睿 《地球物理学报》2017,60(3):985-998

2015年3月30日至5月15日,巴布亚新几内亚-新不列颠地区发生了一系列地震.为研究该地区的构造应力环境及孕震背景,本文基于Global CMT目录,对新不列颠区域浅部进行构造应力场反演,拟得到高精度的应力图像.反演结果显示：（1）沿着南、北俾斯麦块体边界的区域构造应力场呈走滑体系,最大主压应力轴方位呈SWW-NEE向.（2）所罗门海的NW和NE走向的海沟处于压缩状态,所罗门海块体向新不列颠和所罗门群岛俯冲的板块弯曲部分是局部拉张.（3）受俯冲带的北向推挤,南俾斯麦板块顺时针旋转的挤压,太平洋板块向西部运动汇聚作用,新不列颠岛东北部与新爱尔兰岛南部交汇区域呈现明显非均匀应力状态.（4）此次地震序列的大多数走滑型和逆冲型地震,可能是所罗门海块体俯冲运动,和南俾斯麦块体与太平洋板块的近EW向挤压作用共同引发.  相似文献   

日本海沟俯冲带M_W9.0地震震源区应力场演化分析          下载免费PDF全文

杨佳佳  张永庆  谢富仁 《地球物理学报》2018,61(4):1307-1324

于2011年3月11日发生在日本东北部的M_W9.0级逆冲型板间地震是日本有地震记录以来震级最大的一次地震.本研究基于NIED F-net矩张量解目录中的震源机制解,选取两个长轴相互垂直的矩形区域进行应力场2D反演,获取了日本海沟俯冲带地区应力场的空间及时间分布图像.结果表明：主震前,俯冲带地区应力状态在空间上大体趋于一致,即应力轴（P轴、σ₁轴及S_Hmax轴）系统性地倾向板块汇聚方向,P轴、σ₁轴倾角整体偏缓（<30°）,且远离震源区及日本海沟东侧区域内的应力轴倾角普遍大于主震震源区内应力轴倾角;主震前,受2003年5月26日在宫城县北部发生的M_W7.0地震影响,位于M_W9.0地震震源区西北侧的应力场出现明显扰动,σ₁轴倾向顺时针偏转150°~180°,并于之后大体恢复至震前状态,同期其他地区没有明显变化,这种情况可能和主震断层局部（深部）的前兆性滑动有关;主震后,距离震源区较远处应力场变化不大,主震震源区内应力场发生显著改变,P轴及σ₁轴均以大角度（>60°）倾伏于板块汇聚方向,S_Hmax轴顺时针偏转60°~90°且在日本海沟附近普遍平行于海沟轴.这项研究以时空图像的方式展示了大地震前应力场变化的特点,反映了大地震孕震过程中构造与地震的相互作用,对于理解大地震孕震过程有重要意义.  相似文献   

马里亚纳海沟万米级水文观测研究     

马克  陈朝晖  李卓然  宋振杰  袁志伟  武斌  焦强  王志民 《海洋与湖沼》2021,52(5):1075-1087

深渊观测是开展深渊科学研究的前提。文章介绍了2020年7月"东方红3"船在马里亚纳海沟"挑战者深渊"附近完成的一次海洋调查。基于船载温盐深综合剖面测量系统获取的万米级剖面数据,分析全海深的温盐性质,并依据Thorpe尺度方法和细尺度参数化方法,进一步估算不同深度层的湍动能耗散率。结果表明:"挑战者深渊"的深层海水十分稳定, 3 000—5 000 dbar的温盐特征与下层绕极水相同;受弱层结背景下的内潮影响, 5 000—8 000 m的耗散率显著提升。本次调查获取的万米级水文剖面为马里亚纳海沟的深渊探索提供了数据方面的支撑。  相似文献   

The Research of the Activity of the Piedmont Fault on the Tangshankou Segment of the Yuguang Basin Southern Marginal Fault     

Wang Lin  Tian Qinjian  Li Dewen  Zhang Xiaoliang 《中国地震研究》2017,31(4):527-537

The Yuguang basin is a half-graben basin in the basin-range tectonic zone in northwest Beijing, located at the northern end of the Shanxi graben system, and the Yuguang basin southern marginal fault (YBSMF) controls the formation of this basin. A linear fault escarpment has formed in the proluvial fan on the piedmont fault zone of the Tangshankou segment of YBSMF. A trench across this escarpment reveals three paleo-earthquake events on two active faults. One fault ruptured at about 9ka for the first time, and then faulted again at about 7.3ka, causing the formation and synchronous activity of another fault. Finally, they faulted for the third time, but we cannot determine the faulting time due to the lack of relevant surface deposition. The accumulative vertical displacement of these three events is about 8.1m. We estimate that the average recurrence period of the piedmont fault is about 1.7ka, and the average slip rate of the piedmont fault is about 1.6mm/a. We also estimate the reference magnitude of each event according to the empirical formula.  相似文献