RUPTURE CHARACTERISTICS OF LATE QUATERNARY STRONG EARTHQUAKES ON THE WESTERN BRANCH OF THE XIAOJIANG FAULT ZONE          下载免费PDF全文

LI Xi  RAN Yong-kang  WU Fu-yao  MA Xing-quan  ZHANG Yan-qi  CAO Jun 《地震地质》2018,40(6):1179-1203

The Xiaojiang fault zone is located in the southeastern margin of the Tibetan plateau, the boundary faults of Sichuan-Yunnan block and South China block. The largest historical earthquake in Yunnan Province, with magnitude 8 occurred on the western branch of the Xiaojiang Fault in Songming County, 1833. Research on the Late Quaternary surface deformation and strong earthquake rupture behavior on the Xiaojiang Fault is crucial to understand the future seismic risk of the fault zone and the Sichuan-Yunnan region, even crucial for the study of tectonic evolution of the southeastern margin of Tibetan plateau. We have some new understanding through several large trenches excavated on the western branch of the Xiaojiang fault zone. We excavated a large trench at Caohaizi and identified six paleoseismic events, named U through Z from the oldest to the youngest. Ages of these six events are constrained at 40000-36300BC, 35400-24800BC, 9500BC-500AD, 390-720AD, 1120-1620AD and 1750AD-present. The Ganhaizi trench revealed three paleoearthquakes, named GHZ-E1 to GHZ-E3 from the oldest to the youngest. Ages of the three events are constrained at 3300BC-400AD, 770-1120AD, 1460AD-present. The Dafendi trench revealed three paleoearthquakes, named E1 to E3 from the oldest to the youngest, and their ages are constrained at 22300-19600BC, 18820-18400BC, and 18250-present. Caohaizi and Ganhaizi trenches are excavated on the western branch of the Xiaojiang Fault, the distance between them is 400m. We constrained four late Holocene paleoearthquakes with progressive constraining method, which are respectively at 500-720AD, 770-1120AD, AD 1460-1620 and 1833AD, with an average recurrence interval of 370~440a. Large earthquake recurrence in the late Holocene is less than the recurrence interval of~900a as proposed in the previous studies. Thus, the seismic hazard on the Xiaojiang Fault should be reevaluated. We excavated a large trench at Dafendi, about 30km away south of Caohaizi trench. Combining with previous paleoseismological research, it is found that the western branch of Xiaojiang Fault was likely to be dominated by segmented rupturing in the period from late of Late Pleistocene to early and middle Holocene, while it was characterized by large earthquakes clustering and whole segment rupturing since late Holocene.  相似文献   

ESTIMATING THE WENCHUAN EARTHQUAKE RUPTURE PROCESS USING NEAR FIELD STRONG MOTION RECORDS AND COSEISMIC DISPLACEMENTS          下载免费PDF全文

YIN De-yu  LIU Qi-fang  LIU Chang  JI Xin-yang 《地震地质》2018,40(3):698-717

Based on the extensive near field broadband strong-motion records with uniform azimuthal coverage and coseismic displacements, the rupture process of 2008 Wenchuan earthquake is inversed by the non-negative least square method and multiple-time window technique. The possible rupture sequence among southern Beichuan Fault, Pengguan Fault and Xiaoyudong Fault and the initial rupture time of high dip angle part of southern Beichuan Fault are analyzed from kinetic aspects, which have been seldom focused on. The results indicate that:(1) The near field waveform fitting residuals and the coseismic displacements show that only a bilateral rupture occurs on the intersection between the southern Beichuan Fault and Xiaoyudong Fault can the synthetic records of the stations located near the southwestern end of the Beichuan Fault conform to the observed ones, and meanwhile, the Pengguan fault cannot generate large slips on its southwestern part. The possible rupture sequence is that the earthquake started at the low dip angle part of Beichuan Fault and propagates to the Pengguan Fault in the shallow area, the Xiaoyudong Fault is triggered by the Pengguan Fault, and then producing bilateral rupture on the high dip angle part of Beichuan Fault at the intersection with the Xiaoyudong Fault. (2) Through analysis of the synthetic second packet records of stations at the southwest area of the fault, we obtain the initial rupture time on the high dip angle part of Beichuan Fault may have a 8s stagnation. In terms of timing, there may be rupture sequence between the southern Beichuan Fault and Pengguan Fault which are parallel to each other. The rupture of the southern shallow part of Beichuan Fault with high dip angle may lag behind the Pengguan Fault. At the same time, there may be a multipoint rupture in the southern section of the Beichuan Fault. (3) There is a good correspondence between the area on the fault with larger slip rate and the surrounding stations with larger PGV. In areas where slip rate on the fault plane is large, the stations tend to have larger peak ground velocities.  相似文献   

基于震源-河谷波场数值模拟的坝址地震动参数确定方法   总被引：3，自引：0，他引：3       下载免费PDF全文

贺春晖  王进廷  张楚汉 《地球物理学报》2017,60(2):585-592

针对目前高坝坝址地震动参数确定方法的一些不足,本文尝试了一种基于地震学理论的坝址区三维地震动场生成方法.基本思路是将地震学和工程学结合,针对设定地震,建立震源-传播介质-坝址峡谷场地数值模型,通过超大规模的数值计算,模拟地震波从发震断层破裂开始到坝址场地的物理传播过程,生成坝址区的三维地震动参数.与传统基于衰减关系的地震动参数确定方法相比,这一方法可以考虑震源机制、传播介质和坝址峡谷场地效应等三大要素的影响.对于特定的坝址,可以生成符合实际地质构造、区域岩体动力特性以及坝址峡谷地质地形条件的地震动荷载分布,具有针对性,为重大高坝枢纽工程遭遇极端地震荷载作用时的抗震安全性提供了一种新的分析手段.  相似文献   

近断层地震动的基本特征   总被引：54，自引：11，他引：43  

刘启方  袁一凡  金星  丁海平 《地震工程与工程振动》2006,26(1):1-10

本文对近断层地震动的基本特征作了详细分析,这些基本特征主要包括近断层强地震动的集中性、地表破裂、地面永久变形、破裂的方向性效应、近断层速度大脉冲和上盘效应。这些特征虽然在一次地震中不一定同时出现,但它们是已经被强震观测资料和数值模拟证实了的,在模拟和预测近断层地震动时,必须充分考虑这些特点,合理的近断层地震动模拟或预测模型和方法应当在结果中再现这些特点。  相似文献   

有关1976年唐山地震发震断层的讨论   总被引：3，自引：1，他引：2       下载免费PDF全文

江娃利 《地震地质》2006,28(2):312-318

对《地震地质》刊登的两篇文章中有关唐山断裂是高角度西倾的逆冲走滑断裂及唐山市东侧付庄-西河断裂是唐山地震的发震断裂的观点进行讨论。笔者认为,如果唐山地震断层是西倾的逆冲走滑活动,需要考虑唐山逆冲断裂的活动方式与唐山市西侧第四纪凹陷之间的关系;如果付庄-西河断裂是唐山地震震源构造的地表破裂,需要解释该西倾的倾滑断裂带与唐山市内走滑地裂缝带的成因联系。此外,还需要更有说服力的证据排除该地表破裂带是次生构造破裂的可能。建议对控制草泊第四纪凹陷的活动断裂开展调查  相似文献