从1786年磨西地震看地震地表破裂带在不同地貌区的保存  

PRESERVATION OF CO-SEISMIC SURFACE RUPTURE IN DIFFERENT GEOMORPHOLOGICAL SETTINGS FROM THE STUDY OF THE 1786 MOXI EARTHQUAKE

作　　者：陈桂华[1] 闵伟[1] 宋方敏[1] 焦德成[2] 许洪泰[3] 

机构地区：[1]中国地震局地质研究所,国家地震活动断层研究中心,北京100029 [2]宁夏回族自治区地震局,银川750001 [3]山东省地震局,济南250014

出　　处：《地震地质》2011年第4期804-817,共14页Seismology and Geology

基　　金：地震行业科研专项(200708029);国家重点基础研究发展计划项目(2004CB418401)共同资助

摘　　要：地震地表破裂是活动断裂填图的重要内容之一,晚第四纪地貌是保存地震地表破裂等活动断裂最新变形的基本载体,利用不同地貌全面获取断裂的活动信息非常重要。通过对鲜水河断裂带东南段进行野外填图、探槽开挖等调查,讨论了1786年磨西地震地表破裂在青藏高原冰川、冰缘地貌区和高原边缘的流水堆积和强剥蚀地貌区的保存特征。地震裂缝和断错等微地貌在高原冰川、冰缘地貌区记录保存完整。高原边缘的流水堆积具有强侵蚀和快速堆积等不稳定性,在探槽中可以获得不完整的地震地表破裂记录。而强剥蚀区缺少记录地震地表破裂的最新堆积地貌,只能依靠与地震动和断裂破裂具有间接关系的古滑坡等推测地震影响区和地表破裂范围。结合鲜水河断裂带东南段的几何结构和构造环境认为,鲜水河断裂带康定—田湾段是1786年地震的发震构造,该地震破裂长度约80km。The co-seismic rupture is one of the important contents in active tectonic mapping.As the late Quaternary landform is a basic recording medium for the recent deformation of active fault,such as the co-seismic rupture,it is quite useful to acquire the activity information of the active fault from various landforms.We implemented a field work along the southeastern segment of the Xianshuihe Fault,mapped the rupture and excavated some trenches.The preservation characteristics of the surface rupture of the 1786 Moxi earthquake were discussed for the glacial area of the Tibetan plateau,the fluvial and flooding area and seriously eroded area at the margin of the Tibetan plateau,respectively.The cracks and offsets were preserved continuously in the glacial landforms such as the moraines and glacial outwashes along Kangding to Yajiageng segment.As the landforms in the fluvial and flooding area were unstable under strong erosion and rapid deposition,the surface rupture can be discovered in the trenches excavated in Yuejinping village and Ertaizi village with gaps for some previous earthquakes.There was no deposition from the erosion landform to record the surface rupture.We can only infer the earthquake effected area and the ruptured fault from the indirect relationship between landslides and the earthquake strong motion or the fault rupturing.Based on the integrated analysis with the geometry and tectonic setting of the southeastern segment of the Xianshuihe Fault,the Kangding-Tianwan segment of the Xianshuihe Fault was taken as the seismogenic fault of the 1786 Moxi earthquake,and the total length of the rupture is about 80 kilometers.

关 键 词：地震地表破裂 剥蚀地貌 堆积地貌 1786 年磨西地震 

分 类 号：P312.5[天文地球—固体地球物理学]