金沙江中游永胜昔格达层软沉积变形构造  

STUDY ON SOFT-SEDIMENTARY DEFORMATION STRUCTURES OF XIGEDA FORMATION IN YONGSHENG,MIDDLE REACHES OF JINSHA RIVER

作　　者：王莅斌 尹功明[1] 袁仁茂[1] 王盈 苏刚 WANG Li-bin;YIN Gong-ming;YUAN Ren-mao;WANG Ying;SU Gang(State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;China University of Geosciences,Beijing 100083,China;China Earthquake Disaster Prevention Center,Beijing 100029,China)

机构地区：[1]中国地震局地质研究所,地震动力学国家重点实验室,北京100029 [2]中国地质大学(北京),北京100083 [3]中国地震灾害防御中心,北京100029

出　　处：《地震地质》2020年第5期1072-1090,共19页Seismology and Geology

基　　金：中国地震局地质研究所基本科研业务专项(IGCEA1715);国家自然科学基金(41772185)共同资助。

摘　　要：在一定的地质环境中,地震可引起大范围的砂土液化和软沉积变形,所造成的破坏可能远大于地震震动直接造成的破坏。金沙江中游的永胜县涛源镇沿江分布有大面积的昔格达组湖相沉积物。同时,活动性强、地震频发的程海断裂带正好从永胜县涛源镇一带通过。在昔格达组未固结时,可能发生过1次强烈的地震触发了昔格达组的变形。基于研究剖面的变形特征分析认为:地震触发的大规模软沉积变形构造剖面中需存在砂层,下伏砂层、上覆黏土层的“二元结构”是地震触发软沉积变形构造的理想地层结构,且下伏砂层的厚度和变形强度决定了上覆黏土层变形强度;砂层中含有上覆黏土挤落的团块等非原层物质,砂层的上、下层面高低起伏不平;黏土层中的主要变形构造有地层错位、无根断层、砂层挤入、砂层管道、黏土层复杂褶曲、负载构造、火焰构造和肿缩构造等;变形构造样式复杂,无明显规律,且可形成大规模的强烈地层变形。The neotectonic movement in the middle reaches of the Jinsha River is active and the earthquakes occur frequently.Lacustrine sediments are commonly distributed on both sides of the river with stable sedimentary environment,good horizontal continuity and relatively developed stratification,which are good carriers for recording paleo-seismic events.In this study,a large number of soft sedimentary deformation structures are found in the riverside lacustrine sediments in the Taoyuan Town area in the middle reaches of Jinsha River,with strong deformation and large scale.We focus on the comprehensive analysis of four soft-sedimentary deformation profiles.In which the profiled strata are mainly medium-fine sand and clay.And the soft sedimentary deformation structures mainly include sand liquefaction,rootless faults,clay lumps and folds.Causes analysis:In the profiles of soft sedimentary deformation structures,there are medium and fine sand layers whose thickness is from thick to super thick.Sedimentary bedding has not been observed in the sand layer;and a large number of clay debris or lumps are involved in the sand layer,which are often filled between the adjacent clay lumps;and there are quicksand channels in the sand layer.All the features indicate that the sand layer in the study profiles has been liquefied.In the study profile,we found that the soft sedimentary deformation structure has the following characteristics:The faults found in the study profile extend downward and terminate in the lower liquefied sand layer and a large number of clay lumps.There are clay lumps in the place where the clay fold structure develops,and a large number of liquefied sand bodies are filled between the fold structures.The deformation structures in the profiles are not contrastive in terms of extension,chaotic deformation characteristics and obvious stress direction.Based on the characteristics of sand liquefaction and clay deformation in the above profile,it is inferred that the deformation structure in the profile is mainly due to

关 键 词：昔格达组 软沉积变形 古地震 金沙江中游 

分 类 号：P315.2[天文地球—地震学]