藏东南及周边地区是印度板块与欧亚板块动力碰撞的影响区,该区历史地震活动强烈,曾发生过1950年墨脱-察隅8.6级和1951年当雄8.0级地震.本文首先介绍藏东南及周边地区的地质构造背景,其次通过考察该地区强震活动情况和活动地块边界带相关段落的加卸载响应比(LURR)时序特征,分析了研究区的强震活动状态.从历史地震活动看,安达曼弧地区与喜马拉雅东构造结地区强震活动存在一定的动力关联,当前研究区域的周边动力环境表现为安达曼弧地区地震活动强烈和东构造结地区的持续平静.从地震活动图像看,1980年以来6级以上地震在藏东南及周边地区已经形成空区,表现类似于1950年墨脱-察隅地震前的空间分布特征.从活动地块边界带相关段落LURR时序特征看,喜马拉雅带东段现处于高应力状态,其次为澜沧江带与三江带.%Southeastern Tibet and surrounding area is influenced by the dynamic collision between Indian plate and Eurasian plate, with strong historic seismic activity, including the 1950 Medog-Zayu M8.6 earthquake and the 1951 Dangxiong M8.0 earthquake. In this paper, we first presented the tectonic setting of Southeastern Tibet and surrounding areas firstly and then analysed the characteristics of seismic activity in this region by investigating activities of strong earthquakes and Load/Unload Response Ratio (LURR) time series of segments of the boundaries among active tectonic blocks. In view of the historical seismicity, we found a certain kinematical association between the Andaman arc and the eastern Himalayan system, and the current dynamic environment surrounding the study area is strong seismicly in the Andaman arc and seismicly quiescent in eastern Himalayan system.From the image of seismic activities, earthquakes with magnitude larger than or equal to 6.0 since 1980 have formed a circular seismic gap in southeastern Tibet and surrounding areas, whose spatial distribution is similar to that during the 10 years before the 1950 Medog-Zayu M8.6 earthquake. In terms of the LURR time series for segments of the active tectonic boundaries in the region, the eastern segment of Himalayan boundary is in the high stress state, followed by the Lancang River and Sanjiang tectonic boundaries.
展开▼
