利用GPS研究红河断裂带及其邻区现今构造运动特征及其动力学意义

As a very important tectonic boundary in the southeastern margin of the Tibetan Plateau,the Red River fault has a long-term impacts on the tectonic evolution and the stratigraphic of its vast areas on both sides.It also plays an important regulating or conversion role in the collision of the Indian plate and Eurasian plate, the Tibetan Plateau uplift,the vigorous activity and deformation process of the faults and block.Moreover, the Red River fault live the strong earthquake activity. But in recent years, the seismic activities in the Red River fault zone and its adjacent area become weak relatively, why?The boundary effect of the fault become weaken? Or the fault has been in strong blocking state?However,due to the lack of observation data in the Red River fault ,we are still vague in its spatial and temporal heterogeneity ,segmentation and layered features,also the dynamic mechanism.In this study,we will systematically collect the histric GPS data of the Red River fault and its adjacent areas,cooperated with the new continuous and rover GPS data,the mobile observation data and the GPS profile data across the fault of different section.then process the data more refined to obtain a high-precision and high-resolution three-dimensional velocity field,also the time series of the baselines,and then measure the kinematics characteristics of all segments on the fault accurately (the fault slip rate and its movement characteristics,the stress distribution methods,the rotation and motion range of the adjacent blocks,etc.),On this basis,we will combine others geophysical observation datas to establish the finite element dynamic model, the ultimate aim is to study the meaning of the Red River fault in the absorption and conversion between the India - Eurasia plates convergence,and clarify why the Red River fault show weakening effect boundaries today , then provide evidence to the kinetic mechanism and potential seismic hazard assessment of the strong earthquake occurrence in the study area .

作为青藏高原东南缘一条重要的构造边界，红河断裂长期影响着两侧地区的构造演化和地层发育；在印度-欧亚板块碰撞、青藏高原隆升、断层及地块剧烈运动和变形过程中，起着重要的调节或转换作用。但近年来，红河断裂带及邻区地震活动较弱，是断层边界作用弱化？还是已处于强闭锁状态？由于观测资料的缺少，对红河断裂现今形变的时空不均匀性、分段分层特征、动力学机制等尚存疑义。本申请拟对红河断裂及邻区的历史GPS 资料系统整理，结合新增近场连续、流动观测及各分段的剖线资料，获取高精度、高分辨率三维速度场和时间序列；精确测定断层各段的运动学特征（滑动速率及运动特征、应力分配方式、相邻活动地块的旋转及运动幅度等），进而结合其他观测资料，建立动力学模型，从动力学角度研究红河断裂带在吸收、转换印度-欧亚板块汇聚中的作用，澄清红河断裂带现今表现出的边界弱化作用及其机理，为研究区强震发生的动力学机理和潜在的地震危险性评估提供佐。

本课题以密集的GPS 资料（陆态网络基准站、区域站GPS观测数据、新建跨红河断裂连续站等），深入研究并获取红河断裂不同分段、不同深度的滑动速率、闭锁程度以及构造应力积累速率，进一步确定红河断裂现今构造活动特征，并分析其成因；揭示研究区域动力学机制，分析现今构造运动格局的动力来源，从而深入理解并探讨红河断裂带强震发生的动力学机理和潜在地震危险性评估。主要研究内容及结果详述具体如下：.1）利用连续GPS资料论证红河断裂现阶段依然存在明显的分段运动特征，且活动性由北向南逐渐递减，北段5mm/a左右，而中、南段仅0.3mm /a；.2）利用GPS获取的跨红河断裂速度剖面揭示了断裂两侧运动速率表现为均匀的变化趋势，随距断层距离的变化并未出现运动速率的突变，表明跨红河断裂表现为连续变形的运动模式，同时结合红河及周边区域内部的均匀变形和应变，提出“红河断裂与周边断裂（南华-楚雄-建水断裂、无量山断裂等）可能是同一条超壳断裂在上地壳的不同分支”的假设；.3）充分研究红河断裂及其周边断裂的相互关系，研究结果表明：红河断裂东侧的南华-楚雄-建水-石屏断裂及西侧的澜沧江断裂、无量山断裂对红河断裂现今活动性影响显著；.4）结合历史地震的库仑应力影响、震间构造应力积累情况等对红河断裂全段进行了分析，发现历史地震同震及震后过程、震间构造运动在红河断裂中段形成应力影区，导致该地区地震发生率明显降低，一定程度地抑制了该地区地震的发生，并且这种影响还将继续持续一段时间；.5）对红河断裂所在的川滇菱形块体作为一个整体，对其形变特征及危险性进行分析研究，同时，对课题执行期间突发的九寨沟Ms7.0级地震，进行了深入研究，并构建基于GPS与InSAR约束的九寨沟Ms7.0地震滑动模型以获得川滇地区的现今构造特征及其地震危险性分析。