小江和曲江-石屏两断裂系统相互作用的动力学模拟研究

In order to understand the dynamic mechanism, response and presentation form of faults interaction between different boundary belts of active blocks, we take the Xiaojiang fault zone and Qujiang-Shiping fault zone as an example to carry out research, which belong to southeast boundary and south boundary of Sichuan-Yunnan block, respectively. Integrating the information of geological and geophysical discipline, the 3D tectonic model of Xiaojiang fault zone and Qujiang-Shiping fault zone will be built. Based on the long historical earthquake sequences, we use viscoelastic model to analyze the persistent influence of coseismic impulse and postseismic viscoelastic relaxation on accumulated Coulomb stress and strong earthquake activities, about different fault segments of the whole fault system. With the help of numerical simulating, we use the model constrained by present surface deformation observation, to analyze the influence caused by different motion states of different fault segments on the regional deformation and strain partition. Combining the results above, we want to reveal the interaction pattern and dynamic mechanism between the main fault systems of active blocks’ adjacent boundaries. Because most of the strong earthquakes in Chinese mainland had occurred in the boundary zones of active blocks, our research results not only help to understand the gestation and occurrence mechanism of continental strong earthquakes, but also provide the important reference to the objective estimation of the seismicity trend in the main seismic tectonic belts.

为了认识活动地块不同边界带断层相互作用的动力学机制、响应与表现形式，本申请以川滇活动地块东南边界的小江断裂带以及南边界的曲江-石屏断裂带为例开展研究。综合地质与地球物理等多学科资料建立小江断裂带、曲江-石屏断裂带深-浅构造三维模型；基于较长历史地震序列并借助粘弹介质模型方法，分析强震同震及震后粘滞松弛效应对断层系统不同段落累积库仑应力及强震活动的持续作用；以现今地表形变观测资料为约束，利用数值模拟等方法手段分析各断层段不同运动状态对区域变形及应变分配的影响。综合上述分析揭示活动地块相邻边界带上主要断裂系统间的相互作用模式及动力学机制。由于中国大陆绝大多数强震均发生在活动地块边界带，因此研究成果不仅有助于了解大陆强震孕育及发生机理，更可为主要地震构造带的强震活动趋势客观研判提供重要参考。

为了认识活动地块不同边界带断层相互作用的动力学机制、响应与表现形式，本项目以川滇活动地块东南边界的小江断裂带以及南边界的曲江-石屏断裂带为例开展研究。在研究区内主要活动块体活动特征分析的基础上，开展了汶川地震同震位错模型的反演，并以震后GPS观测为约束模拟确定了青藏高原和华南地块的壳幔粘弹结构，作为动力学模拟的重要介质模型基础。以GPS速度场为约束反演确定了主要断裂带变形分布，讨论了断裂间的相互影响，为2021-2030年中国大陆地震重点危险区确定提供了重要基础。通过收集整理和补充计算构建了区域历史强震破裂模型集，并通过考虑同震和震后效应分析获得了断裂带间强震相互影响关系。通过综合分析断裂带上库仑应力累积状态以及基于速率-状态摩擦本构律模型的概率计算结果，对区域未来强震危险性做出了评估。由于中国大陆绝大多数强震均发生在活动地块边界带，因此研究成果不仅有助于了解大陆强震孕育及发生机理，更可为主要地震构造带的强震活动趋势客观研判提供重要参考。