安徽淮河构造变形带及邻近块体现代构造应力场特征

针对安徽省较特殊的构造环境及历史地震分布特点，利用直达波最大振幅比和系统聚类分析方法，在对安徽淮河中游区1974年以来近百个中小地震震源机制反演、聚类及空间合成的基础上，分析了华北断块南缘的安徽淮河构造变形带及邻近块体震源断层滑动方式、构造应力场分布及块体运动方式、应力场随时间变化等。结果显示：淮河构造变形带及其邻近块体上震源断层总体上以近走滑型或斜滑型破裂为主，但倾滑型破裂也占一定比例；该地区构造应力以水平作用为主，但也存在一定的垂向作用。其中淮北和皖中块体仍可能分别向SWW和NEE方向运动，并在淮河构造变形带上产生左旋剪切作用，呈现一定的继承性活动特征；各块(带)上主压应力P轴走向随时间的变化在总体上较为一致，而各时段之间P轴方位存在一定差异，显示安徽淮河中游区受华北和华南应力场的共同作用，但其地震活动可能主要受控于华北应力场。

The Characteristics of Modern Structure Stress Field in the Huaihe Structure Deformation Belt,Anhui and Its Neighborhood Block

In this paper, aim at more special structure circumstance and the distribution characteristics of historical earthquakes in Anhui Province, using maximum amplitude ratio of the first arrival wave and the system clustering method, and based on the focal mechanism inversion, clustering and space composition to about 100 moderate-small earthquakes since 1974 at the middle Huaihe area, the authors analyse the slip model of focal fault, distributing of structure stress field, block movement mode, the variety of the stress field with time. It shows that the focal faults movement is mainly strike-slip or side-slip type in the Huaihe structure deformation and its neighborhood block, but there are certain quantity dip-slip type focal faults. The direction of structure stress is mainly horizontal in this area, but there is vertical structure stress. Among them, the Huaibei block moves toward SWW direction, the middle-Anhui block moves toward NEE direction and in the Huaihe structure deformation belt, the faults movement may be left-lateral shear; it presents inheritable characteristic. The changes of the direction of principal compressive stress P axes with time in each block are more consistent, but each period is different. It shows that the middle Huaihe area is controlled by the stress field of North China and South China, but its earthquake activity is mainly controlled by the stress field of North China.