安徽北淮阳构造变形带特征与应力状态研究

Research of the Bei-Huai-Yang structure deformation belt characteristic and modern stress state in Anhui Province

在分析安徽北淮阳构造变形带变形特征和活断层作用的基础上,利用该区现代中小地震资料,采用近震直达P波、S波垂直向最大振幅比方法、震源机制的系统聚类和统计分析法,反演部分地震震源机制,并分析现代中小地震活动特征及应力场状态。结果表明,北淮阳构造变形带上主要断层现今处于活动状态;现代中小地震震源总体较浅,在2次6级地震震中附近形成小震密集区,可能反映了震源区介质相对破碎。震源机制的系统聚类和统计分析结果显示,该区断层以走滑或斜滑型破裂为主,但存在倾滑的逆断层;区内应力作用方向以水平为主,也存在部分垂向力作用;主压应力P轴的优势分布为近EW向,其中既有华北应力场,也有华南应力场作用;有少量近NS向应力场作用存在。反映该区处于应力场过渡区,因此将其作为华北、南华地块区的边界是合理的。

Based on the analysis of Bei-Huai-Yang structure deformation belt characteristic and effect of the alive fault, using the data of modern moderate-small earthquakes, we inverse a part of focal mechanism parameter, and analyze the characteristic of moderate-small earthquakes and stress field state by uprightness maximum amplitude ratio of first arrival P-and S-wave and focal mechanism parameter system clustering and statistic analytical method. As results, the mostly fault in Bei-Huai-Yang structure deformation belt is in active;the source of more modern moderate-small earthquakes is shallow, and the distributing of earthquakes around the M6 epicenter is thick. It maybe reflects that the medium of the near focus is relatively cracked. The result of the focal mechanism parameter system clustering and statistical analysis shows that the fault in this area is mainly strike-slip or side-slip type and still some incline-slip retrorse fault;The direction of structure stress is mainly horizontal in this area, but there is vertical structure stress. The distribution of the P axis of the main press stress is about EW, it shows that the North China and the South China stress field control this area and it is transient area of stress field. So this belt maybe looks upon as boundary of North China and South China.