苏皖地区2次中强地震前地下流体异常及其形成机理分析

Typical Underground Fluid Anomalies and the Precursor Mechanisms of Two Moderate Earthquakes in the Jiangsu and Anhui Regions

摘要:

归纳总结了安庆M_S4.8地震、高邮-宝应M_S4.9地震前出现的地下流体异常，并对其形成机理作了初步讨论。结果显示，这2次地震前地下流体异常特征比较相似。在时间进程上，都表现出中期趋势背景异常与短临异常的配套性特征。在空间分布上，中期趋势背景阶段，水位异常均表现为震中附近流体井水位呈趋势性转折上升，而震中外围流体井水位呈趋势性转折下降的特点。且转折上升的流体井在空间上的分布方位与地震的发震断层走向一致。在短临阶段，异常均表现为先向外迁移继而向震中靠拢的特点。水位在空间上的规律性分布可能受区域应力场作用以及区域构造格局所控制。

Abstract:

This paper summarized the typical underground fluid anomalies and discussed the possible mechanism of the Anqing M_S4.8 earthquake and the Gaoyou-Baoying M_S4.9 earthquake. The results show that the characteristics of the underground fluid anomalies before the two earthquakes are very similar. According to the duration time,both of them include medium-term trend anomalies and short-term anomalies. There is also certain regularity on spatial distribution. During medium-term stage,the water level of outlying wells shows a downward trend,and the water level of wells close to epicenter shows a rising trend. The distribution orientation of the water level with the rising trend is the same as the trend of the earthquake fault. During short-term stage,anomalies migrate far from the epicenter in the short-term stage first and migrate back close to the epicenter in the impending-term stage. The regularity distribution of the water level probably is controlled by the regional stress field and structure patterns.