利用EOF分析方法研究康定M_S6.3地震前后重力时空分布异常特征

Temporal and Spatial Distribution of Gravity Change before and after the Kangding M_S6.3:Using the EOF Method

对康定M_S6.3地震前后的流动重力观测数据采用正交经验函数(EOF)分析方法进行处理,分析主要模式与资料时段的M_S5.0以上地震震中位置的关系,探讨主要模式代表的物理含义。结果表明,川滇地区7期累积重力观测资料中大于200μGal的数据是偶然误差的概率大于95%。第二模式规格向量和累积重力变化均具有相似的分区特征,2013~2014年6次M_S6.0以上地震和第二模式规格向量正负转换带有超过83.3%的对应率,具备重力长期变化模式。第一模式地震前后规格值序列明显的同震信号、空间相似的4象限分布以及2014年4次M_S6.0以上地震和第二模式规格向量正负转换带100%的对应率表明,该模式代表重力短期变化模式。康定M_S6.3地震前第一模式包含4象限特点,震中位置规格值不断增大,且地震前后变化从负转为正。

We use the empirical orthogonal function （EOF） analysis method to analyze the Kangding Ms6.3 earthquake, the main mode and study period between the Ms5.0 earthquake above the epicen- ter, and we discuss the physical meaning of the main mode. The results show that in the normal dis- tribution fitting, there is agreater than 95 % probability of accidental error of gravity observation data that is greater than 200μGal of 7 phases of the Sichuan-Yunnan region. EOF analysis of the second model specification vector and the cumulative gravity changes have similar characteristics. The 6 earthquakes 〉Ms6.0 during 2013 to 2014 and the second model specifications vector positive and neg- ative conversion regions have more than 83.3% corresponding rate. This shows a long-term variation pattern in the gravity field. The first mode before and after the earthquake specification series is the coseismic signal, spatial similarity of 4 quadrant distribution and 4 earthquakes Ms〉6.0 in 2014 and the second mode vector specification of positive and negative conversion area of 100% corresponding rate, which indicates that the model of the region can represent short-term variations of the gravity model. EOF analysis method is used to study the temporal and spatial variations of the first mode and the normal vector of the Ganzi-Shimian section of the Kangding river before and after the Kangding Ms6.3 earthquake. The results show that the distribution of the 4 quadrants of the specification val- ues has already appeared in the latter half of the year. All the first mode results before the Kangding Ms6.3 earthquake are included in this feature. According to the characteristics of the constant increase of the epicenter location, the change is from negative to positive before and after Kangding earth- quake.