地震力标度及其在华北地区的应用

Seismic Force Scale and its Application in North China

讨论了华北地区中强地震前地震力标度的时空变化特征,首先介绍了地震力标度的物理意义,给出了由传统经验公式推导出的地震力标度σ值的计算方法,σ值是一个表征地震时震源处断层平均驱动力的物理量,基于地震波能量推导得到,介于地震频度和能量之间,根据经典通用的经验公式,地震力标度σ值与震级ML存在lgσ=1.14 ML+6.22标度关系;结合华北地区(34°～42°N;110°～124°E;)地震活动的特点,利用1980年以来2500多次3级以上地震,研究了MS≥5.0中强震前σ值的变化规律,结果发现该指标能客观反映地震活动的增强与平静。中强地震前存在σ值高值异常,σ值有由低转高,在高值点发震的特征。空间上σ值的分布与地质构造、地震带和强震孕育过程有关,中强震前地震力标度σ值有成片增加的过程,对中强地震预测有一定的指导意义。

We discussed variation of seismic force scale in time and space before moderately strong earthquakes in North China. We first introduced the physical meaning of seismic force scale （σ value） and its calculation method has been derived by the traditional empiri cal formula. Based on seismic wave energy, σ value is a physical quantities of average driv ing force in the seismic source at the fault, which is between earthquake frequency and en ergy. It is derived that the seismic force scale a value and magnitude can be described as the relation of lgσ= 1. 14ML ＋6. 22. Combined with the seismic activity characteristics in north China （34°-42°N; 110°-124°E ）, using more than 2500 3,0 earthquakes, and value variations before Ms≥5.0 earthquakes then are studied. It is found that this indica tor can objectively reflect the enhanced and calm of seismic activity, with high σ value be fore moderately strong earthquakes. Spatial characteristics are related to geological structure, seismic zone and strong earthquake preparation process, earthquake force scale σ value has the characteristics of extensive increasing process.