【摘要】 设以某个时间为起点至 t 时刻前的给定时段里,受统一构造应力场控制的大范围内的累积应变释放量为ε₀=1/C（?）,j 是全区地震总个数。在同一给定时段里,该范围内的第 K 个孕震区的累积应变释放量为（?）,m_k 是第 K 区地震总个数。其中,假定受统一构造应力场控制的大范围内,C 为常数;Ei 和 El 为相应的地震波能量。定义（?）为第 K 区在 t 时刻前夕的相对应变量。一次大震发生后,应力要重新调整,这必将引起一个地区应力系统的改变。我们希望有一个量来表明:在统一构造应力场控制下,这种调整、变化的特点。研究川滇地区1500年以来,M≥5.0级的地震活动表明,这一过程可以用相对应变量 P_k（k=1,2,…,9）来近似表达。自1917年以来,9个孕震区的共10次大震都发生在 P_k≤0.08的区里,而不发生在>0.08的区;对每个孕震区,P_k>0.08的期间是安全期,反之为危险期。这可作为川滇地震危险区的一个参考判据。更多还原

【Abstract】 In a given time interval from an initial value to time t, the accumulated strain releases in a large region controlled by a unified tectonic stress field are defined byj being the sum of earthquakes in the whole region.In the same time interval, the accumulated strain release of the kth preparing earthquake district within the region is:Where mk is the sum of earthquakes in the kth district.It is assumed that c is a constant for the large region controlled by unified tectonic stress field. Ei and Ei denote the corresponding energies of seismic waves. We defineand Pk is the strain ratio for the kth district in the large region just before the time t.the. stresses must be readjusted after a strong shock, so that it leads the change of the stress system in a large region. We expect to obtain a quantity showing the characteristics of this adjustment and variation under the restraint of unified tectonic stress field. Investigating seismic activity of M≥5.0 in Sichuan and Yunnan provinces since 1500, the process can be expressed approximately by relative strain quantities Pk ( = 1, 2,…, 9). Since 1917, the large earthquake occurred in the nine preparatory earthquake districts, which corre- sponds to the area of Pk ≤0.08. They are not found in area of Pk>0.08 This meas that the period of Pk>0.08 will be in safety to every preparatory districts. On the contrary, the period of Pk<0.08 will be danger. Thus, this would be a reference criterion of earthquake risk region in Sichuan and Yunnan provinces.更多还原