b值和地震复发周期

针对过去计算b值的误差，提出了两条改进措施：（1）采用统一的绝对震级标度-矩震级标度MW；（2）舍弃缺失地震次数的点，然后用最小二乘拟合求得b值，使b值计算较准确. 据此，用3种不同来源和不同精度的资料计算，得到的b值都接近于1. 我们固定b值为0.85，用13年的现代地震观测资料，计算今后50～100年内较大地震（外推震级1～2级）的复发周期，结果表明，6级和7级以上地震的复发周期与用近100年的历史地震资料计算得到的复发周期相当一致，可以说外推的结果是可靠的.

b-VALUE AND EARTHQUAKE OCCURRENCE PERIOD

Two improvements measurements pointed to the errors to calculating b values have been proposed: (1) to adopt the uniform absolute magnitude scale, seismic moment magnitude MW, (2) to discard the magnitude points for which the earthquakes absent and lose, and then to compute the b value using least square method to fit the data. The b values obtained for three data sets of different precision and sources are close to 1.0 . The occurrence periods of great earthquakes for coming 50～100 year (extend 1～2 magnitude) have been computed using 13 years recent earthquake observation data and fix b=0.85. The results demonstrate that the earthquake occurrence periods with magnitude greater than and equal to 7 and 8 are well consistent with that calculated from the data of 100 years history earthquakes, implying the reliable extension.