环境剪应力值τ_0的稳定性和预测效能分析

Stability and efficiency analysis of environment shear stress τ_0 for earthquake prediction

利用峰值加速度ap、峰值速度vp和峰值位移dp,计算了广东省河源地区64个地震的环境剪应力值0τ。结果表明,同一地震的0τa、τ0v、0τd可相差很大,0τv、0τd的误差主要来自地震矩M0。因此,如果不能从震源谱计算M0,则以峰值加速度方法计算0τ误差最小。剪应力值为使用震级序列分析地震趋势提供了明确的物理基础。即高震级地震多发说明应力场处于高强度背景,有发生更大地震的可能;反之则为低应力场背景,发生更大地震的可能性不大。公式分析和实际数据拟合得到lg(0τ)与ML有很好的线性相关,因此震级序列与剪应力值序列的地震预测效能是基本相同的。但与震级序列相比,0τ的计算显然要复杂,且误差也较大。

The environment shear stress τ0 for 64 smaller shocks form February 2002 to May 2003, recorded by Heyuan station, is calculated by using peak acceleration （αp）, peak velocity （vp） and peak displacement （dp）. We found that error of τ0v and τ0d mainly came from seismic moment M0. So, if M0 cannot be calculated from source spectrum, the error ofτ0, calculated by use of peak acceleration, was small. Shear stress provided the specific physical foundation for analyzing the earthquake tendency by use of magnitude sequence. When many shocks with high magnitude occurred, the stress field is situated in a reinforced background, which reminds possibility of lager earthquake occurrence, or vise verse. A linear correlation was got by means of formula analyzing and data fitting between lg（τ0） and ML. Therefore, the efficiency of earthquake prediction seems to be basically same when compared the magnitude with shear stress sequence. But the method of calculating τ0 is complicated, and its error probability is also higher than that of magnitude calculation.