江苏体应变数字台网地震尾波的衰减关系与震级

体积式应变仪能记录全球大震,根据江苏体应变数字台网记录的全球大震波形,给出了测定地震尾波衰减系数、台网震级公式、震级标准差以及单台校正值的方法。由衰减经验关系lgA=G-klgτ导出的地震尾波应变双振幅A随尾波推移时间τ的衰减系数k=1.415,并取得以M(PEK)震级为基准的地震尾波应变台网震级公式MDC=4.02+1.04lgτ+0.74lgA±0.02,给出了江苏5个体应变台站的震级校正值,计算了近年内全球发生的35个地震震级值,平均震级标准差为0.11。尾波多点测量改善了7.6级以上大震MDC的精度,用该方法测量全球大震不存在震级"饱和"问题。

Decay law and magnitudes of coda waves for the Jiangsu Digital Volumetric Strain Network

Volumetric strainmeters can record large earthquakes all over the world. Based on the waveforms of the large earthquakes all over the world recorded by the Jiangsu Digital Volumetric Strain Network, methods for determining the seismic coda's decay law, magnitude formula of the network, standard deviations of magnitudes and station correction values are given.Using these methods a value of 1.415 is obtained for the decay coefficient k in the empirical formula of lgA=G-klgτ, which characterizes the die away of the double amplitudes A of the seismic coda with the coda's elipse time τ(beginning from the P wave on a short period seismograph). The following expression is obtained as the coda wave magnitude formula for the strain network taking the M(PEK) magnitude as magnitude standard: MDC=402+104lgτ+074lgA±002. The station correction values of magnitude are given for the five volumetric strain stations in Jiangsu Province. The magnitude values are calculated for 35 earthquakes occurring all over the world in the recent several years with an average standard magnitude deviation of 011.The accuracy of MDC determination for great earthquakes of magnitude above 76 is improved based on the multipoint measurement of coda waves. No magnitude saturation problem exists when this method is used to determine the magnitudes of great earthquakes all over the world.