论地幔波震级——CDSN应用系列论文四

DISCUSSION ON MAGNITUDE OF MANTLE WAVE

收集了1977—1990年间用 CMT 方法测定的地震矩 M_0和 NEIC 测报的面波震级 M_s 及1900—1976年间一些巨大地震的 M_0、M_s数据,得到 M_s与 lgM_0之间线性—非线性—M_s 最终达到饱和的图象。利用合理的地震运动学模型所相应的地震定标律可以深刻揭示该图象的物理本质。矩震级M_W 与特大地震的 M_s 趋势相一致,表征高于拐角频率时远场位移谱与地震矩 M_0之间的定量关系。本文基于面波的激发和传播理论,提出了测定地幔波震级 M_m 的新方案,并用 CDSN-LPZ 信道中的面波资料测定了1987—1990年间全球 M_s6.6以上浅源大地震的 M_m;同时对 Okal 和 Talandier(1989)的测定结果作了校正。结果表明,这样测定的地幔波震级与中小地震的 M_s 趋势相一致,表征低于拐角频率时远场位移谱与地震矩 M_0之间的定量关系。

This article collected the data of seismic moment M_0 determinated in 1977— 1990 by the CMT method and that of surface wave magnitude M_S reported by NEIC and the M_0, M_S data of some great earthquakes in 1900—1976.We have got the conception between M_S and lg(M_0) from linear, through non-linear to the final saturation of M_S.The physical meaning of the conception can be profoundly exposed by using the seismic scaling law corresponding to a reasonable seismic kinematic medel.The agreement of moment magnitude M_w and M_S of great earth- quakes show the quantitative relationship between far-feild displacement spectrum and seismic moment M_0 at frequencies higher than the corner frequency. This article provided a new method to determine the magnitude of mantle wave M_m based on the theory of surface stimulation and propagation, and deter- mined the M_m of the global earthquakes with M_S>6.6 of 1987—1990 by using the surface wave data of CDSN-LPZ channel, meanwhile it modified the M_m deter- minated by Okal and Talandier(1989). The result indicated that the magnitude of mantle wave obtained by this method is consistent with the tendency of M_S of medium and small earthquakes.This shows the quantitative relationship between the far-feild displacement spectrum and the seismic moment M_0 at frequencies lower than the corner frequency.