地幔波震级的规范化标定与观测

本文基于瑞利面波的激发和传播理论,导出了零级地震的理论面波谱表达式;并以零级地震为参考地震,以零级地震所相应的面波谱和地震矩作为地幔波震级规范化标定的参照依据,进而提出了测定地幔波震级的新方案。利用CDSN-LPZ信道中的面波资料测定了1987—1990年间全球54次浅源大地震的地幔波震级M_m,并对Okal和Talandier(1989)用GEO-SCOPE-VLPZ及PAS-VLPZ信道中的基阶瑞利波所测1970—1987年间88次地震的结果作了校正。综合这两部分观测结果,得到M_m=1.00 1gM_0—12.13,由此测定的地幔波震级与中小地震的面波震级M_s趋势相一致,为解决面波震级饱和问题提供了一种可行的途径。

STANDARDIZATION CALIBRATION OF THE MANTLE WAVE MAGNITUDE AND OBSERVATIONS

The theoretical expression of spectral amplitudes of surface wave for the earthquake of magnitude zero has been derived from the theory of excitation and propagation of Rayleighwave in this paper.The earthquake of magnitude zero is selected as a reference earthquake,and the theoretical surface wave spectrum and seismic moment corresponding to the earthquake of magnitude zero are selected as the reference basis of standardization calibration for the mantle wave magnitude.A new scheme for determining the mantle wave magnitudes has been further proposed According to the new scheme,The mantle wave magnitudes Mm about 54 great shelloy earthquakes in the world from 1987 to 1990 have been determined using the surface wave data of CDSN-LPZ channel.The results of 88 great earthquakes from 1970 to 1987 determined by Okal & Talandier (1989) using the fundmental code Rayleigh waves of GEOSCOPE-VLPZ and PAS-VLPZ channel have been corrected.It is found from all these two data sets that Mm=1.001g M0 -12.13,which shows that the determined mantle wave magnitudes agree with the tendency of surface wave magnitudes Ms of median and small size earthquake.Thus the mantle wave method becomes a feasible approach for solving the saturation problem of the surface wave magnitudes.