武定地震序列的震源参数与频率特征

Characteristics of source parameters and frequency of Wuding M S 6 5 earthquake sequence

利用武定地震序列数字化记录地震图资料研究了直接用速度谱和位移谱测定地震矩的方法，结果给出前者的误差比后者小５０％，两者无系统差。对序列地震震源参数的研究结果给出，地震矩Ｍ０在１０１２～１０１６（Ｎ·ｍ）之间，震源破裂半径ａ在１００～３５０ｍ范围，震源距ｒ或震级ＭＬ与近场波谱拐角频率ｆ０相关性不明显，序列地震应力降Δσ多数在１０～８０ＭＰａ的范围，表明武定地震序列是在高应力背景下发生的爆发性地震群。

In this paper,we have studied the methods of determining the seismic moment M 0 directly by using velocity spectra and displacement spectra obtained from digital seismic data of Wuding M S 6 5 earthquake sequence.The average standard error obtained from the velocity spectra model is 50% less than that obtained from the displacement model and no system error between two models.The results for the source parameters of the seismic sequence are that the seismic moment M 0 is between 10 12 N·m and 10 16 N·m,the rupture radius a of the source is between 100 m and 350 m,the dependence of the source distancer r or the magnitude M L on the corner frequency f 0 is unclear,and the stress drop Δ σ is mostly between 10 MPa and 80 MPa.These results show that Wuding M S 6 5 earthquake sequence is a paroxysmal seismic cluster occurred under high stress background.