2001年云南施甸M_S5.9地震余震序列尾波Q_c值研究  

Study on the Q_c value of coda for sequence of aftershocks of Shidian M_S 5.9 earthquake in 2001 in Yunnan

作　　者：钱晓东[1] 李白基[1] 秦嘉政[1] 

机构地区：[1]云南省地震局,中国昆明650041

出　　处：《地震地磁观测与研究》2004年第1期9-17,共9页Seismological and Geomagnetic Observation and Research

基　　金：云南省重点科技攻关项目(NG2001);云南地区数字地震资料在短临预报中的应用方法研究

摘　　要：利用云南保山地震台记录到的 2001 年施甸地震数字化波形观测资料，根据尾波散射理论，测量了震源区尾波 Qc( f )值，结果表明，中心频率为 1.5 Hz 时，施甸地区尾波振幅衰减率 β(f ) 值在?0.012～?0.02 范围内，平均值为?0.017，Qc值在 110～140 之间，平均值为 124；得到施甸地区尾波 Qc值与频率的关系为 Qc( f ) = 77f 0.75 ；尾波波源因子 A0( f )与地震震级成正比，满足关系 lg A0( f ) = 0.899ML + 0.81，与频率成反比，满足关系 lg A0 = ?0.046 × f + 2.84 ；本文得到的一个重要结果是，施甸 5.3 级地震的最大强余震发生之前，Qc值存在一个变化过程；Qc值在均值附近 ±1.5 倍方差线内均匀地波动→Qc 值逐渐下降→Qc 值出现低于方差线的异常点→Qc 值逐渐恢复到正常水平→发震；施甸地区的尾波 Qc值不同于构造活动较为稳定的地区，而与构造活跃、地震活动频繁的地区较为接近，属于低频低 Qc值地区。According to the theory of coda dispersion, using the digital data recorded by Baoshan Station of Yunnan, the Qc value of coda at the source region has been estimated for the Shidian earthquake in 2001. The results show that the coda attenuation ratio β( f ) at Shidian region is in the range of –0.012～?0.02 and the average is –0.017 when center frequency f = 1.5 Hz. The Qc value of coda is in the range of 110～140 and the average is 124. It was obtained that the relationship is Qc( f ) = 77 f 0.75 between the coda Qc and the frequency f . The coda factor A0( f ) is direct proportion to magnitude: being satisfactory to lg A0( f ) = 0.899ML + 0.81, and inverse proportion to frequency: being satisfactory to lg A0 = ?0.046× f + 2.84 . An important result given by this paper is that Qc value possesses a evolution process before the strongest aftershock of Shidian MS 5.3: Qc value of coda uniformly undulate around within the ±1.5 times of variance→Qc value of coda decreases gradually→Qc value of coda is lower than that 1.5 times of variance→Qc value of coda increased and approached to the normal level→the earthquake occurrence. Qc value of coda in Shidian area is different to that stable tectonic environment and similar to that unstable tectonic environment as well as the frequent earthquake occurrence area. It belongs to low frequency and low A0( f ) value area.

关 键 词：地震余震 地壳Qc值 低值异常 尾波衰减 施甸地震 

分 类 号：P315.31[天文地球—地震学]