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以昆明数字地震台网对2001年4月12日施甸MS5.9地震序列观测的近300次地震事件的波形数据资料为基础,用横波波谱资料估算了该次地震序列的震源参数.结果表明,震级在1.5～5.3的范围内,地震矩范围为1010～1016N·m,拐角频率的范围为0.2～8.0Hz,震源破裂半径a的范围为200～2500m,地震应力降的范围为0.1×105～20×105Pa.通过对地震震源拐角频率fc及地震应力降Δσ随时间变化的统计分析,本文研究结果发现,施甸5.9级主震前的前震序列地震的平均拐角频率明显低于主震后余震序列的平均拐角频率.与之相反,地震平均应力降Δσ则是前震序列明显高于余震序列.分析认为,主震前后平均拐角频率和应力降的这种随时间变化特征,具有强震前的前兆信息指示意义.主震的前震序列具有高应力降显示出主震区储存了较高的剪应力;主震后,由于释放了绝大部分应力,余震序列则表现为低应力破裂过程.
Based on the waveform data of nearly 300 seismic events observed by the Kunming MS5.9 earthquake sequence on April 12, 2001, Kunming Digital Seismic Network estimates the source parameters of this earthquake series by using the shear wave spectral data , The magnitude is in the range of 1.5-5.3, the seismic moment range is 1010-1016N · m, the corner frequency range is 0.2-8.0Hz, the source rupture radius a is in the range of 200-2500m and the earthquake stress drop is in the range of 0.1 × 105 ~ 20 × 105Pa. Based on the statistical analysis of the frequency fc and the time-dependent change of the seismic stress drop Δσ over time, the results show that the average corner frequency of the pre-earthquake sequence before the Shidian M 5.9 Mistake is significantly lower than that of the main shock On the contrary, the mean earthquake stress drop Δσ is that the foreshock sequence is obviously higher than the aftershock sequence. The analysis shows that the average corner frequency and stress drop before and after the main shock with time variation features, with the pre-strong earthquake Indicates that the precursory information of the main shock has a high stress drop and shows a high shear stress which is stored in the main shock zone. After the main shock, the aftershock sequence shows low response due to the release of most of the stress Rupture process.