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本文根据在近震源条件下,利用Brune模式,由昆明数字遥测地震台网观测到的波形资料,测定了2005年1月至2007年5月期间滇西南地区98次ML≥2.5地震的震源动力学参数,分析了在2007年6月3日云南泞洱MS6.4地震前视应力和拐角频率的时空变化特征。泞洱MS6.4地震前,较高视应力(2.5×105 Pa以上)主要分布在红河断裂与无量山断裂之间,较低视应力(2.5×105 Pa以下)在空间的分布则显得较为分散、随机。较低的拐角频率(1.5Hz以下)集中分布在泞洱地震震中东北部的红河断裂与无量山断裂之间,随着频率的增大,分布范围逐渐向西南扩展,直到整个区域,较高的拐角频率(3.5Hz以上)则集中分布在泞洱地震震中西南部的区域内。从视应力和拐角频率的时间变化曲线看,泞洱MS6.4地震前滇西南地区视应力表现出了明显的升高变化过程;含ML3.6以上地震的拐角频率随时间的变化呈下降—上升—下降的复杂过程,ML<3.6地震的拐角频率呈趋势下降过程。
According to the waveform data observed by Kunming Digital Telemetry Seismic Network under the condition of near-source, using the Brune model, the focal dynamics of 98 ML≥2.5 earthquakes in the southwestern Yunnan Province from January 2005 to May 2007 were measured. Parameters, the temporal and spatial variations of apparent stress and corner frequency before the MS6.4 earthquake in Yunnan Province on June 3, 2007 were analyzed. Prior to the M8.8 Ms6.4 earthquake, the higher apparent stress (above 2.5 × 105 Pa) was mainly distributed between the Honghe fault and the Wuliangshan fault, and the distribution of the lower apparent stress (below 2.5 × 105 Pa) was more dispersed in space ,random. The lower corner frequency (below 1.5 Hz) is concentrated between the Honghe fault and the Wuliangshan fault in the northeast of the epicenter of the Müer’er Earthquake. As the frequency increases, the distribution gradually expands to the southwest until the entire area is relatively high The corner frequency (above 3.5 Hz) is concentrated in the area southwest of the epicenter of the Murry-Erh Earthquake. From the time curve of visual stress and corner frequency, the visual stress of southwestern Yunnan showed a significant increase before MS6.4 M8.8 earthquake. The corner frequency with ML3.6 above earthquakes decreased with time - Ascending / descending complex process, the corner frequency of ML <3.6 earthquakes showed a tendency to decline.