【摘要】 利用云南区域地震数字台网记录到的2005年8月5日云南会泽MS5.3地震和8月13日文山MS5.3地震的数字地震波形记录,在对S波观测记录位移谱进行传播路径、场地响应和仪器响应等校正后,根据B rune圆盘震源模型,利用遗传算法估算了这两个地震序列的震源参数。结果表明,两个序列的地震矩M0均在1012~1014N.m之间,与近震震级有很好的线性关系,与震源半径呈线性关系;应力降与近震震级无明显的依赖关系;拐角频率和地震矩之间有明显的依赖关系,但拐角频率的实际计算值cf与在给定地震矩条件下得到的估计值fa之差及应力降随时间的变化表现出了不同的特征:会泽地震序列的拐角频率差值和应力降在ML3.1余震前有一个由高到低的变化过程,反映了余震区应力场增高—下降的过程;文山地震序列拐角频率差值和应力降在ML≥3.1余震前均会出现高值或低值异常。更多还原

【Abstract】 On August 5 and 13,2005 respectively occurred the Huize M_S5.3 and Wenshan M_S5.3 earthquakes in Yunnan.The Yunnan Regional Digital Seismic Network recorded them.By removing propagation,site and instrument effects from the displacement spectra of the S-wave recordings,we obtain the source parameters of the Huize and Wenshan earthquake sequences based on the Brune disc model and Genetic algorithm,namely,the seismic moment M₀,stress drop Δσ and corner frequency f_c.The results show that there is a good linear relation between M₀(10¹²-10¹⁴ N·m) and local magnitude M_L;between M₀ and rupture radius r is also a linear correlation;Δσ seems independent on M_L;f_c increases with M₀ decreasing.According to the f_c-M₀ relation,we can give estimated corner frequency f_a.As for the two earthquake sequences,their corner frequency differences（f_c-f_a） and stress drops vary with time differently.The Huize earthquake sequence shows the change from high value to low value before the aftershocks with M_L≥3.1,which reflects the process of the stress field in the aftershock region varying from increase to decrease;whereas,the Wenshan earthquake sequence has the feature of high value or low value before the aftershocks with M_L≥3.1.更多还原