2014年2月12日新疆于田7.3级地震的震源参数

Research of source parameter of Yutian M_S7.3 earthquake in Xinjiang on February 12,2014

2014年2月12日新疆于田发生Ms7.3地震,本文利用新疆区域数字地震台网记录到的前震和余震序列的波形资料,对S波记录谱进行仪器响应、传播路径和场地响应的校正后,基于Brune模型,利用遗传算法反演了于田地震序列102次ML≥3.0级地震的地震矩、视应力、拐角频率等震源参数。结果表明,该地震序列震级为3.0~5.0级;地震矩为3.46×10^11~2.08×10^15N·m;视应力为1.48×10^5~1.16×10^6Pa,均值1.71×10^5Pa;拐角频率为1.4~7.1Hz。通过分析视应力及拐角频率随时间的变化特征可知,于田7.3级地震前震序列的视应力明显高于余震序列,而前震序列的拐角频率明显低于余震序列。主震前视应力出现高值,表明在主震区积聚了较多的应力,随后在应力值降低后的缓慢升高过程中发震,由于释放了大量的应力,震后视应力值又逐渐降低,表现为低应力的余震破裂。

The MS7. 3 earthquake occurred in Yutian,Xinjiang on February 12,2014. Based on seismic waveform data before the earthquake and aftershocks of the earthquake sequence,which were recorded by the Xinjiang Regional Digital Seismic Network,the paper corrected instrument response,propagation path and site response of the S-wave recording spectra. We then calculated with genetic algorithms,on the basis of the Brune model,the source parameters of 102 ML≥3. 0Yutian earthquake sequence,seismic moment,apparent stress and corner frequency. The results show that,seismic moment of the earthquake sequence is between 3. 46 × 10^11~ 2. 08 × 10^15,apparent stress is between 1. 48 × 10^5~ 1. 16 × 10^6,and mean stress level is 0. 31 MPa,and corner frequency is between 1. 4 ~ 7. 1Hz in the range of 3. 0 ~ 5. 0. By analyzing the apparent stress and corner frequency variation with time,we obtain that apparent stress of earthquakes before the Yutian MS7. 3 earthquake was significantly higher than the aftershock sequence,but the corner frequency was significantly lower than aftershock sequence. Apparent stress was high level before the mainshock,which shows the mainshock zone accumulated higher stress,and then the apparent stress reduced. The mainshock occurred in the process of slow increase. Because of the release of a large amount of stress,after the MS7. 3 earthquake,the apparent stress gradually reduced. That was the performance of low stress fracture of aftershocks.