山东乳山震群重复地震P波频散衰减特征分析

Analysis on P-wave dispersion and attenuation characteristics of repeating earthquakes of the Rushan earthquake swarm,Shandong Province

利用波形互相关方法识别乳山震群中的重复地震,挑选一组在时间上跨越2015年5月22日M_(L) 5.0地震的重复地震序列(repeating earthquake sequences,RES),利用测算单台直达P波第一个周期信号频散衰减特性的方法,估算乳山震群震源区介质品质因子,结果显示,不同路径下Q_(m)值随时间的变化形态基本一致,即此次M_(L) 5.0地震前Q_(m)值升高,临震及震后Q_(m)值下降并恢复至震前水平。同时,通过对震源区近场及远场应力状态的相关性分析,认为此次M_(L) 5.0地震发生在远场作用下区域构造应力状态调整过程中,与区域构造的介质状态、断层分布、速度结构密切相关。

In this paper,we identified repeating earthquakes of the Rushan earthquake swarm in Shandong Province by using the waveform cross-correlation method and searched out a group of repeating earthquake sequences(RES)that spanned the M_(L) 5.0 earthquake on May 22,2015.The medium quality factor of the focal area of the Rushan earthquake swarm is estimated by the method of calculating the dispersion and attenuation characteristics of the first period signal of direct P-wave of a single station.The results show that the shape of Q_(m) with time is basically the same under different paths,that is,the Q_(m) value increases before the M_(L) 5.0 earthquake,decreases before the immediate occurrence of the earthquake and after the earthquake,and recovers to the level before the earthquake.At the same time,according to the correlation analysis of the near-field and far-field stress in the focal area,it is considered that the M_(L) 5.0 earthquake occurred in the adjustment process of the regional tectonic stress under the far-field,which is closely related to the medium state,fault distribution and velocity structure of the regional structure.