地震研究

通过计算1989年大同—阳高震群序列中5.7、5.9、5.6级3次地震的同震静态库仑应力,分析不同断层参数对库仑破裂应力的影响,并结合震群序列的分布和扩展方式,定量研究3次地震之间的触发关系。结果显示:5.7级地震可能是NW向左旋走滑,之后5.9级地震发生右旋走滑,震群活动为一组共轭剪切破裂的结果,并触发了后续地震。综合分析3次地震的时空分布与库仑应力变化的关系,推测1989年大同—阳高震群可能的发震机制为:①在区域应力场增强的背景下,2条共轭的发震断层均接近破裂临界水平,屈服应力较低的NW向团堡断裂先发生破裂; ②随后触发NE向大王村断裂破裂,且以NE向破裂为主,这与区域应力场方向一致; ③研究区域接收断层的有效摩擦系数比较高,在0.4以上; ④ 5.9级地震的发生,触发了西南区域的地震序列,东南区域的地震序列可能受5.9级地震的影响,并受控于断层的摩擦系数。总体而言,这3次M>5.5地震之间存在着一定的触发关系,5.9级地震对周边断层有明显的触发作用。

We calculated the co-seismic static Coulomb stress changes of the M5.7 earthquake,the M5.9 earthquake and the M5.6 earthquake in the 1989 Datong-Yanggao earthquake swarm,and analyzed the effects of different fault parameters on the Coulomb stress field,and quantitatively investigated the triggering relationships among these earthquakes by combining the distribution patterns of the aftershock sequences.The results show that the M5.7 shock may have been characterized by NW left-lateral strike-slip,followed by NE right-lateral strike-slip of the M5.9 shock,with conjugate activity of the seismogenic fault,and triggered the subsequent aftershocks.A comprehensive analysis of the distribution of events and the Coulomb stress changes suggests that the possible seismogenic mechanisms of the 1989 Datong-Yanggao earthquake swarm are:①In the context of the enhanced regional stress field,the 2 conjugate seismogenic faults were both close to the critical state of failure,and the NW-oriented Tuanbao fault ruptured firstly with lower yield stress; ②The NE-oriented Dawangcun fault was subsequently triggered rupture,and the NE-oriented rupture was predominant.The main aftershocks were distributed in NE direction,which was consistent with the direction of the NE principle compressive stress; ③The effective friction coefficients of the receiving faults in the study area were relatively high(over 0.4); ④The M5.9 earthquake triggered the aftershocks in the southwest region,and the aftershocks in the southeast region may be influenced by the M5.9 earthquake,and was controlled by the friction coefficient of the fault.Generally,there was a trigger relationship between the three M>5.5 earthquakes,and the M5.9 shock had a significant triggering effect on the surrounding faults.

引言
1 区域地震地质背景及震群分布
2 研究方法及参数选取
3 研究结果
4 讨论
5 结论

图1 1989年大同—阳高震群区域地质构造及地震序列分布<br/>Fig.1 The 1989 earthquake swarm and geological structures in Datong-Yanggao region

图1 1989年大同—阳高震群区域地质构造及地震序列分布
Fig.1 The 1989 earthquake swarm and geological structures in Datong-Yanggao region

图2 1989年大同—阳高震群活动随时间的变化<br/>Fig.2 The activity of the 1989 Datong-Yanggao earthquake swarm in the latitude direction along with time

图2 1989年大同—阳高震群活动随时间的变化
Fig.2 The activity of the 1989 Datong-Yanggao earthquake swarm in the latitude direction along with time

表1 1989年大同—阳高震群的3次地震的震中及破裂参数<br/>Tab.1 Parameters of the 3 large earthquakes in the 1989 Datong-Yangao sequence

表1 1989年大同—阳高震群的3次地震的震中及破裂参数
Tab.1 Parameters of the 3 large earthquakes in the 1989 Datong-Yangao sequence

表2 研究区介质模型参数<br/>Tab.2 Parameters of the medium models in the study area

表2 研究区介质模型参数
Tab.2 Parameters of the medium models in the study area

表3 1989年大同—阳高震群3次地震的震源机制解中心解<br/>Tab.3 Focal mechanism solutions for the 3 large earthquakes in the 1989 Datong-Yangao sequence

表3 1989年大同—阳高震群3次地震的震源机制解中心解
Tab.3 Focal mechanism solutions for the 3 large earthquakes in the 1989 Datong-Yangao sequence

图3 1989年10月18日22时—10月19日10时大同—阳高地震序列M-t图<br/>Fig.3 M-t of the Datong-Yanggao earthquake sequence from 22:00,October 18 to 10:00,October 19,1989

图3 1989年10月18日22时—10月19日10时大同—阳高地震序列M-t图
Fig.3 M-t of the Datong-Yanggao earthquake sequence from 22:00,October 18 to 10:00,October 19,1989

图4 1989年大同—阳高5.7级地震引起的5.9级地震接收断层库仑破裂应力变化<br/>Fig.4 Changes of Coulomb failure stress on the receiving fault of the M5.9 shock caused by the 1989 Datong-Yanggao M5.7 shock

图4 1989年大同—阳高5.7级地震引起的5.9级地震接收断层库仑破裂应力变化
Fig.4 Changes of Coulomb failure stress on the receiving fault of the M5.9 shock caused by the 1989 Datong-Yanggao M5.7 shock

图5 1989年大同—阳高5.9级地震NE向破裂面引起的5.6级地震接收断层库仑破裂应力变化<br/>Fig.5 Changes of Coulomb stress on the receiving fault of the 1989 M5.6 shock caused by the NE-oriented rupture of the 1989 Datong-Yanggao M5.9 shock

图5 1989年大同—阳高5.9级地震NE向破裂面引起的5.6级地震接收断层库仑破裂应力变化
Fig.5 Changes of Coulomb stress on the receiving fault of the 1989 M5.6 shock caused by the NE-oriented rupture of the 1989 Datong-Yanggao M5.9 shock

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备注

引言

1 区域地震地质背景及震群分布

2 研究方法及参数选取

3 研究结果

4 讨论

5 结论

期刊信息