摘要
2022年6月10日马尔康M_(S)6.0震群序列发生在松岗断裂与龙日坝断裂交会处,呈震群型活动特征。本文以四川地震台网目录为基础,对马尔康地震序列的参数特征开展研究,取该序列三次M_(S)5.0地震之后各一个小时,作为Ⅰ,Ⅱ,Ⅲ共计三个阶段,进行对比分析。由于较大地震后短时间内目录遗漏的余震较多,为增大研究所需的地震样本量,首先采用模板匹配法进行微小地震识别,以补充完备目录,并利用识别的地震目录及台网目录分别计算马尔康M_(S)6.0地震序列的b值、p值等参数。计算结果显示,相比于第Ⅱ和Ⅲ阶段,第Ⅰ阶段具有显著的低b值(0.59),随着时间的推移,序列b值逐渐上升,后两个阶段分别为0.84和0.86。第Ⅰ阶段低b值的结果反映了此阶段孕震区应力水平较高。另外,第Ⅰ阶段序列的p值为0.76,明显低于后两个阶段的1.81和1.64,反映出第Ⅰ阶段序列频次衰减速度较慢,应力释放不充分,而后两个阶段刚好相反,表明不同阶段序列的时间演化特征存在差异。综合分析认为,M_(S)5.8地震是M_(S)6.0地震的前震。序列西支与东支的参数计算结果呈现不一样的特征,可能与M_(S)5.8前震序列发生在西支有关。
According to the China Earthquake Networks Center,at 00:03 on June 10,2022,local time,an earthquake with M_(S)5.8(M_(L)6.3)struck Barkam City(32.27°N,101.82°E),Aba Prefecture,Sichuan Province,with a focal depth of 10 km.Subsequently,at 01:28 local time,another M_(S)6.0(M_(L)6.5)earthquake occurred in the same location(32.25°N,101.82°E),with a focal depth of 13 km.These two earthquakes were located in the southeast part of the Bayan Har block,approximately two kilometers apart.According to the definition of earth-quake sequence type,the magnitude difference between the two earthquakes ΔM=0.2 consti-tutes a swarm type earthquake,which is hereinafter referred to as“M_(S)6.0 Barkam earthquake swarm”.The M_(S)6.0 Barkam earthquake swarm exhibited numerous minor earthquakes,up un-til 23:00 on June 30,2022,a total of 4821 earthquakes of magnitude 0 and above were recor-ded,including seven earthquakes with magnitude ranging from MS3.0 to M_(S)3.9,three earth-quakes with magnitude ranging from M_(S)4.0 to M_(S)4.9,two earthquakes with magnitude ran-ging from M_(S)5.0 to M_(S)5.9,and one M_(S)6.0 earthquake.The largest aftershock recorded was an earthquake with M_(S)5.2(M_(L)5.6)at 03:27 local time on June 10.Considering the significant event of an earthquake with M_(S)5.8 preceding the occurrence of the main shock with M_(S)6.0,it is important to investigate the characteristics of the M_(S)5.8 earthquake sequence as a foreshock and the sequence features before and after the main shock.Existing seismological methods in-dicate that earthquake sequences can intuitively reflect differences in tectonic stress fields,seis-mic structures,and the seismogenic environment medium.Moreover,the rupturing properties of the main shock often influence the evolution of aftershock sequences.This study utilizes seis-mic data from the Sichuan regional seismic network,based on parameters such as the b-value and p-value of the sequence,in combination with regional structure and focal mechanism solu-tion parameters of the strong afters
作者
宫悦
龙锋
赵敏
杨鹏
王宇玺
梁明剑
乔慧珍
王宇航
Gong Yue;Long Feng;Zhao Min;Yang Peng;Wang Yuxi;Liang Mingjian;Qiao Huizhen;Wang Yuhang(Sichuan Earthquake Agency,Chengdu 610041,China)
出处
《地震学报》
CSCD
北大核心
2024年第2期173-191,共19页
Acta Seismologica Sinica
基金
四川省科技计划项目(2020YJ0475)
国家重点研发计划(2021YFC3000702-05)
2023年度地震预测开放基金(XH23070D)
西藏拉萨地球物理国家野外科学观测站研究课题(NORSLS2104)共同资助.
