石玉燕4,
丁志峰5,
常利军5,
张玲4,
范小平1
1. 南京工业大学交通运输工程学院, 南京 210009
2. 河北省地震动力学重点实验室, 河北 三河 065201
3. 同济大学海洋地质国家重点实验室, 上海 200092
4. 山东省地震局, 济南 250014
5. 中国地震局地球物理研究所, 北京 100081
基金项目: 国家自然科学基金(42004078,41774061,41874051),河北省地震动力学重点实验室开放基金项目(FZ212205),江苏省高等学校自然科学研究项目(20KJB170006),江苏省"双创计划"和同济大学海洋地质国家重点实验室访问****基金(MGK202012)共同资助
详细信息
作者简介: 郑拓, 男, 1992年生, 讲师, 主要从事地震各向异性方面的研究.E-mail: zhengtuo@njtech.edu.cn
中图分类号: P315 收稿日期:2020-05-29
修回日期:2021-04-23
上线日期:2021-07-10
Variations of local S-wave splitting in the near field of the 2020 Jinan ML4.4 earthquake
ZHENG Tuo1,2,3,,SHI YuYan4,
DING ZhiFeng5,
CHANG LiJun5,
ZHANG Ling4,
FAN XiaoPing1
1. College of Transportation Science and Engineering, Nanjing Tech University, Nanjing 210009, China
2. Hebei Key Laboratory of Earthquake Dynamics, Hebei Sanhe 065201, China
3. State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China
4. Earthquake Administration of Shandong Province, Jinan 250014, China
5. Institute of Geophysics, China Earthquake Administration, Beijing 100081, China
MSC: P315
--> Received Date: 29 May 2020
Revised Date: 23 April 2021
Available Online: 10 July 2021
摘要
摘要:利用山东省地震局布设的流动地震台站和区域台网固定台站记录的2020年济南ML4.4地震序列资料,通过横波窗内的近震S波分裂计算,获取了各台站上地壳各向异性空间分布和时间变化的结果,对上地壳变形特征以及S波分裂参数(快S波偏振方向和慢S波时间延迟)的时空变化现象进行了分析.结果表明,上地壳各向异性在空间分布上存在分区特征,并且表现出随时间的趋势性变化特征.发震断层东侧的台站LJIN和L3704只有一个快S波优势偏振方向NW向,其上地壳各向异性主要受控于断裂结构;发震断层西侧的L3705台,以及震源区外的FEIC和PYI台主要表现为NE向,反映出区域应力场控制的上地壳各向异性;而靠近长清断裂带的L3706和CHQ台,表现出两个近于垂直的快S波偏振方向,反映了不同射线路径上S波分裂的不同特征.震源区内台站的慢S波时间延迟平均值大于震源区外各台站,表明济南ML4.4地震孕育过程中震源区的应力积累水平高于周边地区.震源区内CHQ台的慢S波时间延迟在主震前较低,在主震后迅速增大,一段时间后逐渐减小并趋于恢复到震前水平,反映了济南ML4.4地震发震前的孕育、主震和余震活动的释放及调整过程中,震源区应力场的动态变化对上地壳各向异性影响十分显著.此外,余震密集区台站的慢S波时间延迟高值仍然高于震前水平,暗示余震密集区的应力释放和调整的过程可能仍将持续.
关键词: 地震各向异性/
S波分裂/
上地壳/
应力场/
济南地震
Abstract:Based on the seismic data recorded by 7 broadband stations of the Earthquake Administration of Shandong Province, this study performs the S-wave splitting analysis method to obtain the spatial distribution and temporal changes of seismic anisotropy in the upper crust, where the Jinan ML4.4 earthquake occurred on February 18, 2020. The resulting fast polarization directions have partition characteristics, and the delay times show systematic variations. In terms of the spatial distribution, the stations LJIN and L3704 located on the eastern side of the seismogenic fault show fault parallel fast polarization orientation, meaning the upper crustal anisotropy closely related to the fault structures. The station L3705 located on the western side of the seismogenic fault and stations FEIC and PYI outside the source region, are dominantly NE fast polarization orientation, reflecting the anisotropy in the upper crust controlled by the regional stress field. The stations L3706 and CHQ near the Changqing Fault Zone show two nearly vertical fast polarization orientations, which may reflect the different characteristics of S wave splitting in different ray paths. The average normalized delay times of the stations in the source region are greater than those outside the source region, which indicates that the stress accumulation in the source region is higher than that in the surrounding area during the seismogenic process. In terms of the time domain, the normalized delay times at station CHQ are relatively low before the main earthquake, and increase rapidly after the main earthquake, and gradually decrease after a period of time and tend to return to the pre-earthquake level, which reflects that the the upper crustal anisotropy is significantly affected by the stress release and adjustment caused by the main earthquake and aftershocks. In addition, the high value of the delay times of the stations in the aftershock intensive region is still higher than that before the earthquake, suggesting that the stress release in the aftershock intensive region may last for a period.
Key words:Seismic anisotropy/
S-wave splitting/
Upper crust/
Stress field/
2020 Jinan earthquake
PDF全文下载地址:
http://www.geophy.cn/data/article/export-pdf?id=2ffeced4-da56-43dd-bee6-055073524fe6