山东乳山震群震源参数变化及其尺度关系  

Scale relationship and variation of source parameters of Rushan earthquake swarm

作　　者：王鹏 郑建常[2] 王宝善[3,4] 王蕊[1] WANG Peng;ZHENG Jian-chang;WANG Bao-shan;WANG Rui(Dongying Earthquake Monitoring Center,Dongying 257091,China;Shandong Earthquake Agency,Jinan 250102,China;Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,China)

机构地区：[1]东营市地震监测中心,东营257091 [2]山东省地震局,济南250102 [3]中国地震局地球物理研究所,北京100081 [4]中国科学技术大学地球和空间科学学院,合肥230026

出　　处：《地球物理学进展》2020年第6期2096-2106,共11页Progress in Geophysics

基　　金：山东省地震局科研基金项目(JJ1704Y);中国地震局地震科技星火计划项目(XH18026Y);山东省自然科学基金(ZR2017QD014);山东省重点研发计划(2016GSF120011)联合资助

摘　　要：山东乳山震群自2013年10月开始活动,持续5年多时间,累计记录到ML≥0.0级的地震事件1.3万余次.乳山位于东部沿海弱震地区,却发生了如此长时间、高频度的地震活动,值得深入研究.为了解震群发生、发展过程中震源区介质性质的变化特征,本文利用山东数字地震台网和乳山小孔径台阵记录的地震波形资料,基于Brune圆盘模型,采用S波频谱方法,反演计算了乳山震群167个ML≥2.0级地震的震源参数.结果显示:乳山震群的震源参数明显偏离了震源的自相似模型,拐角频率、应力降、视应力与地震矩成比例关系,其中拐角频率中值随地震矩增大而减小,应力降和视应力中值随地震矩的增大而增大.乳山震群应力降的变化范围是0.02~4.39 MPa,均值是0.58 MPa,视应力在0.008~1.79 MPa之间,均值是0.23 MPa,应力降和视应力变化范围较大,达到了2个量级以上,均值水平较低.震群中3次ML>4.5级中有2次地震发生前后拐角频率、视应力等震源参数出现了明显的变化,同时震源参数在空间上差异较大,相对高应力值的地震大多位于震群西北端,深度在5 km左右.最后简单讨论了乳山震群震源参数研究结果的物理意义.The Rushan earthquake swarm has been active since October 2013 and lasted for more than five years in shandong province. The frequency of small earthquakes reached more than 13,000 times. Located in the eastern part of the eastern Jiaodong uplift, Rushan belongs to the Dabieshan-Sulu superhigh pressure collision orogen, which is affected by the subduction of the ancient Pacific plate and the sinistral translation of the TanLu fault. Rushan is located in the weak earthquake area in the east coast of China. It is a rare small earthquake swarm with such a long duration in the weak earthquake area of the eastern China. By studying the spatial and temporal variation characteristics of various seismic source parameters, we can understand stress background of earthquake preparation and occurrence, as well as the kinematic and dynamic characteristics of faults.In order to further study the mechanism of seismic swarm activity and seismic structure, a small aperture array composed of 18 mobile platforms was set up in Rushan area in May 2014, we accumulated abundant observation data. In this paper, by the digital seismic network of shandong and Rushan small aperture array records of seismic waveform data, we use the S wave spectrum method based on the Brune source model by genetic algorithm, and inversion Rushan swarm a group of 167 M_L≥2.0 earthquake source parameters, such as corner frequency, stress drop and apparent stress, then analyzing on the occurrence and development of dielectric properties of the source area in Rushan swarm. The results show that the corner frequency is negatively correlated with the magnitude of earthquake and decreases with magnitude. Before the three 4.5 magnitude earthquakes in Rushan earthquake swarm, the corner frequency showed a relatively low value, and there was a process of increasing the corner frequency, which may be related to the degree of medium fragmentation in the source area. The apparent stress is positively correlated with magnitude and increases with magnitude. The two even

关 键 词：乳山震群 震源参数 拐角频率 视应力 应力降 尺度关系 

分 类 号：P315[天文地球—地震学]