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基于平滑伪魏格纳-维勒分布的时频分析方法的震例回溯性研究
廖晓峰, 何畅, 祁玉萍, 李雪浩, 周亚东
四川省地震局, 成都 610041
摘要:
以四川及其邻区现有地磁台站数据为研究对象,基于平滑伪魏格纳-维勒分布的时频分析方法(SPWVD),对其进行时频计算,并对康定地震、九寨沟地震附近地磁台站及中强震活跃时段与平静时段的川滇地区部分地磁台站Z分量滤波后周期为4.4h的振幅变化特征进行回溯性震例分析。研究发现:2014年康定地震之前,震中附近7个地磁台站4.4h振幅存在同步高值异常现象,其中5个台的幅值为震前所研究时段的最高值;九寨沟地震前,震中附近6个台站存在同步相对高值的异常现象,其中3个台的幅值为震前所研究时段的最高值;2014年川滇地震活跃时期,该区域地磁台站普遍存在4.4h振幅同步异常,台站数量多、振幅大,与此时间段内中强地震发生强度呈正相关,在时间上呈现短临特征;2018年川滇地区中强地震活动平静时期,4.4h振幅变化较平稳,异常振幅相对较小,而后活跃期间同步异常的最大振幅增大且异常台站数量增加。综上所述,通过SPWVD时频方法对地磁数据进行处理和分析,以此得到的规律和认识,对未来川滇地区中强地震预测和研判区域地震活动性的强弱有积极意义。
关键词:  地磁Z分量  SPWVD方法  前兆异常  川滇地区  4.4h振幅
DOI:
分类号:P315
基金项目:2019年度四川省地震局科技专项任务(LY1902)、2019年度震情跟踪定向工作任务(2019010415)、2020年度震情跟踪定向工作任务(2020010405)共同资助
Study of Traceable Earthquake Cases Based on Smoothed Pseudo Wigner Ville Time-frequency Analysis
Liao Xiaofeng, He Chang, Qi Yuping, Li Xuehao, Zhou Yadong
Sichuan Earthquake Agency, Chengdu 610041, China
Abstract:
Using the data of available geomagnetic stations in Sichuan and its adjacent areas as the research object,we applied Smooth pseudo-Wigner-Ville(SPWVD)method to calculate the time-frequency. Then we conducted retrospective analysis on the amplitude variation characteristics of geomagnetic stations in Sichuan-Yunnan region during geomagnetic stations near Kangding and Jiuzhaigou earthquakes and active and quiet periods of moderately strong earthquakes with a period of 4.4h after Z component filtering. It is found that before the 2014 kangding earthquake,7 geomagnetic stations near the epicenter had the abnormal phenomenon of synchronous high value in 4.4h amplitude,of which the amplitude of 5 stations was the highest value in the study period before the earthquake. Before the Jiuzhaigou earthquake,six stations near the epicenter had the abnormal phenomenon of relatively high synchronous value,among which the amplitude of three stations was the highest value in the study period. During the active period of Sichuan and Yunnan in 2014,the 4.4h amplitude synchronous anomaly was common in the geomagnetic stations in this region,with the largest number of stations and large amplitude,which is positively related to the occurrence intensity of medium and strong earthquakes in this period,showing short-term and imminent characteristics in time. During the moderate strong seismicity quiet period in Sichuan and Yunnan in 2018,the amplitude variation in 4.4h is relatively stable,and the abnormal amplitude is relatively small,then the maximum amplitude of synchronous anomaly increases and the number of abnormal stations increases during the active period. In summary,SPWVD time-frequency method is capable of processing and analyzing geomagnetic data,and the application of this method will be of significance for the prediction and analysis of regional seismicity of moderate-strong earthquakes in Sichuan-Yunnan region in the future.
Key words:  Geomagnetic Z component  SPWVD method  Precursor anomaly  Sichuan-Yunnan region  Period of 4.4h