2017年棉兰老岛Mw7.0地震前TEC异常分析

Analysis of TEC anomalies before the Mindanao-2017 Mw7.0 earthquake

为缩短传统的震前电离层异常探测方法,如滑动时窗法和滑动四分位法的探测时窗长度,以及弥补异常数据直接删除的不足,文中利用平滑Z分法进行震前TEC值异常分析。采用滑动四分位法、滑动时窗法和平滑Z分法,对2017年菲律宾棉兰老岛地震震前15 d和震后5 d震中附近的4个点做了TEC值异常分析,结果显示3种方法在4个点均检测到震前5~10 d出现明显正异常,检测结果表现出良好的一致性。平滑Z值法相比两种传统动态探测法更加突出异常时段,探测时窗更短。结合震前9 d和7 d的空间异常图像及2017年太阳活动性数据,分析出此次异常由地震引起。

In order to shorten the detection time window length of traditional pre-earthquake ionospheric anomaly detection methods,such as sliding time window method and sliding four minute method,as well as the shortcomings of direct deletion of anomalous data,this paper uses the smooth Z-score method to carry out the anomaly of TEC value before earthquake analysis.The sliding four minute method,sliding time window method and smooth Z-score method are used to analyze the TEC value abnormalities at four points near the epicenter 15 days before and 5 days after the Mindanao earthquake in the Philippines in 2017.The result shows that the three methods detect obvious positive anomalies 5~10 d before the earthquake at four points,and the detection result shows good consistency.Compared with the two traditional dynamic detection methods,the smooth Z-score method is more prominent anomalous period,and the detection time window is shorter.Combining the 9 d and 7 d spatial anomaly images before the earthquake and the solar activity data in 2017,it is founded that the anomaly is caused by the earthquake.