2017年九寨沟M7.0地震前临震电离层异常研究

Impending Ionospheric Anomalies before the 2017 Jiuzhaigou M7.0 Earthquake

为研究2017年8月8日四川九寨沟M7.0地震前电离层异常,利用地基GNSS(Global Navigation Satellite System)垂直电子总含量(Vertical Total Electron Content,VTEC)和电离层测高仪F2层临界频率(foF2)观测数据,考察了震前20日内电离层变化,发现震前第4日(8月4日)及地震发生前5小时,震中附近上空出现显著电离层正异常.结合异常对应的日地空间环境分析,认为震前第4日出现的异常由磁暴引起,而发震当日出现的临震电离层异常可能与孕震活动有关.本文表明电离层测高仪具有同GNSS VTEC一致的异常检测结果.相比公布时间滞后的GNSS数据及其产品,测高仪数据的获取更加及时,将两种电离层观测手段结合起来,能实现两种技术优势互补,提高地震电离层监测能力.

In order to investigate the ionospheric anomalies before the Jiuzhaigou M7.0 earthquake which occurred on August 8,2017 in Sichuan,we used ground-based GNSS VTEC and ionosonde foF2 observation data to investigate the ionospheric variations in 20 days before the earthquake.We found that two significant positive ionospheric anomalies appeared near the epicenter 4 days and 5 hours before the earthquake.Considering the solar-terrestrial space environment around the days of the anomalies,we conclude that the former anomaly should be caused by a magnetic storm,whereas the latter occurring on the day of the earthquake may be caused by the seismogenic activity.This paper indicates that the ionosonde measurements are consistent with GNSS VTEC observations on ionospheric anomaly detection.Compared with the lag in the release time of GNSS data and products,ionosonde acquires data more timely.Combining the two ionospheric observation methods will promote superiority complement for each other,and then improve capabilities of seismo-ionospheric monitoring.