地震电离层响应异常时空演化统计特征

Time-spatial statistical characteristics of seismic influence on ionosphere

本文利用DEMETER卫星运行约6.5年总离子浓度数据和期间全球发生Mw 4.8以上地震参数,自动检测距震中1500 km范围内、震前15天出现电离层扰动,统计电离层扰动异常随地震临近在时间、空间上的演化特征以及异常变化幅度随震级变化规律.数据处理过程中通过控制K_p指数以去掉部分因太阳活动引起的电离层扰动.统计结果显示,地震探测率及电离层响应异常幅度随震级增大而增高.大地震能引起强电离层扰动,扰动幅度可超过背景值1倍以上.全球范围,电离层存在变化活跃区,小幅度电离层扰动趋向于背景变化.北半球中低纬度地区是有利的地震电离层响应监测区.地震相关电离层扰动异常出现频次随地震临近而增高,主要出现在震前一周.空间上,扰动有随地震临近向震中运移的趋势.

This paper is related to the use of the ion density recorded by the low altitude satellite DEMETER and the earthquakes with MW≥4.8 occurring around the world during more than 6 years. There is an automatic search for ionospheric perturbations in the complete satellite data set of ion densities within 1500km from the epicentre of an earthquake and 15 days before the event in order to get time-spatial statistical characteristics of seismic influence on ionosphere. The Kp index is taken into account in order to reduce the effect of the geomagnetic activity on the ionosphere. This geomagnetic activity is induced by solar magnetic storms. The results show that the ratio between detected earthquakes and earthquakes to be detected increases with the magnitude of the earthquakes which intuitively makes sense. The large earthquakes are of large average amplitude of the ionospheric influence and some of them are as two times as the background value. Globally, there are some ionospheric active zones, i.e. the South Atlantic Magnetic Anomaly, where small perturbations appear more frequently, and advantage earthquake detection areas, i.e. low-middle latitude of the north-sphere, where the perturbations are with near relationship with the earthquake detected. Most of perturbations appear one week before the events and they move spatially toward the epicentre as the earthquake comes near.