Singular spectrum analysis of ionospheric anomalies preceding great earthquakes: Case studies of Kaikoura and Fukushima earthquakes
Singular spectrum analysis of ionospheric anomalies preceding great earthquakes: Case studies of Kaikoura and Fukushima earthquakes
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大地震前电离层异常的奇异谱分析：凯库拉和福岛地震的案例研究
DOI：
10.1016/j.jog.2019.01.005
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发表时间：
2019-02-01
影响因子：
2.3
通讯作者：
Kong, Qiaoli
中科院分区：
文献类型：
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作者：
Guo, Jinyun;Shi, Kunpeng;Kong, Qiaoli
为了研究地震-电离层耦合，引入奇异谱分析（SSA）方法对大震前电离层异常进行检测。采用SSA方法对总电子含量（TEC）序列进行分解，并将分解后的各分量进行w-相关分析，得到TEC主成分。在安静的日地环境期间的背景TEC值被用来计算标准偏差，随后被用来确定背景值的上限和下限。提取国际GNSS服务（IGS）发布的全球电离层图（GIM）在震中附近的均方根误差，并进行平均，得到阈值，用于抑制震前TEC异常检测过程中的系统误差效应。在2016年11月13日新西兰Kaikoura Mw7.8地震和2016年11月21日日本福岛Mw6.9地震发生之前，这种新方法被用于检测电离层异常。利用滑动四分位距（IQR）方法对TEC数据进行了进一步分析，以验证SSA的可靠性和可行性。结果表明，10月25日、28日和11月10日，两个震中上空的TEC异常都很明显。结果表明，与IQR相比，SSA能更好地检测出TEC异常，使由外部因素引起的TEC异常更加明显。利用F10.7、Dst和Kp指数对日地环境进行分析，发现这三天都有磁暴发生。为了确定和提取地震电离层异常的潜在前兆信息，还分析了具有SSA和IQR的TEC异常区域的全球分布。结果表明，SSA探测到的准备区存在明显的地震-电离层耦合效应异常特征。此外，由互小波分析得到的TEC异常与Dst指数的关系表明，IQR探测到的准备区以外的电离层异常是磁暴引起的。与此相反，SSA在这些区域检测到的TEC异常的范围和幅度远小于IQR。总体而言，这些结果表明，SSA可以有效地消除太阳-地磁活动的影响，提取地震-电离层耦合异常。
To study seismo-ionospheric coupling, the singular spectrum analysis (SSA) method was introduced to detect ionospheric anomalies preceding great earthquakes. The SSA method was used to decompose the total electronic content (TEC) series, and the reconstructed components (RCs) were combined to obtain the TEC principal components using w-correlation. The background TEC value during the quiet solar-terrestrial environment period was used to calculate the standard deviation, which was subsequently used to determine the upper and lower bounds of the background values. The root-mean-square error of the global ionosphere map (GIM) published by the International GNSS Service (IGS) near the earthquake epicenter was extracted and averaged to obtain the threshold, which was then used to suppress the systematic error effect during the detection of pre earthquake TEC anomalies process. This new method was used to detect ionospheric anomalies prior to the occurrence of the Mw7.8 Kaikoura earthquake in New Zealand on 13 November 2016 and the Mw6.9 Fukushima earthquake in Japan on 21 November 2016. The TEC data were further analysed with the sliding interquartile range (IQR) method to verify the reliability and feasibility of the SSA. The results showed that the TEC anomalies over these two epicenters were clearly detected on 25 and 28 October and 10 November. Our results showed that compared with IQR, SSA could detect TEC anomalies with a larger magnitude, making TEC anomalies caused by external factors more visible. Furthermore, based on the analysis of the solar-terrestrial environment using the data of F10.7, Dst and Kp indices, it is found that magnetic storms occurred during these three days. To identify and extract potential precursor information on seismo-ionospheric anomalies, the global distribution of TEC anomalous areas with SSA and IQR was also analysed. The results indicated the presence ofobvious anomalous characteristics of the seismic-ionospheric coupling effect in the preparation zones detected by SSA. In addition, the relation between TEC anomaly and Dst index detected by the cross-wavelet analysis indicated that ionospheric anomalies outside the preparation zones detected by IQR were caused by magnetic storms. In contrast, the ranges and amplitudes of TEC anomalies detected by SSA in these zones were much smaller than those with IQR. Overall, these findings demonstrate that SSA can effectively eliminate the effect of solar-geomagnetic activity and extract seismic-ionospheric coupling anomalies.