Investigation of GIM-TEC disturbances before M\u2009\u2265\u20096.0 inland earthquakes during 2003\u20132017

Fuying Zhu,Yingchun Jiang

doi:10.1038/s41598-020-74995-w

Fuying Zhu, Yingchun Jiang

Open Access

https://doi.org/10.1038/s41598-020-74995-w

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Abstract

With the rapid development of the Global Navigation Satellite System (GNSS) and its wide applications to atmospheric science research, the global ionosphere map (GIM) total electron content (TEC) data are extensively used as a potential tool to detect ionospheric disturbances related to seismic activity and they are frequently used to statistically study the relation between the ionosphere and earthquakes (EQs). Indeed, due to the distribution of ground based GPS receivers is very sparse or absent in large areas of ocean, the GIM-TEC data over oceans are results of interpolation between stations and extrapolation in both space and time, and therefore, they are not suitable for studying the marine EQs. In this paper, based on the GIM-TEC data, a statistical investigation of ionospheric TEC variations of 15 days before and after the 276 M ≥ 6.0 inland EQs is undertaken. After eliminating the interference of geomagnetic activities, the spatial and temporal distributions of the ionospheric TEC disturbances before and after the EQs are investigated and compared. There are no particularly distinct features in the time distribution of the ionospheric TEC disturbances before the inland EQs. However, there are some differences in the spatial distribution, and the biggest difference is precisely in the epicenter area. On the other hand, the occurrence rates of ionospheric TEC disturbances within 5 days before the EQs are overall higher than those after EQs, in addition both of them slightly increase with the earthquake magnitude. These results suggest that the anomalous variations of the GIM-TEC before the EQs might be related to the seismic activities.

Highlights

The Global Navigation Satellite System (GNSS) has been used as a valuable tool to monitor and estimate ionospheric total electron contents (TECs)[1,2,3,4,5]
According to the method described above, to establish the correlation between the global ionosphere map (GIM)-TEC disturbances and the seismic activities, we statistically investigated the occurrence rates of the every ionospheric TEC value 15 days before and after all the 276 inland EQs
In order to seek a possible statistical significance between the TEC disturbances and the seismic activities, we statistically investigated the space–time distributing of pre-seismic and post-seismic changes in GIM-TEC for 276 global M ≥ 6.0 inland EQs during 2003–2017

Summary

Introduction

The Global Navigation Satellite System (GNSS) has been used as a valuable tool to monitor and estimate ionospheric total electron contents (TECs)[1,2,3,4,5]. The GIM-TEC values over oceans are result of interpolation between stations and extrapolation in both space and time, and the formal error of low latitude values reach a maximum of about 10 TECu2, where 1 TECu = 1016 el/ m2 They are not suitable to study the marine EQs, that is to say, the foregoing statistical studies about the ionospheric TEC disturbances before the EQs (mainly marine EQs) are strictly unreliable. In marine regions there are few GNSS receivers, and as a consequence, most part of the provided information by the TEC global map is based on interpolation, it is not suitable to study the marine EQs. In order to hunting the correlation between the ionospheric TEC disturbances and the seismic activities, we only select the M ≥ 6.0 shallow depths (≤ 60 km) inland EQs around the world from 2003 to 2017 in this study, the EQs data are retrieved from the EQ catalogue of United States Geological Survey (USGS) through the following address (https://earthquake.usgs.gov/earthquakes).

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