Ionospheric Disturbances Associated with Earthquake Precursors Investigated by GNSS

Abstract:

Prediction of natural disasters in general and earthquakes, in particular, is becoming increasingly critical in providing early warnings and mitigating catastrophes' effects. Recently, many studies reveal the earthquake relation with ionospheric disturbances. This study investigates global earthquakes with the magnitude (M­_w) from 4.0 ­­to 9.0 in the period from 2006 to February 2020. We use data of 54 permanent GNSS (Global Navigation Satellite Systems) stations to determine total electron content (TEC) values. The selected data ensure strict conditions such as accuracy, the distance from the GNSS stations to the epicentre, and the depth of hypocentre. Probability theory and statistics are also applied to filter the TEC values and to remove gross errors. Based on TEC disturbances, we analyze the impact of the earthquake-related seismic waves on the ionosphere. These ionospheric disturbances are studied in three cases: from two to twelve hours before the mainshocks, three days (before, during, and after) the earthquakes, and one month preceding to earthquakes. The results indicate that TEC fluctuations at the regions occurring earthquakes with magnitudes greater than 6.0 M_w are significant. The amplitude of TEC variations can reach up to ~35 TECU, exceed the level of background fluctuations. These TEC anomalies appear from a few weeks to around 30 minutes before the mainshocks, and the oscillations remain from five to eight minutes. The findings of the research open up a promising possibility for applying global TEC models combined with machine learning techniques to study TEC anomalies associated with earthquake precursors, thereby suggesting near-real-time warnings of earthquakes.