The modifications of some atmospheric physical properties prior to a high magnitude earthquake were recently debated in the frame of the Lithosphere-Atmosphere-Ionosphere (LAI) Coupling model. Among this variety of phenomena, the ionization of air at the ionospheric levels due to leaking of gases from earth crust through the analysis of long time series of GNSS (Global Navigation Satellite System) signals was investigated in this work. Several authors used the dispersive properties of the ionospheric strata towards the GNSS signals to detect possible ionospheric anomalies over areas affected by earthquakes and some evidences were encountered. However, the spatial scale and temporal domains over which such a disturbances come into evidence is still a controversial item. Furthermore, the correspondence by chance between ionospheric disturbances and relevant seismic activity is even more difficult to model whenever the reference time period and spatial extent of investigation are confined. Problems could also arise from phenomena due to solar activity (now at culmination within the 11 years-long solar cycle) because such global effects could reduce the ability to detect disturbances at regional or local spatial scale. In this work, a five-years (2008-2012) long series of high resolution ionospheric maps produced from GNSS data collected by a network of tens of GPS permanent stations distributed within an area around the city of L’Aquila (Abruzzi, Italy), where an earthquake (M = 6.3) occurred on April 6, 2009, were investigated. Basically, the proposed methodology is able to perform a time series analysis of the TEC (Total Electron Content) maps and, eventually, define the temporal domain of potential ionospheric disturbances. The separation between local and global effects has been obtained by the comparison of local and global TEC series. This data processing shows several periods where anomalies were detected in the ionospheric activity even though their statistical significance and an the correlation with seismic activity available around the time of the main shock is still controversial.
Ionospheric activity and its possible connection with seismicity: contributes from the analysis of long time series of GNSS signals
DE GIGLIO, MICHAELA;BARBARELLA, MAURIZIO;
2013
Abstract
The modifications of some atmospheric physical properties prior to a high magnitude earthquake were recently debated in the frame of the Lithosphere-Atmosphere-Ionosphere (LAI) Coupling model. Among this variety of phenomena, the ionization of air at the ionospheric levels due to leaking of gases from earth crust through the analysis of long time series of GNSS (Global Navigation Satellite System) signals was investigated in this work. Several authors used the dispersive properties of the ionospheric strata towards the GNSS signals to detect possible ionospheric anomalies over areas affected by earthquakes and some evidences were encountered. However, the spatial scale and temporal domains over which such a disturbances come into evidence is still a controversial item. Furthermore, the correspondence by chance between ionospheric disturbances and relevant seismic activity is even more difficult to model whenever the reference time period and spatial extent of investigation are confined. Problems could also arise from phenomena due to solar activity (now at culmination within the 11 years-long solar cycle) because such global effects could reduce the ability to detect disturbances at regional or local spatial scale. In this work, a five-years (2008-2012) long series of high resolution ionospheric maps produced from GNSS data collected by a network of tens of GPS permanent stations distributed within an area around the city of L’Aquila (Abruzzi, Italy), where an earthquake (M = 6.3) occurred on April 6, 2009, were investigated. Basically, the proposed methodology is able to perform a time series analysis of the TEC (Total Electron Content) maps and, eventually, define the temporal domain of potential ionospheric disturbances. The separation between local and global effects has been obtained by the comparison of local and global TEC series. This data processing shows several periods where anomalies were detected in the ionospheric activity even though their statistical significance and an the correlation with seismic activity available around the time of the main shock is still controversial.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
