Analysis of the Ionospheric Perturbations Prior to the 2009 L’Aquila and 2002 Molise Earthquakes from Ground- and Space-Based Observations

Abstract

The ionospheric responses to the 2009 L’Aquila (local magnitude ML 5.8 main shock on April 6, 2009) and 2002 San Giuliano di Puglia (ML 5.4 and 5.3, major shocks on October 31, 2002, and November 1, 2002; also known as 2002 Molise earthquakes) seismic sequences, both in central Italy, were investigated in a combined ground satellite study. A multiparametric method based on ionosonde observations of sporadic E and F2 ionospheric layers and an appropriate algorithm for the analysis of the Earth’s magnetic field and electron density satellite measurements were applied to the Rome ionosonde and Challenging Minisatellite Payload satellite data, respectively, looking for middle-term precursory ionospheric anomalies within the preparation zone of the corresponding earthquakes under quiet geomagnetic conditions. Some interesting anomalies were detected prior to the 2009 L’Aquila main shock, including ionosonde anomalies during the same day of the larger foreshock (7 days before the main shock) and the previous day, in coincidence with a magnetic field anomaly by satellite. Less consistent results were obtained for the 2002 Molise seismic sequence, likely due to the lower magnitude of the corresponding events, generating a weak pre-earthquake ionospheric response. In this case, only one variation in the magnetic field measured by satellite 9 days prior to the first major shock met the conditions to be considered anomalous.