A qualitative study of the seismo-ionospheric precursors prior to the 6 April 2009 earthquake in L'Aquila, Italy

Abstract

Abstract. In this paper we use the Cross Correlation analysis method in conjunction with the Empirical Mode Decomposition to analyze foF2 signals collected from Rome, Athens and San Vito ionospheric stations, in order to verify the existence of seismo-ionospheric precursors prior to M=6.3 L'Aquila earthquake in Italy. The adaptive nature of EMD allows for removing the geophysical noise from the foF2 signals, and then to calculate the correlation coefficient between them. According to the cross correlation coefficient theory, we expect the stations which located inside the earthquake preparation area, as evaluated using Dobrovolsky equation, to capture the ionospheric disturbances generated by the seismic event. On the other hand the stations outside of this area are expected to remain unaffected. The results of our study are in accordance with the theoretical model, evidencing ionospheric modification prior to L'Aquila earthquake in a certain area around the epicenter. However, it was found that the selection of stations at the limits of the theoretically estimated earthquake preparation area is not the best choice when the cross correlation method is applied, since the modification of the ionosphere over these stations may not be enough for the ionospheric precursors to appear. Our experimental results also show that when a seismic event constitutes the main shock after a series of pre-seismic activity, precursors may appear as early as 22 days prior to the event.

Geosphere coupling and hydrothermal anomalies before the 2009 <i>M</i><sub>w</sub> 6.3 L'Aquila earthquake in Italy

“…(b) The main thrusts in Italy, with the black solid line box showing the geographical location of (a) (Benoit et al, 2011). Rozhnoi et al, 2009;Tsolis and Xenos, 2010). Many of the existing reports revealed the existence of temporal quasisynchronism among the several anomalies of different parameters related to different geospheres (Table 1).…”

Effect of tidal triggering on seismicity in Taiwan revealed by the empirical mode decomposition method

“…As a final remark, we emphasize that other methods could be also used to evaluate the tidal effect in various geophysical signals in addition to the EMD-based approach proposed here (Huang and Liu, 2006;Tsolis and Xenos, 2010). One is the BAYTAP method, which has been used to analyze geoelectric potential data (Huang and Liu, 2006).…”

<i>Brief communication</i> "A pre seismic radio anomaly revealed in the area where the Abruzzo earthquake (<i>M</i>=6.3) occurred on 6 April 2009"

“…However, in our opinion the previous occurrence is unlikely, because we consider that: (a) we have sampled in central Italy the RMC signal constantly from 1994, and the broadcasting in the direction of Italy has never been interrupted, (b) the receiver in the Amare cave, where the anomaly in the radio signal was observed, is close (15 km) to the epicentre of the 6 April 2009 L'Aquila earthquake, and in the zone most sensitive to possible radio signal disturbances Molchanov and Hayakawa, 1998), (c) the anomaly appeared exactly at the same time when different pre-seismic effects (Genzano et al, 2009;Papadopoulos et al, 2010;Papanikolaou et al, 2010;Pergola et al, 2010;Tsolis and Xenos, 2010), including decreases of the intensity of other radio signals (Rozhnoi et al, 2009), were observed in the area.…”