VLF-LF Radio Signals Collected at Bari (South Italy): a Preliminary Analysis on Signal Anomalies Associated with Earthquakes

• Main Authors: BIAGI P. F., PICCOLO R., CASTELLANA L., MAGGIPINTO T., ERMINI A., MARTELLUCCI S., BELLECCI C., MOLCHALOV A., HAYAKAWA M., OHTA K., CAPOZZI, VITO GIACOMO, PERNA, GIUSEPPE
• Other Authors: Biagi, P. F., Piccolo, R., Castellana, L., Maggipinto, T., Ermini, A., Martellucci, S., Bellecci, C., Capozzi, VITO GIACOMO, Perna, Giuseppe, Molchalov, A., Hayakawa, M., Ohta, K.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2004
• Subjects: VLF-LF radio wave anomalie; earthquake precursor; South Italy seismicity; Iceland
• Online Access: http://hdl.handle.net/11369/16125

At the beginning of 2002 an OmniPAL receiver was put into operation at the Department of Physics of Bari University (Southern Italy). The electric field strength of five VLF-LF signals transmitted from United Kingdom (f=16kHz), France (f=20.9kHz), Germany (f=23.4kHz), Iceland (f=37.5 kHz) and Italy (f=54 kHz) has been monitoring with a 5 s sampling frequency. In a first step we reduced the amount of the data taking one datum each 10 min (mean of the 5 min raw data) and then we smoothed these data by a running adjacent averaging over 7 days. Analysing the trends we obtained, we revealed at first in the signal from the Italian transmitter two clear intensity decreases in April 2002 and in August-September 2002. At these times we observed earthquakes with M=4.3 and M=5.6 respectively near the transmitter-receiver path and a precursory effect in the previous decreases appeared. Then, we noted that all of the five radio trends in the time interval March 2002-February 2003 are more disturbed than in other periods; in particular an evident simultaneous decrease appears in January-February 2003. We propose that these disturbances are related to general excitation of the margin between the African and European plates. In a second step we examined the terminator time (evening) changes for the Italian transmitter in July-September 2002, and we found significant deviations from the mean value at the end of August, which is supportive for some precursory ionospheric signature of earthquakes.