The European VLF/LF radio network to search for earthquake precursors: setting up and natural/man-made disturbances

Abstract

Abstract. In the last years disturbances in VLF/LF radio signals related to seismic activity have been presented. The radio data were collected by receivers located on the ground or on satellites. The ground-based research implies systematic data collection by a network of receivers. Since 2000 the "Pacific VLF network", conducted by Japanese researchers, has been in operation. During 2008 a radio receiver was developed by the Italian factory Elettronika (Palo del Colle, Bari). The receiver is equipment working in VLF and LF bands. It can monitor 10 frequencies distributed in these bands and, for each of them, it saves the power level. At the beginning of 2009, five receivers were made for the realization of the "European VLF/LF Network"; two were planned for Italy and one for Greece, Turkey and Romania, respectively. In 2010 the network was enlarged to include a new receiver installed in Portugal. In this work, first the receiver and its setting up in the different places are described. Then, several disturbances in the radio signals related to the transmitters, receivers, meteorological/geomagnetic conditions are presented and described.

Anomalies Observed in VLF and LF Radio Signals on the Occasion of the Western Turkey Earthquake (M<sub>w</sub> = 5.7) on May 19, 2011

“…The European Radio Network and the Turkey Earthquake Figure 1 shows the European VLF/LF Radio Network. The receivers are the Elettronika, the OmniPal and the MSK models described in [19,20]. The first ones can collect, with a sampling rate of 1 min, the intensity of both VLF signals and LF signals (10 in total), the others the intensity and the phase of VLF signals (5 -8 at least) with a sampling rate of 20 s. All data from the various sites are collected on a weekly basis, at the Central Node of the Network located in the Department of Physics of University of Bari (Italy) and are processed for suitable analysis.…”

“…A possible cause [19] could be the meteorological situation in the zone where the transmitter is located. Figure 6 shows the air temperature, the air pressure, the rain and the storms in such zone during April 2011.…”

Precursory Anomaly in VLF/LF Recordings Prior to the Çaglayan (Erzincan-Turkey) Earthquake on July 30th, 2009

“…The network started to operate in March 2009. The data are collected separately by different teams (Biagi et al 2011). The data centre is at the Department of Physics of the University of Bari, which is headquartering of the network.…”

The European VLF/LF radio network: current status

“…Disturbances on the propagation of the VLF/LF radio signals related to these effects have been presented (Kikuchi 1981;Kleimenova et al 2004;Rozhnoi et al 2006a, b). In Biagi et al (2011), it was revealed that the geomagnetic activity affects mainly the VLF radio propagation while the meteorology (conditions in the transmission-reception zones) mainly the LF radio signals. Anyway, if a correlation is claimed between radio disturbances and the meteorological/geomagnetic variations, they must be contemporary.…”