Wavelet analysis of the LF radio signals collected by the European VLF/LF network from July 2009 to April 2011

In 2008, a radio receiver that works in very low frequency (VLF; 20-60 kHz) and LF (150-300 kHz) bands was developed by an Italian factory. The receiver can monitor 10 frequencies distributed in these bands, with the measurement for each of them of the electric field intensity. Since 2009, to date, six of these radio receivers have been installed throughout Europe to establish a ‘European VLF/LF Network’. At present, two of these are into operation in Italy, and the remaining four are located in Greece, Turkey, Portugal and Romania. For the present study, the LF radio data collected over about two years were analysed. At first, the day-time data and the night-time data were separated for each radio signal. Taking into account that the LF signals are characterized by ground-wave and sky-wave propagation modes, the day-time data are related to the ground wave and the night-time data to the sky wave. In this framework, the effects of solar activity and storm activity were defined in the different trends. Then, the earthquakes with M ≥5.0 that occurred over the same period were selected, as those located in a 300-km radius around each receiver/transmitter and within the 5th Fresnel zone related to each transmitter-receiver path. Where possible, the wavelet analysis was applied on the time series of the radio signal intensity, and some anomalies related to previous earthquakes were revealed. Except for some doubt in one case, success appears to have been obtained in all of the cases related to the 300 km circles in for the ground waves and the sky waves. For the Fresnel cases, success in two cases and one failure were seen in analysing the sky waves. The failure occurred in August/September, and might be related to the disturbed conditions of the ionosphere in summer

Anomalies Observed in VLF and LF Radio Signals on the Occasion of the Western Turkey Earthquake (Mw = 5.7) on May 19, 2011

VLF radio signals lie in the 10 - 60 kHz frequency band. These radio signals are used for worldwide navigation support, time signals and for military purposes. They are propagated in the earth-ionosphere wave-guide mode along great circle propagation paths. So, their propaga-tion is strongly affected by the ionosphere conditions. LF signals lie in 150 - 300 kHz frequency band. They are used for long way broadcasting by the few (this type of broadcasting is going into disuse) transmitters located in the world. These radio signals are characterized by the ground wave and the sky wave propagation modes [1]. The first generates a stable signal that propagates in the channel Earth-troposphere and is affected by the surface ground and troposphere condition. The second instead gives rise to a signal which varies greatly between day and night, and between summer and winter, and which propagates using the lower ionosphere as a reflector; its propagation is mainly affected by the ionosphere condi-tion, particularly in the zone located in the middle of the transmitter-receiver path. The propagation of the VLF/LF radio signals is affected by different factors such as the meteorological condition, the solar bursts and the geo-magnetic activity. At the same time, variations of some parameters in the ground, in the atmosphere and in the ionosphere occurring during the preparatory phase of earthquakes can produce disturbances in the above men-tioned signals. As already reported by many previous studies [2-18] the disturbances are classified as anoma-lies and different methods of analysis as the residual dA/ dP [15], the terminator time TT [9], the Wavelet spectra and the Principal Component Analysis have been used [6,7]. Here the analysis carried out on LF and VLF radio signals using three different methods on the occasion of a strong earthquake occurred recently in Turkey is pre-sented

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

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

A pre seismic radio anomaly revealed in the area where the Abruzzo earthquake ( M =6.3) occurred on 6 April 2009

Abstract. On 6 April 2009 a strong (Mw=6.3) earthquake occurred in the Abruzzo region (central Italy). Since 1996, the intensity of CLT (f=189 kHz, Sicily, Italy), MCO (f=216 kHz, France) and CZE (f=270 kHz, Czech Republic) broadcast signals has been collected with a ten minutes sampling rate by a receiver operating in a place located about 13 km far from the epicenter. During March 2009, the old receiver was substituted with a new one able to measure, with one minute sampling rate, the intensity of five VLF signals and five LF signals radiated by transmitters located in different zones of Europe. The MCO and CZE transmitters mentioned above are included among them. From 31 March to 1 April the intensity of the MCO radio signal dropped and this drop was observed only in this signal. The possibility that the drop was connected to problems in the transmitter or in the receiver was investigated and excluded. So, the drop indicates a defocusing of the radiated signal. Since no particular meteorological situation along the path transmitter-receiver happened, the defocusing must be related to other causes, and a possibility is presented that it is a precursor of the Abruzzo earthquake

The European Network for studying the radio precursors of earthquakes: Principal Component Analysis of LF radio signals collected during July 2009 - April 2011

Since 2009 a network of VLF (20-60 kHz) and LF (150-300 kHz) radio receivers was put into operation in Europe in order to study the disturbances produced by the earthquakes on the propagation of these signals. In 2011 the network for LF signals was formed by six receivers located two in Italy and one in Greece, Portugal, Romania, and Turkey. The LF radio data collected during about two years have been analysed. Each radio signal has been split in day-time and night-time data; then, the earthquakes with M 5.0, occurred in the same period, located in a 300 km radius around each receiver/transmitter and within the 5th Fresnel zone related to each transmitter-receiver path, have been selected. In this study we adopt the Principal Component Analysis (PCA) to study the radio signal anomalies possibly related to earthquake activity. A detailed comparison with similar studies that use wavelet analysis is done and advantages or drawback of the two methods are pointed out

The European Network for studying the radio precursors of earthquakes: the case of the May 19, 2011 Turkey earthquake (Mw=5.7)

Since 2009 a network of VLF (20-60 kHz) and LF (150-300 kHz) radio receivers was put into operation in Europe in order to study the disturbances produced by the earthquakes on the propagation of these signals. In 2011 the network was formed by nine receivers located three in Italy and one in Austria, Greece, Portugal, Romania, Russia and Turkey. On May 19, 2001 an earthquake with Mw=5.7 occurred in western Turkey, that is inside the “sensitive” area of the network. The radio data collected during April-May 2011 were studied using three different methods of analysis which are the wavelet spectra, the principal component technique and the standard deviation trends. Clear anomalies were revealed both in the signals broadcasted by the TRT transmitter (180 kHz) located near Ankara and in some VLF signals coming from transmitters located in western Europe and collected by the receiver TUR of the network located in eastern Turkey. Evident precursors phases were pointed out. Some difference in the efficiency of the methods of analysis were revealed

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

On 6 April 2009 a strong (Mw=6.3) earthquake occurred in the Abruzzo region (central Italy). Since 1996, the intensity of CLT (f=189 kHz, Sicily, Italy), MCO (f=216 kHz, France) and CZE (f=270 kHz, Czech Republic) broadcast signals has been collected with a ten minutes sampling rate by a receiver operating in a place located about 13 km far from the epicenter. During March 2009, the old receiver was substituted with a new one able to measure, with one minute sampling rate, the intensity of five VLF signals and five LF signals radiated by transmitters located in different zones of Europe. The MCO and CZE transmitters mentioned above are included among them. From 31 March to 1 April the intensity of the MCO radio signal dropped and this drop was observed only in this signal. The possibility that the drop was connected to problems in the transmitter or in the receiver was investigated and excluded. So, the drop indicates a defocusing of the radiated signal. Since no particular meteorological situation along the path transmitter-receiver happened, the defocusing must be related to other causes, and a possibility is presented that it is a precursor of the Abruzzo earthquake

Nanodiamond photocathodes for MPGD-based single photon detectors at future EIC

We are developing gaseous photon detectors for Cherenkov imaging applications in the experiments at the future Electron Ion Collider. CsI, converting photons in the far ultraviolet range, is, so far, the only photoconverter compatible with the operation of gaseous detectors. It is very delicate to handle due to its hygroscopic nature: the absorbed water vapour decomposes the CsI molecule. In addition, its quantum efficiency degrades under ion bombardment. These are the key reasons to quest for novel, less delicate materials for photocathodes adequate for gaseous photon detectors. Layers of hydrogenated nanodiamond particles have recently been proposed as an alternative material and have shown promising characteristics. The performance of nanodiamond photocathodes coupled to thick GEM-based detectors is the object of our ongoing R\&D. The first phase of these studies includes the characterization of thick GEM coated with nanodiamond layers and the robustness of its photoconverting properties with respect to the bombardment by ions from the multiplication process in the gaseous detector. The approach is described in detail as well as all the results obtained so far within these exploratory studies