57 research outputs found
A possible radio anomaly observed on the occasion of the MW=6.0 earthquake occurred in Dodecanese islands at the end of January 2020
No full textSince 2009, several VLF/LF radio receivers have been installed throughout Europe in order to realize a European radio network for studying the radio precursors of earthquakes, called the INFREP network. The current network has nine VLF/LF receiving stations, two in Romania and Greece, one in Italy, Austria, Portugal, Cyprus, and Serbia. The receivers can measure with 1 min sampling rate the intensity of 10 radio signals in the band VLF (10-50 kHz) and LF (150-300 kHz). The scope of existing transmitters is manifold, e.g. they are used for radio broadcast (LF), for radio- navigation or time signals and mainly for military purposes in the VLF range. At the end of January 2020 an intense seismic crisis occurred in Dodecanese Islands; the main event (Mw= 6.0) occurred on January 30. This seismic activity occurred in the "sensitive" area of the INFREP network. The analysis of the data collected by INFREP receivers has revealed clear anomalies in three VLF signals appearing some days before the main earthquake. The anomalies appear in the trends collected by the Cyprus receiver and the epicenter is inside the 5th Fresnel ellipses defined by transmitters- receiver. Here we report the data analysis and we present in detail the anomalies. The possibility that they are precursors of the quoted earthquake seems significant.
Biagi, P.F., Colella, R., Schiavulli, L., Ermini, A., Boudjada, M., Eichelberger, H., Schwingenschuh, K., Katzis, K., Contadakis, M.E., Skeberis, C., Moldovan, I.A. and Bezzeghoud, M. (2019) The INFREP Network: Present Situation and Recent Results. Open Journal of Earthquake Research,8, 101-115. https://doi.org/10.4236/ojer.2019.8200
EARTHQUAKE PRECURSOR RESEARCH: GROUND-SATELLITE OBSERVATIONS, LABORATORY EXPERIMENTS, AND THEORETICAL MODELS PREFACE
No full textAnalysis of the LF data collected by the European radio network during one year
No full textDuring 2008 a radio receiver was developed by the Italian factory Elettronika. The receiver is an equipment working in VLF (15-60 kHz) and LF (150-300 kHz) bands. It can monitor 10 frequencies distributed in these bands and,
for each of them, saves the electric field intensity. During 2009 six receivers were installed for the realization of
the “European VLF/LF network”. Actually, two of them are into operation in Italy and one in Greece, Turkey, Portugal and Romania, respectively; a sampling rate of 1 minute is used. The LF radio data collected from July 2009
to December 2010 have been analysed. At first, for each radio signal, the day time data and the night time ones
were separated. Taking into account that the LF signals are characterized by the ground wave and the sky wave
propagation modes, the day data are related to the ground wave and the night data to the sky wave. In a first analysis
the effect of the solar activity and of the thunderstorm activity was pointed out in the different trends. Then the
wavelet analysis was applied on the same trends. Some anomalies probably related to earthquakes occurred nearby
some transmitter-receiver path with M>5 were revealed
Application of differential analysis of VLF signals for seismic-ionospheric precursor detection from multiple receivers
No full text
Wavelet analysis of the LF radio signals collected by the European VLF/LF network from July 2009 to April 2011
No full text<p>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.</p><p> </p>
Present status and preliminary results of the VLF/LF radio recording European network installed in 2009.
No full textIn January 2009 a European network of receivers able to measure the electric field intensity from various VLF/LF
broadcasting stations located throughout Europe, was installed. Five new receivers constructed by an Italian
enterprise have been delivered to Greece, Romania, Turkey and to the Italian team. The motivation of this effort
is to study the possible connections between the preparatory phase of earthquakes and perturbations in the
transmitted radio signals.
The receivers can be reached via ftp and gsm mobile connection, thus allowing a real time data collection. We
present here the status of the network and the various testing steps performed in order to achieve a correct set up.
We show how antennas variations, receivers locations and changes of selected frequencies affect the performances
of the whole network.
After this necessary testing period, several LF/VLF radio signals are now simultaneously and continuously being
sampled by the five receivers.
As a preliminary result we inspect also specific cases in which an anomaly in the radio signals is clearly related to
the transmitter or to the receiver (e.g. meteorological conditions around the sampling site). At a basic level, the
analysis adopted consists in a simple statistical evaluation of the signals by comparing the instantaneous values to
the trend of the signal
The European Network for studying the radio precursors of earthquakes: Principal Component Analysis of LF radio signals collected during July 2009 - April 2011
No full textSince 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
Pre-seismic radio anomalies observed on the occasion of the Mw= 6.7 and Mw = 5.0 earthquakes occurred offshore near the southwest coast of Turkey on July-August, 2017
No full textThe INFREP radio network has been operational in Europe since 2009, in order to reveal possible radio precursors
of earthquakes. Currently the network is consisted of ten receivers. There are two receivers located in Italy, two in
Romania and two in Greece whereas Austria, Portugal, Cyprus and Georgia have one each. The receivers, realized
by an Italian factory, can measure the intensity of 10 radio signals in the VLF (10-50 kHz) and LF (150-300
kHz) bands. On July 20, 2017 a strong (Mw=6.7) earthquake occurred offshore, near the coast of Turkey and
Kos island (Greece); on August 8 an earthquake with Mw=5.0 occurred practically in the same zone. The focal
depth was 10 km for both the events. The epicentres are inside the “sensitive” area of the INFREP network. On
both the occasions, evident pre-seismic disturbances were pointed out in the DHO (23.4 kHz) signal collected by
the Cyprus receiver. On November 7, an earthquake with Mw =5.1 occurred offshore at about 120 km from the
previous ones, on south-east direction. Also in this case an anomaly was observed on the quoted signal. The focal
depth of the earthquake was 70 km, large enough to produce detectable anomalies; in addition a more evident
anomaly appeared on the DHO radio signal collected by the Crete receiver, the sensitive Fresnel zone of which is
out the epicentre area of the earthquake. These circumstances suggest a possible cause of the anomalies different
from the seismicity and indeed a disturbed meteorological situation pointed out. All the anomalies we present,
were revealed by the on-line warning system based on the Wavelet analysis, planned and realized in the frame of
the INFREP cooperation
Anomalies observed in VLF and LF Radio Signals on the occasion of the western Turkey Earthquake (M=5.7) on may 19, 2011
No full textSince 2009 a network of VLF (20 - 60 kHz) and LF (150 - 300 kHz) radio receivers is operating 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, of which three are located in Italy and one is in Austria, Greece, Portugal, Romania, Russia and Turkey. On May 19, 2001 an earthquake (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 the Wavelet spectra, the Principal Component Analysis and the Standard Deviation trends as different methods of analysis. Evident anomalies were revealed both in the signals broadcasted by the TRT transmitter (180 kHz) located near Ankara and in a VLF signal coming from a transmitter located in Western Europe and collected by the receiver TUR of the network located in eastern Turkey. Evident precursor phases were pointed out. Some differences in the efficiency of the three analysis methods were revealed
- …
