21 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
A multiple receiver - multiple transmitter VLF high-order differential analysis evaluation network for near real-time detection and discrimination of seismic-ionospheric precursor phenomena
No full textApplication of differential analysis of VLF signals for seismic-ionospheric precursor detection from multiple receivers
No full textOptimal Wideband LPDA Design for Efficient Multimedia Content Delivery over Emerging Mobile Computing Systems
No full textAn optimal synthesis of a wideband Log-Periodic
Dipole Array (LPDA) is introduced in the present study. The LPDA optimization is performed under several requirements concerning the standing wave ratio, the forward gain, the gain flatness, the front-to-back ratio and the side lobe level, over a
wide frequency range. The LPDA geometry that complies with the above requirements is suitable for efficient multimedia content delivery. The optimization process is accomplished by applying a recently introduced method called Invasive Weed Optimization (IWO). The method has already been compared to other evolutionary methods and has shown superiority in solving complex non-linear problems in telecommunications and electromagnetics. In the present study, the IWO method has been chosen to optimize an LPDA for operation in the frequency range
800-3300 MHz. Due to its excellent performance, the LPDA can effectively be used for multimedia content reception over future mobile computing systems
Evaluation of disturbances detected on a VLF/LF receiver inside the preparation zone of a sequence of earthquakes.
No full textPre-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
The INFREP Network: Present Situation and Recent Results
No full textVLF/LF (20 - 300 kHz) radio waves propagation is affected by different factors such as meteorological conditions, solar bursts and geomagnetic 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 propagation of the previous signals along their radio paths: these disturbances are the radio precursors.
Since 2009, several VLF/LF radio receivers have been installed throughout Europe in order to realize a European (VLF/LF) radio network for studying
the VLF/LF radio precursors of earthquakes, called the INFREP network. In this paper, at first the description of the present situation of the INFREP
network is presented, that is: the location of the receivers, the location of the VLF/LF transmitters whose signal is sampled, the daily download of the data
collected by the receivers on the INFREP server and the method of data analysis used in order to individuate possible radio precursors. Then the results
obtained on the occasion of recent (2016-2017) seismic activities which occurred in the “sensitive” zone of the INFREP network are presented. The first
case examined is the October 30, 2016 earthquake with Mw = 6.5, which occurred in Central Italy, near Norcia small town; this earthquake was preceded
by a strong shock (Mw = 5.9) which occurred 4 days before. The second case presented is the strong (Mw = 6.7) offshore earthquake which occurred on July
20, 2017, near the coast of Turkey and Kos island (Greece) and the third case is the August 8, 2017 earthquake with Mw = 5.0, which also occurred near
the coast of Turkey and Kos island (Greece). In all the previous cases radio anomalies were revealed in some radio signals collected by the receiver located in Cyprus. The influence of causes different from seismicity as geomagnetic activity and solar burst, meteorological conditions, malfunction of
the receiver and/or the transmitters has been examined and none convincing connections appeared. So, the possibility that the previous anomalies are radio
precursors of the earthquakes seems realistic. Finally, some discrepancy of some of these anomalies with respect to the general peculiarities of the radio
precursors is presented and discussed
Study of VLF/LF wave propagations above seismic areas
No full textAbstract: We report on radio transmitter signals recorded in Europe by INFREP network which is mainly devoted to search for earthquakes electromagnetic precursors (Biagi et al., 2011). We consider in this analysis the detection of transmitter signals recorded by INFREP receivers located in different regions of Europe, i.e. Romania, Italy, Greece and Austria. The aim is the investigation of the electromagnetic environment above earthquakes regions. We selected seismic events which occurred in the year 2016 and characterized by a moment magnitude (Mw) above 5.0 and a depth of less than 50 km. A common method is applied to all events and which involves the analysis of the VLF/LF signal detection taking into consideration the following parameters: (a) the distance transmitters-receivers, (b) the signal to noise ratio during the diurnal and night observations, (c) the daily and night averaged amplitude and (d) the sunset and sunrise termination times. This leads us to specify the key factors which can be considered as criteria to distinguish and to identify earthquakes precursors. We discuss in this contribution the radio wave propagation in the D- and E-layers and their impacts on the VLF/LF amplitude signal. We show that the 'seismic anomaly' requests a more precise analysis of the 'quiet' and 'disturbed' ionospheric conditions and their corresponding spectral traces on the VLF/LF transmitter signals
Possible pre-seismic radio anomalies observed on the occasion of the MW=5.9 and MW=6.5 earthquakes occurred in Central Italy at the end of October 2016
No full textOn October 26, 2016 an earthquake with Mw=5.9 occurred in Central Italy, near Castelsantangelo village; after 4
days the main shock with Mw=6.5 occurred near Norcia small town. The two epicenters are 12 km far from each
other and are located in the sensitive area of the European VLF/LF Radio Network (INFREP). Unfortunately, at the
time of the earthquake, several receivers were out of service, so only the data from Cyprus receiver are available.
Some days before the first earthquake two clear anomalies appeared one after the other in two of the ten signals,
the intensity of which is collected with 1 min sampling rate by this receiver. The two signals are radiated by DHO
transmitter (23.4 kHz) ) located in Rhauderfehn (Germany) and by ICV transmitter (20.27kHz) located in Sardinia
(Italy). The 5th Fresnel zones of the radio paths brush the border of the Dobrovolsky area of the previous main
shock. The anomalies seem to move in the same direction of the two epicenters. Here we present in detail the
anomalies and we discuss the possibility that they are precursors of the quoted earthquakes. As mentioned before,
we have no more data to examine in order to confirm and endorse these anomalies
Wavelet analysis applied on temporal data sets in order to reveal possible pre-seismic radio anomalies and comparison with the trend of the raw data
No full textSince 2009, several radio receivers have been installed throughout Europe in order to realize the INFREP European radio network for studying the VLF (10-50 kHz) and LF (150-300 kHz) radio precursors of earthquakes. Precursors can be related to “anomalies” in the night-time behavior of VLF signals. A suitable method of analysis is the use of the Wavelet spectra. Using the “Morlet function”, the Wavelet transform of a time signal is a complex series that can be usefully represented by its square amplitude, i.e. considering the so-called Wavelet power spectrum.
The power spectrum is a 2D diagram that, once properly normalized with respect to the power of the white noise, gives information on the strength and precise time of occurrence of the various Fourier components, which are present in the original time series. The main difference between the Wavelet power spectra and the Fourier power spectra for the time series is that the former identifies the frequency content along the operational time, which cannot be done with the latter. Anomalies are identified as regions of the Wavelet spectrogram characterized by a sudden increase in the power strength.
On January 30, 2020 an earthquake with Mw= 6.0 occurred in Dodecanese Islands. The results of the Wavelet analysis carried out on data collected some INFREP receivers is compared with the trends of the raw data. The time series from January 24, 2020 till January 31, 2000 was analyzed. The Wavelet spectrogram shows a peak corresponding to a period of 1 day on the days before January 30. This anomaly was found for signals transmitted at the frequencies 19,58 kHz, 20, 27 kHz, 23,40 kHz with an energy in the peak increasing from 19,58 kHz to 23,40 kHz. In particular, the signal at the frequency 19,58 kHz, shows a peak on January 29, while the frequencies 20,27 kHz and 23,40 kHz are characterized by a peak starting on January 28 and continuing to January 29. The results presented in this work shows the perspective use of the Wavelet spectrum analysis as an operational tool for the detection of anomalies in VLF and LF signal potentially related to EQ precursors
