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Anomalies Observed in VLF and LF Radio Signals on the Occasion of the Western Turkey Earthquake (Mw = 5.7) on May 19, 2011  [PDF]
Pier Francesco Biagi, Flavia Righetti, Tommaso Maggipinto, Luigi Schiavulli, Teresa Ligonzo, Anita Ermini, Iren Adelina Moldovan, Adrian Septimiu Moldovan, Hugo Gon?alves Silva, Mourad Bezzeghoud, Michael E. Contadakis, Dimitrios N. Arabelos, Thomas D. Xenos, Aydin Buyuksarac
International Journal of Geosciences (IJG) , 2012, DOI: 10.4236/ijg.2012.324086
Abstract: Since 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.
On the ionospheric perturbation associated with the 2007 Niigata Chuetsu-oki earthquake, as seen from subionospheric VLF/LF network observations  [PDF]
M. Hayakawa,T. Horie,M. Yoshida,Y. Kasahara
Natural Hazards and Earth System Sciences (NHESS) & Discussions (NHESSD) , 2008,
Abstract: In order to investigate any precursory effect of ionospheric perturbations associated with the large 2007 Niigata Chuetsu-oki earthquake (16 July 2007) (magnitude, 6.8), we have made full use of our VLF/LF network observation in Japan by examing the four propagation paths; JJI transmitter (Kyusyu, Ebino)-MSR (Moshiri, Hokkaido), JJY transmitter (Fukushima)-MSR, JJY-KOC (Kochi) and JJI-CBA (Tateyama, Chiba). For the former two paths of JJI-MSR and JJY-MSR, we have observed significant propagation anomalies (both a decrease in nighttime average amplitude and an enhancement in nighttime amplitude fluctuation both satisfying the 2σ (σ: standard deviation) criteria) on 8–9 July, about one week before the earthquake. However, the lack of observation for the path from JJY-KOC, has enabled us to make no conclusion for this path. On the other hand, the path from JJI-CBA does not seem to be perturbed. Although this earthquake is very big and shallow, the amount of VLF anomaly for this earthquake is not so pronounced as expected, probably because the epicenter is not unfortunately located within the sensitive areas of any propagation paths. These observational facts suggest that the lower ionosphere above the epicenter is perturbed definitely prior to the earthquake, with radius of a few hundred kilometers.
Ionospheric turbulence from ground-based and satellite VLF/LF transmitter signal observations for the Simushir earthquake (November 15, 2006)
Alexander Rozhnoi,Maria Solovieva,Michel Parrot,Masashi Hayakawa
Annals of Geophysics , 2012, DOI: 10.4401/ag-5190
Abstract: Signals from very low frequency (VLF)/ low frequency (LF) transmitters recorded on the ground station at Petropavlovsk-Kamchatsky and on board the French DEMETER satellite were analyzed for the Simushir earthquake (M 8.3; November 15, 2006). The period of analysis was from October 1, 2006, to January 31, 2007. The ground and satellite data were processed by a method based on the difference between the real signal at night-time and the model signal. The model for the ground observations was the monthly averaged signal amplitudes and phases, as calculated for the quiet days of every month. For the satellite data, a two-dimensional model of the signal distribution over the selected area was constructed. Preseismic effects were found several days before the earthquake, in both the ground and satellite observations.
The European VLF/LF radio network to search for earthquake precursors: setting up and natural/man-made disturbances  [PDF]
P. F. Biagi,T. Maggipinto,F. Righetti,D. Loiacono
Natural Hazards and Earth System Sciences (NHESS) & Discussions (NHESSD) , 2011, DOI: 10.5194/nhess-11-333-2011
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.
Possible precursor to the March 11, 2011, Japan earthquake: ionospheric perturbations as seen by subionospheric very low frequency/low frequency propagation
Masashi Hayakawa,Yasuhide Hobara,Yoshihiro Yasuda,Hiroki Yamaguchi
Annals of Geophysics , 2012, DOI: 10.4401/ag-5357
Abstract: This study reports on a possible very low frequency/low frequency (VLF/LF) subionospheric precursor to a recent earthquake in Japan. As the epicenter of this large Japanese earthquake on March 11, 2011, was located just on the great-circle path from one of our VLF/LF network stations (Chofu) to the NLK US transmitter, we examined the propagation characteristics mainly associated with the signals from the NLK transmitter, as observed at three of the stations in Japan (Chofu, Kasugai and Kochi). On March 5 and 6, 2011, a remarkable anomaly was found on the path from NLK to Chofu, which is highly likely to have been a precursor to this earthquake. The anomaly in the night-time average amplitude at Chofu was characterized by a serious decrease in the signal that exceeded 4v (v: standard deviations). The anomaly was found on the same days on the other propagation paths (from NLK to both Kasugai and Kochi), although it was less enhanced. Finally, this propagation anomaly is extensively discussed with respect to the geomagnetic activity, and we also compare this anomaly with the properties related to the former 2004 Sumatra earthquake that had nearly the same magnitude as this March 11, 2011, earthquake.
VLF/LF Radio Sounding of Ionospheric Perturbations Associated with Earthquakes  [PDF]
Masashi Hayakawa
Sensors , 2007, DOI: 10.3390/s7071141
Abstract: It is recently recognized that the ionosphere is very sensitive to seismic effects,and the detection of ionospheric perturbations associated with earthquakes, seems to bevery promising for short-term earthquake prediction. We have proposed a possible use ofVLF/LF (very low frequency (3-30 kHz) /low frequency (30-300 kHz)) radio sounding ofthe seismo-ionospheric perturbations. A brief history of the use of subionospheric VLF/LFpropagation for the short-term earthquake prediction is given, followed by a significantfinding of ionospheric perturbation for the Kobe earthquake in 1995. After showingprevious VLF/LF results, we present the latest VLF/LF findings; One is the statisticalcorrelation of the ionospheric perturbation with earthquakes and the second is a case studyfor the Sumatra earthquake in December, 2004, indicating the spatical scale and dynamicsof ionospheric perturbation for this earthquake.
Large Earthquake Prediction Methods  [PDF]
Manana Kachakhidze, Nino Kachakhidze-Murphy, Badri Khvitia, Giorgi Ramishvili
Open Journal of Earthquake Research (OJER) , 2019, DOI: 10.4236/ojer.2019.84014
Abstract: At the present time rather diverse and interesting papers are published on the basis of ground-based and satellite data of earth VLF/LF and ULF electromagnetic (EM) emissions observed during earthquake preparation period. These phenomena are detectable both at laboratory and geological scale. Today in some seismic active countries of the world the network for collecting VLF/LF electromagnetic emissions generated during the process of the earthquake preparation has been organized. Permanent monitoring of frequency spectrum of earth VLF/LF electromagnetic emissions might turn out very useful with the view of prediction of large M ≥ 5 inland earthquakes. To prove the prediction capabilities of earth electromagnetic emissions authors have used avalanche-like unstable model of fault formation and an analogous model of electromagnetic contour, synthesis of which, is rather harmonious. According to the opinion of the authors EM emissions observed during earthquake preparation period are more universal and reliable than other earthquake indicators. In the presented paper, the possible methods of the large earthquake prediction are offered on the base of the European Network of Electromagnetic Radiation (INFREP) data existent before Crete earthquake with M = 5.6 (25/05/2016, 08:36:13 UTC) earthquake. Offered methods are capable of simultaneous determination of all three parameters necessary for incoming M ≥ 5 inland large earthquake prediction (magnitude, epicenter and time of occurring) with certain accuracy.
Further study on the role of atmospheric gravity waves on the seismo-ionospheric perturbations as detected by subionospheric VLF/LF propagation  [PDF]
F. Muto,Y. Kasahara,Y. Hobara,M. Hayakawa
Natural Hazards and Earth System Sciences (NHESS) & Discussions (NHESSD) , 2009,
Abstract: As the target earthquake we have taken a huge earthquake (EQ) named Miyagi-oki earthquake on 16 August 2005 (with magnitude of 7.2) and we have analyzed the 4 month period including the date of this EQ. In addition to our previous analysis on the nighttime average amplitude (trend) and nighttime fluctuation, we have proposed the use of fluctuation power spectra in the frequency rage of atmospheric gravity waves (period=10 min to 100 min) as a third parameter of subionospheric VLF/LF propagation characteristics. Then it is found that this third parameter would be of additional importance in confirming the presence of seismo-ionospheric perturbations. Finally, we have discovered an important role of lunar tidal effect in the VLF/LF data, which appears one and two months before this large EQ.
Disturbances in a VLF radio signal prior the M=4.7 offshore Anzio (central Italy) earthquake on 22 August 2005
P. F. Biagi, L. Castellana, T. Maggipinto, D. Loiacono, V. Augelli, L. Schiavulli, A. Ermini, V. Capozzi, M. S. Solovieva, A. A. Rozhnoi, O. A. Molchanov,M. Hayakawa
Natural Hazards and Earth System Sciences (NHESS) & Discussions (NHESSD) , 2008,
Abstract: On 22 August 2005 an earthquake with magnitude M=4.7 occurred in the Anzio (central Italy) offshore area. From 2002, a VLF-LF radio receiver is into operation in Bari (southern Italy). The intensity and the phase of the signals transmitted by GB (f=16 kHz, United Kingdom), FR (f=20.9 kHz, France), GE (f=23.4 kHz, Germany), IC (f=37.5 kHz, Island) and IT (f=54 kHz, Sicily, Italy) has been monitored with a 5 s sampling rate. The previous epicenter is near enough to some of the radio paths and the data collected were studied in order to reveal possible seismic effects. The raw analysis revealed a clear drop in the intensity of the FR radio signal on 19 August. Then the wavelet analysis was applied to the intensity and the phase data of the different radio signals. In the mentioned day an increase in the band 60–120 min was revealed in the spectra of the FR signal. Then the principal component analysis was applied and again the 19 August stood up as an anomalous day for the FR radio signal. The path of this signal, among the paths of the five radio signals collected by the Bari receiver, is the nearest to the mentioned epicentre and the anomaly revealed on 19 August appears as a precursor of the earthquake. This result confirms the possible precursor revealed by other researchers in the air Rn content in a site located 5 miles far from the epicenter.
VLF/LF Amplitude Perturbations before Tuscany Earthquakes, 2013  [PDF]
Balaram Khadka, Keshav Prasad Kandel, Sudikshya Pant, Karan Bhatta, Basu Dev Ghimire
Natural Science (NS) , 2017, DOI: 10.4236/ns.2017.912041
Abstract: The US Navy VLF/LF Transmitter’s NSY signal (45.9 kHz) transmitted from Niscemi, Sicily, Italy, and received at the Kiel Long Wave Monitor, Germany, was analyzed for the period of two months, May and June (EQ-month) of 2013. There were 12 earthquakes of magnitude greater than 4 that hit Italy in these two months,?of which the earthquake of 21st June having magnitude of 5.2?and a shallow focal depth of 5 km was the major one. We studied the earthquake of 21st of June 2013, which struck Tuscany,?Central Italy, (44.1713°N and?10.2082°E) at 10:33 UT, and also analyzed the effects of this earthquake on the?sub-ionos-?pheric VLF/LF signals. In addition, we also studied another earthquake, of magnitude 4.9, which hit the same place at 14:40 UT on 30th of June and had shallow focal depth of 10 km. We assessed the data using terminator time (TT) method and night time fluctuation method and found unusual changes in VLF/LF amplitudes/phases. Analysis of trend, night time dispersion, and night time fluctuation was also carried and several anomalies were detected. Most ionospheric perturbations in these parameters were found in the month?of June, from few days to few weeks prior to the earthquakes. Moreover, we filtered the possible effects due to geomagnetic storms, auroras, and solar activities?using parameters like?Dst index, AE index, and Kp index for analyzing the geomagnetic effects,?and Bz (sigma) index, sunspot numbers, and solar index F10.7 for analyzing the solar activities for the confirmation of anomalies as precursors.
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