Large Earthquake Prediction Methods

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.

The INFREP Network: Present Situation and Recent Results

VLF/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.