Control of variations in the stress-strain state based on monitoring the apparent resistivity in the well

The article gives an example of the application of a new approach to the search for short-term earthquake precursors based on the analysis of the data of three-year monitoring of the apparent resistivity in a water-saturated well on board a reservoir near a hydroelectric power station. The analysis also involved data on atmospheric pressure, water level and temperature in the well. The effects were estimated in a linear approximation, neglecting transients. The method of principal components was used for data processing. The results obtained in the time and frequency domains indicate that a new method for controlling localization variations and searching for short-term precursors of earthquakes is promising.

Occurrence of anomalies in soil radon volume activity before tectonic earthquakes

Research subject. Earthquakes are a global problem for the entire world population. Therefore, a search for ways to predict and prevent tectonic events is a highly relevant task. Despite the existence of controversial opinions on the possibility of predicting tectonic earthquakes, research in this direction continues. Among numerous possible precursors of earthquakes, anomalies in the volume radon activity (VRA) are the most physically justifed ones. The aim of this research was to compare the observed anomalies of soil radon with the recorded seismic events in order to fnd common patterns. The research area was the Kuril Islands. VRA monitoring was conducted at the South Kuril Geophysical Station of the Institute of Marine Geology and Geophysics of the Far Eastern Branch of the Russian Academy of Sciences.Methods and materials. Measurements were carried out in the advective mode: soil air from a depth of 70 cm was forcibly delivered to the detector using a pump. For a retrospective analysis, we took registered seismic events with a magnitude greater than 4 that occurred within a radius of 500 km from the monitoring station in Yuzhno-Kurilsk during 2011–2018. Statistical data were processed using Microsoft Excel, Statistica software. Results. A method for comparing radon anomalies and earthquakes was developed. Using the developed methodology, it was found that the geodynamic criterion of ≥2 (the ratio of earthquake magnitude to logarithm of distance from event epicenter to the monitoring station in km) can be used when comparing VRA anomalies with tectonic earthquakes. Out of the 166 considered tectonic earthquakes meeting the geodynamic criterion of ≥2.148, the events were preceded by VRA anomalies. The position of the earthquakes was determined relative to the extremum of previous anomalous radon values in the time interval. Eac of the considered earthquakes meeting the geodynamic criterion ≥2, which had been preceded by a radon anomaly, occurred either after its extremum or coincided with it in time. Conclusions. The manifestation of tectonic earthquakes in VRA anomalies after passing the extremum can be considered as a short-term prognostic criterion and be used for distinguishing between “near” and “far” events.

Hydrogeological precursors of earthquakes and volcanic activations according to observation data in Kamchatka Peninsula wells

The purpose of the study is generalization of data on the manifestations of hydrogeological earthquake precursors and volcanic activations based on long-term observations in the wells of the eastern part of the Kamchatka Peninsula. The main problem under consideration is the connection between the manifestations of hydrogeological precursors in several wells with the values of the magnitude Mw and epicentral distance of earthquakes to the wells de as well as with the parameters of seismic action in the observation area including specific density of seismic wave energy e and macroseismic intensity of shaking IMSK-64. The study results revealed that hydrogeological precursors in two-four wells had been manifesting for the period from 1 to 9 months before the strongest earthquakes with Mw = 6.6–7.8 at the epicentral distances de = 90–300 km. Such earthquakes were accompanied by the shakings of the intensity of IMSK-64 = 4–6 points. The specific density of seismic energy under such earthquakes was minimum 0.1 J/m3. The hydrogeological precursors were confined to the area for which the ratios of the earthquake epicentral distance de to the maximum linear size of the earthquake source L, km ranged from 1 to 3.7. Using the established relationships between the manifestations of hydrogeological precursors and earthquake parameters, weekly prognostic conclusions were made for expert earthquake prediction councils based on the data of current observations in wells. The well located at the distance of 15 and 20 km from the Koryaksky and Avacha active volcanoes featured the anomalous rise of groundwater pressure before the eruptions in 1991 and 2008– 2009. Therefore, a conclusion can be drawn that observation equipment operating in wells, the study results of hydrogeological precursors of earthquakes and volcanic eruptions as well as their application experience in the work of expert councils can form the scientific and technical basis for the development of geoinformation prediction technology for natural disasters in the Kamchatka Krai.

Reduction of the VLF Signal Phase Noise Before Earthquakes

In this paper we analyse temporal variations of the phase of a very low frequency (VLF) signal, used for the lower ionosphere monitoring, in periods around four earthquakes (EQs) with magnitude greater than 4. We provide two analyses in time and frequency domains. First, we analyse time evolution of the phase noise. And second, we examine variations of the frequency spectrum using Fast Fourier Transform (FFT) in order to detect hydrodynamic wave excitations and attenuations. This study follows a previous investigation which indicated the noise amplitude reduction, and excitations and attenuations of the hydrodynamic waves less than one hour before the considered EQ events as a new potential ionospheric precursors of earthquakes. We analyse the phase of the ICV VLF transmitter signal emitted in Italy recorded in Serbia in time periods around four earthquakes occurred on 3, 4 and 9 November 2010 which are the most intensive earthquakes analysed in the previous study. The obtained results indicate very similar changes in the noise of phase and amplitude, and show an agreement in recorded acoustic wave excitations. However, properties in the obtained wave attenuation characteristics are different for these two signal parameters.

Variations of ionospheric and geomagnetic field parameters during the June 18, 2013 Bachat earthquake

The paper presents the results of a study of variations in ionospheric parameters and local magnetic constant before, during, and after the Вachat earthquake, which occurred on June 18, 2013 at 23:02 UT (June 19, 2013 at 06:02 LT) with a magnitude 5.3–5.6 and epicenter coordinates 54.29° N, 86.17° E. We have used data from IPGG SB RAS and TSU ionospheric stations and INTERMAGNET geomagnetic observatories. We have established that in the period preceding the earthquake there was a rather sharp increase in the magnetic moment, and in the subsequent period there was an equally sharp decrease in the magnetic moment. It is noted that the analysis of the daily average values of the local magnetic constant is the most promising for searching for geomagnetic precursors of earthquakes. We have found a low strong sporadic layer Es for two days before the event, the like of which was not observed for 15 days before and 15 days after the event. In addition, on the days preceding the shock, the background values of the F2-layer critical frequency were larger by more than 20 % at the local pre-event hours. On the second day after the earthquake, there appeared a night-time region of low values (about 14 %), which persisted until the morning of the third day.

Variations of ionospheric and geomagnetic field parameters during the June 18, 2013 Bachat earthquake

The paper presents the results of a study of variations in ionospheric parameters and local magnetic constant before, during, and after the Vachat earthquake, which occurred on June 18, 2013 at 23:02 UT (June 19, 2013 at 06:02 LT) with a magnitude 5.3–5.6 and epicenter coordinates 54.29 ° N, 86.17 ° E. We have used data from IPGG SB RAS and TSU ionospheric stations and INTERMAGNET geomagnetic observatories. We have established that in the period preceding the earthquake there was a rather sharp increase in the magnetic moment, and in the subsequent period there was an equally sharp decrease in the magnetic moment. It is noted that the analysis of the daily average values ​​of the local magnetic constant is the most promising for searching for geomagnetic precursors of earthquakes. We have found a low strong sporadic layer Es for two days before the event, the like of which was not observed for 15 days before and 15 days after the event. In addition, on the days preceding the shock, the background values ​​of the F2-layer critical frequency were larger by more than 20% at the local pre-event hours. On the second day after the earthquake, there appeared a night-time region of low values ​​(about 14%), which persisted until the morning of the third day.

Ionospheric precursors of earthquakes from satellites

<p>In-situ magnetic field and electron density, as observed by Swarm and CSES satellites, are analyzed to identify possible anomalies in geomagnetic quiet time with respect to the ionospheric background. To avoid detecting possible anomalies induced by auroral activity we investigate regions between +50 and -50 degrees in magnetic latitude. Then a superposed epoch and space approach is applied to this anomaly dataset with respect to their time and space distance from shallow M5.5+ earthquakes occurred in about last 6 years. A comparison with analogous homogeneous random distribution of anomalies shows that the real anomaly concentrations found before the occurrence of earthquakes are statistically significant. In addition, we find that, in general, the anticipation times of the ionospheric precursors scale with the earthquake magnitude, confirming the validity of the Rikitake law for ionospheric signals, previously valid for ground precursors. We also find that the anomaly duration seems to depend on the magnitude of the impending earthquake. Finally, we propose a simple scheme of potential earthquake forecast on the base of the previously mentioned characteristics.</p>

Automatic Recognition of Power Line Harmonic Radiation Observed by the EFD On board the ZH-1 Satellite

<p>The power line harmonic generated by human activities can be found from the vast amount of the data observed by EFD on board the ZH-1 satellite. To study the human activities and remove the nonnegligible amount of interferences in the study of ionospheric precursors of earthquakes, we are desperate for finding the power line harmonic from the vast amount of data Hence, a novel automatic power line recognition method is proposed. Firstly, we utilize fourier transform on EFD data to obtain the power spectral density(PSD). Secondly, it is well known that harmonic radiation from power lines presents one or more horizontal linear characteristics on the PSD image and the color of the line is close to the color of the background in the image.In order to highlight the color contrast between the line and the background, we transform the PSD image from the RGB to the HSV color space and utilize the Saturation compoment of the HSV space as the object image.To obtain the edge regions, we process the object image with canny techniques. Finally, we use the Hough transform to detect the power line from the edge regions. To evaluate the proposed method, the experiment is performed for the dataset composed of 100 PSD images and each PSD image includes several interference lines. And the experimental result verifies the effectiveness of the proposed method with an accuracy of 86%.</p>

A possible radio anomaly observed on the occasion of the MW=6.0 earthquake occurred in Dodecanese islands at the end of January 2020

<p>Since 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<br>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 5<sup>th</sup> 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.</p><p>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.2019.82007</p>