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Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia
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- PublicationOpen AccessSelf-oscillations in rocks,results of laboratory experiments(2004)
; ; ; ; ;Kamshilin, A. N.; Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia ;Volkova, E. N.; Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia ;Kuzichkin, O. R.; Muromsky Institute, Vladimir Region, Russia ;Sokolnikov, M. A.; Muromsky Institute, Vladimir Region, Russia; ; ; The method of generation of self-oscillations in rocks is developed here. Self-oscillations arise as a result of direct and inverse mechanoelectric transformations without an external generator. Laboratory experiments were executed with different samples. A relation between self-oscillation parameters from samples humidity and direct electrical field applied to samples was detected.114 189 - PublicationOpen AccessSeasonal variations in natural processesand atmospheric precipitation(2004)
; ; ;Descherevsky, A. V.; Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia ;Ya. Sidorin, A.; Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia; To study the nature of seasonal variations in time series measured at the Garm test site, a local model based on the experimental data of atmospheric precipitation penetration into the soil has been proposed. It is intended for filtration of exogenous variations in the data of various time series and a study of statistical structure of different natural processes, including earthquake preparation processes, and the mechanisms of their effect on the biosphere. Using this model, we analyze and compare variations in apparent resistivity and properties of rock moistening. It has been shown that at small current-electrode (AB) separations among all the parameters of water regime, only water saturation of the active soil layer reveals a significant correlation with apparent resistivity variations. When increasing the current-electrode separation, the seasonal variation form varies from quasisinusoidal in the upper layer up to quasi-triangular at the largest investigated depths (maximum separations).187 342 - PublicationOpen AccessThe study of local sources of ULF geoelectric signals with steep fronts(2004)
; ;Chirkov, Y. B.; Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, RussiaThe method for recognition and monitoring of ULF electrotelluric signals with steep fronts is presented. The method is based on the multicomponent measurements of the geoelectric field and recognition of the clusters of signals using the data of spatial-polarization filtering. This detects the local sources of the signals associated with the variation of mode of deformation of the medium. The method was applied to the study of geoelectric sources associated with aftershocks of the Racha-Djava earthquake. The field observations show with a fair degree of confidence that these signals are generated by a small number of local zones in the vicinity of the observer (at a range of tens-hundreds meters). The spatial distribution and the dynamic properties of the local sources are described. The analysis of observations leads to the conclusion that the dynamics of the local sources of ULF signals with steep fronts may be considered possible electrotelluric precursors of the earthquakes. Consideration is given to the feasibility of the well-known VAN method for earthquake prediction. The overall methodological aspects of the current studies of the electrotelluric precursors of the earthquakes are discussed.86 155 - PublicationOpen AccessPreseismic ULF effectand possible interpretation(2004)
; ; ; ; ; ; ;Molchanov, O. A.; Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia ;Yu. Schekotov, A.; Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia ;Fedorov, E.; Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia ;Belyaev, G. G.; Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation (IZMIRAN), Russian Academy of Science, Troitsk (Moscow Region), Russia ;Solovieva, M. S.; Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia ;Hayakawa, M.; The University of Electro-Communications, Chofugaoka, Chofu, Tokyo, Japan; ; ; ; ; We present the results of ULF magnetic field observation at Karimshino station (Kamchatka, Russia). Using a case study we discovered an effect of suppression of ULF intensity about 2-6 days before rather strong and isolated seismic shocks (magnitude M = 4.6-6.6). It is revealed for nighttime and the horizontal component of ULF field (G) in the frequency range 0.01-0.1 Hz. Then we prove the reliability of the effect by computed correlation between G (or 1/G) and especially calculated seismic indexes Ks for the rather long period of observation from June 2000 to November 2001. Our recent data confirm the validity of the effect. We show here a similar result during a period of frequent strong seismic activity in April-May 2002. It is highly probable that the effect observed is connected with the increase in plasma density perturbations inside the ionosphere, which are induced by preseismic water and gas release at the ground surface and following energy transportation into the ionosphere by atmospheric gravity waves. Two models are discussed and computed: the first is a decrease of penetration coefficient of Alfven waves from the magnetosphere due to a turbulent increase in effective Pedersen conductivity in the ionosphere, and the second is a change in wave number (k) distribution of source ionospheric turbulence. One of the mechanisms or both could be responsible for the observed 2-3 times suppression of ULF magnetic field noise at the ground.152 131 - PublicationOpen AccessSpatial-temporal structure of seismicity of the North Tien Shan and its changeunder effect of high energy electromagnetic pulses(2004)
; ; ;Tarasov, N. T.; Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia ;Tarasova, N. V.; Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia; The effect of high-energy electromagnetic pulses emitted by a magnetohydrodynamic generator used as a source for deep electrical sounding of the crust on spatial-temporal structure of seismicity of the North Tien Shan is explored. Five-six years periodicity of changes in spatial distribution of seismicity was revealed. The effect of electromagnetic pulses increases the stability of the spatial distribution of seismicity over time and simultaneously speeds up cycles of its transformations, which develop on stabilization background. Increasing of seismic energy release after electromagnetic impacts is observed basically in most active zones. Periodic variation of efficiency of earthquakes triggering on the distance to the MHD-generator was detected. It was shown that electromagnetic pulses give rise to an appreciable increase in the rate of local earthquakes, occurring around 2-6 days after the pulses. Total earthquakes energy released after start-ups was by 2.03·1015 J greater than the energy released before them. At the same time, the total energy transmitted by the MHD-generator was 1.1·109 J, i.e. six orders of magnitude smaller. Consequently, the electromagnetic pulses initiated the release of the energy that had been stored in the crust due to activity of natural tectonic processes in the form of comparatively small earthquakes, which leads to an additional release of tectonic stresses.181 256 - PublicationOpen AccessDepression of the ULF geomagnetic pulsation related to ionospheric irregularities(2004)
; ; ; ; ; ;Sorokin, V. M.; Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation (IZMIRAN), Russian Academy of Science, Troitsk (Moscow Region), Russia ;Fedorov, E. N.; Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia ;Yu. Schekotov, A.; Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia ;Molchanov, O. A.; Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia ;Hayakawa, M.; Department of Electronic Engineering, The University of Electro-Communications, Tokyo, Japan; ; ; ; We consider a depression in intensity of ULF magnetic pulsations, which is observed on the ground surface due to appearance of the irregularities in the ionosphere. It is supposed that oblique Alfven waves in the ULF frequency range are downgoing from the magnetosphere and the horizontal irregularities of ionospheric conductivity are created by upgoing atmospheric gravity waves from seismic source. Unlike the companion paper by Molchanov et al. (2003), we used a simple model of the ionospheric layer but took into consideration the lateral inhomogeneity of the perturbation region in the ionosphere. It is shown that ULF intensity could be essentially decreased for frequencies f = 0.001-0.1 Hz at nighttime but the change is negligible at daytime in coincidence with observational results.153 195 - PublicationOpen AccessState-of-the-art of historical earthquake research in Fennoscandia and the Baltic Republics(2004)
; ; ; ; ; ; ;Mäntyniemi, P.; Institute of Seismology, University of Helsinki, Finland ;Husebye, E. S.; Department of Earth Science, University of Bergen, Norway ;Kebeasy, T. R. M.; Department of Earth Science, University of Bergen, Norway ;Nikonov, A. A.; Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia ;Nikulin, V.; State Geological Survey of Latvia, Riga, Latvia ;Pacesa, A.; Geological Survey of Lithuania, Vilnius, Lithuania; ; ; ; ; We review historical earthquake research in Northern Europe. 'Historical' is defined as being identical with seismic events occurring in the pre-instrumental and early instrumental periods between 1073 and the mid-1960s. The first seismographs in this region were installed in Uppsala, Sweden and Bergen, Norway in 1904-1905, but these mechanical pendulum instruments were broad band and amplification factors were modest at around 500. Until the 1960s few modern short period electromagnetic seismographs were deployed. Scientific earthquake studies in this region began during the first decades of the 1800s, while the systematic use of macroseismic questionnaires commenced at the end of that century. Basic research efforts have vigorously been pursued from the 1970s onwards because of the mandatory seismic risk studies for commissioning nuclear power plants in Sweden, Finland, NW Russia, Kola and installations of huge oil platforms in the North Sea. The most comprehensive earthquake database currently available for Northern Europe is the FENCAT catalogue covering about six centuries and representing the accumulation of work conducted by many scientists during the last 200 years. This catalogue is given in parametric form, while original macroseismic observations and intensity maps for the largest earthquakes can be found in various national publications, often in local languages. No database giving intensity data points exists in computerized form for the region. The FENCAT catalogue still contains some spurious events of various kinds but more serious are some recent claims that some of the presumed largest historical earthquakes have been assigned too large magnitude values, which would have implications for earthquake hazard levels implemented in national building codes. We discuss future cooperative measures such as establishing macroseismic data archives as a means for promoting further research on historical earthquakes in Northern Europe.170 852 - PublicationOpen AccessBackground electromagnetic noisein the vicinity 1 Hz as a possible indicatorof earthquake-related anomalies(2004)
; ;Gokhberg, M. B.; Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, RussiaMeasurements of space-time distributions of the background emissions in the frequency range 0.5-5 Hz and their seasonal and diurnal variations are presented. The analysis of impedance ratio determines the presence of high space harmonics in the emission spectral distribution. The absence of this emission during the winter time correlates with the absence of any precursors before local earthquakes with M ~ 6. It is shown that the knowledge of the background emission behavior and its origin are very important for precursor phenomena monitoring.139 196 - PublicationOpen AccessLow velocity and low electricalresistivity layers in the middle crust(2004)
; ;Pavlenkova, N. I.; Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, RussiaSome Deep Seismic Sounding (DSS) revealed low velocity layers in the upper and middle crust of old platforms. The layers are often characterised by a lower electrical resistivity. It is not clear, however, how reliable the layers recognized from DSS data are, if they are regular or occasional events and how they correlate with other geophysical parameters. To answer these questions the experimental DSS data obtained in the Baltic and Ukranian shields by different institutions were reinterpreted by the author with unified methods. The shield areas are well studied using both the DSS and high-frequency magnetotelluric sounding (MTS) methods. As a result a marked velocity inversion (waveguide) was observed in a 10 to 20 km depth range in the majority of the DSS profiles. An increase in the electrical conductivity is typical for the waveguide. A comparison of the results with the data from other platform regions allow the conclusion that this low velocity and high electrical conductivity layer has a global significance. In the continental crust, the layer is characterised by changes in the reflectivity pattern, earthquakes number and changes in velocity pattern where the block structure is transformed into a subhorizontal layering. These structural features suggest that the layers separate brittle and weak parts of the crust. Usually they play the role of detachment zones at crustal block moving. A possible factor responsible for this phenomenon is an increase in porosity and in the salinity of the waveguide pore water compared with the upper crust. This suggestion is confirmed by the Kola superdeep borehole data. Porosity increasing in the middle crust is explained by the change in rock mechanical properties with depth, by fracturing porosity and by dilatancy effect, at a depth of 10-20 km.100 490 - PublicationOpen AccessOn the excitation of magnetic signals by Love waves(2004)
; ; ; ;Guglielmi, A. V.; Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia ;Potapov, A. S.; Institute of Solar-Terrestrial Physics, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia ;Tsegmed, B.; Astronomy and Geophysics Research Center, Mongolian Academy of Sciences, Ulaanbaatar, Mongolia; ; The polarization method for recognition of seismomagnetic waves against a noise background is presented. The method is applied to detection of magnetic oscillations accompanying the propagation of surface Love wave after a strong earthquake. A specific property of the Love waves is that theoretically the Tolman-Stewart effect is alone responsible for the magnetic field that penetrates into the Earth's surface. Data from the Mondy Magnetic Observatory and the Talaya Seismic Station suggest that the arrival time, duration, period,and polarization of magnetic signals conform with the idea of generation of alternating electric currents due to fluid vibrations in pores and fractures of rocks under the action of the inertial force associated with the Love wave propagation.133 206