A. V. Nikolaev

Deep structure and volcanic activity of Mount Elbrus and a portion of the Elbrus–Tyrnyauz valley: Geological and geophysical data

A microseismic sounding profile was made along the Baksan River valley from the eastern summit of Elbrus volcano to the southern edge of town Tyrnyauz. The geological section along the profile presents the structural features of the subaerial structure of Mount Elbrus and magmatic chambers, which are traced to a depth of 40 km or more as a subvertical chain. Along the profile, deep-seated faults, well correlated with their morphological manifestations on the surface, were identified. Under the southern edge of town Tyrnyauz, a low-velocity region, comparable in size to Elbrus volcano, was interpreted as the cooling volcanic structure. The results obtained were correlated with the data available on the geology and geomorphology of the area of study, as well as data obtained earlier during independent studies of Elbrus volcano.

New possibilities of combined data processing from recording of displacements and strains in the field of seismic waves

The results of analysis of the motion of an elementary fragment of an elastic deforming body (geoblock) have shown that description of the geoblock by combined temporal and spatial derivatives and instrumental monitoring with the movement sensors (seismiographs) and strain sensors (deformographs) are the most acceptable and informative methods.

Instrumental study of high-frequency seismoacoustic signal modulation in a deep drillhole

For many years we have failed to record instrumentally the background variations in seismoacoustic emission in solid consolidated rocks of the Earth’s crust at great depths (3200 m) and to confirm their relation to lunar-solar gravitation. We managed to fulfill the task only with significantly improved parameters of the recording system measurement channel. As follows from analysis of new data, the amplitudes in the diurnal cycle vary from 1930 to 2100 fm (10−15) for the band of 160 Hz and from 129.5 to 132 fm for the band of 500 Hz, while the energy model correlation coefficients are within 0.737–0.852. Hence, this fact proves once again that background variations related to lunar-solar tides are universal in occurrence, and their frequency and amplitude depend significantly on the host rocks, position, and time of observations, while the energy model fits in these variations.

The van earthquake on October 23, 2011: Natural and technogenic causes

A measurable effect of mass bombing on weak to moderate seismicity, endogenous microseism intensity, and acceleration of tectonic processes has been found. This effect is seen in the regime of strong and catastrophic earthquakes, a decrease in magnitude and time for their preparation, and lesser seismic hazard. The M = 7.8 Van Earthquake on October 23, 2011, was induced to occur early due to mass bombing in Libya and other regions of North Africa; however, the induced character caused its magnitude to be less by several tenths than it might have been.

What happens in the Earth’s crust between sunset and sunrise?

673 The overwhelming majority of processes on the Earth have a diurnal cycle, which is related in one way or another to the Sun. In any case, if not the processes, then their time variability is related to the rhythm of the interaction between the Earth and the Sun. There fore, regardless of the widely spread opinion about the dominating influence of the Moon on the hydroa coustic processes in the Earth’s crust, we studied, first of all, the correlation of the seismoacoustic processes in the upper part of the Earth’s crust with the influence of the Sun. It was found that the deformation pro cesses in the Earth’s crust related to the Sun’s gravita What Happens in the Earth’s Crust between Sunset and Sunrise?

Synchronization of seismoacoustic emission with deformation of the earth's upper crust

Long-term geoacoustic observations revealed an explicit synchronization in the Earth’s upper crust between the amplitude of acoustic noise at a frequency of 28‐35 Hz, which is related to seismoacoustic emission (SAE), and the calculated value (a squared rate of variation in the volume strain of the earth’s crust due to solar gravitation [1]). A joint study of these two processes, the observed SAE, and the calculated tidal deformation established that the average background seismic noise has a relatively high correlation coefficient (0.6‐0.8) with a solar component of tidal deformation (SD), but lacks stable correlation with the lunar component of tidal deformation (LD) or total deformation due to lunar‐solar tide (LSD). We found out previously that variation in SAE intensity within the mentioned frequency band at a depth of about 2000 m has good agreement (in terms of amplitude and phase) with the rate of variation in lunar‐solar disturbance of gravity [2]. As a result of a posteriori detailed analysis of data obtained in 1988 in a borehole at a depth of 390 m [3], the SAE intensity was found to have the best correlation with the sum of squared rates of variations in volume strain due to solar and lunar gravitation components (LD + SD), i.e., with the total power of the Earth’s tide. It is evident from the cited data that correlation coefficients of SAE intensity and calculated power of individual components of the tidal process in the Earth’s crust are rather significant for LD and SD components, but the correlation coefficient with the squared rate of deformation due to total lunar‐solar gravitation (LSD) yields negative values. This is evident from the following correlation coefficients between SAE and components, as follows:

Velocities of Present-Day Horizontal Movements in the Central Sector of the Greater Caucasus according to GPS Observations and Their Relation to Tectonics and the Deep Structure of the Earth’s Crust

The results of the first GPS measurements along the geophysical profile that intersects all major geological structures of the Osetiya region of the Greater Caucasus are presented. The results of the measurements are interpreted in comparison with those of neotectonic studies and data on the deep structure.

New evidence of acoustic effects of radiation impacts in deep wells

Passive seismic observations were performed in the Vorotolovskaya deep well in Nizhny Novgorod oblast at a depth of 1400 m and in a well in the vicinity of Ufa at a depth of 500 m. Observations show significantly different acoustic impulse fluxes in these wells: hundreds per second in the Vorotilovskaya deep well and only few impulses per day in the Ufa well. It is supposed that it is the geological conditions that determine the character of seismoacoustic signals. A seismic observation technique is proposed for further studies of acoustic manifestations of radiation fields.

Study of acoustic noise on Valaam Island

A long-term endogenous nanomicroseismic event was registered instrumentally for the first time on Valaam Island (Lake Ladoga) in the winter of 2012. In the past, similar events in the form of acoustic emissions of separate phases have occurred from time to time and were heard by many residents and visitors to the island. This emission has long been known as barantida. The identification of the signal was based on a comprehensive analysis of the obtained seismograms and the subjective descriptions of this rare phenomenon by witnesses. It is proposed to continue instrumental observations in the mode of continuous high resolution seismoacoustic monitoring.

Joint analysis of the seismic data and velocity gravity model

We performed joint analysis of the seismic noises recorded at the Japanese Ogasawara station located on Titijima Island in the Philippine Sea using the STS–2 seismograph at the OSW station in the winter period of January 1–15, 2015, over the background of a velocity gravity model. The graphs prove the existence of a cause-and-effect relation between the seismic noise and gravity and allow us to consider it as a desired signal.