Observations of crustal tide strains in the Elbrus area

Results of observations of tidal strains of the crust in the tectonically active Elbrus area of the Northern Caucasus carried out with the use of the Baksan SSAI laser interferometer strainmeter over the period from 2003 through 2006 are presented. Harmonic analysis is performed with the help of the ETERNA software package. Statistically significant time variations in the amplitudes of the main tidal waves M ₂ and O ₁ are revealed. The influence of the topography on tidal strains in the Baksan gorge is estimated at 22% (an increase in the measured strain values). The reduced amplitude factors of the main diurnal (O ₁) and semidiurnal (M ₂) waves are underestimated. Numerical modeling of tidal anomalies produced by regional heterogeneous inclusions is performed in a 2-D approximation. The observed anomaly of the M ₂ wave (12%) is shown to be due to the influence of the main magma-controlling fault associated with the deep magma source of the Elbrus dormant volcano.     

Earth’s Free Oscillations Excited by the 2013 Okhotsk Sea Earthquake

Izvestiya, Atmospheric and Oceanic Physics - Based on the deformation data measured by the Baksan laser interferometer-strainmeter, Earth’s free oscillations (EFO) excited by the Okhotsk Sea...     

Modern Horizontal Movements in the Zones of Strong and Moderate Earthquakes of the Early 21st Century in the Central Sector of the Greater Caucasus: Characteristics Inferred from GPS Observations and Connection with Neotectonics and Deep Structure of the Earth’s Crust

Izvestiya, Atmospheric and Oceanic Physics - Analysis of GPS-measurements made for the first time along the geodesic profile crossing all the main geological structures in the Ossetian region of...     

Relativistic Reductions in High-Precision Measurements of the Earth’s Global Gravity Field Using a Multipair Constellation

Astronomy Reports - The theory of relativistic reductions for future challenges of space gravimetry with target accuracy of up to 1 picometer is developed in this paper.     

Selective Manifestation of Sesmogenic Stress Field within the Mediterranean Belt (Based on Earthquake Focal Mechanism Solutions)

Separate domains of the Mediterranean belt (Zagros, Vrancea, and the Crimea-Caucasus-Black-Sea region) are discussed to argue for a diversity of earthquake-generation mechanisms as an impact of very variable systems of tectonic stresses, which are at the same time characterized by selectiveness in the orientations of the principal axis. We give stereographic models of earthquake-generation mechanisms, as well as the results from parameterization and structural kinematic identification of elements in the internal structure of seismogenic regions. We have identified a discrete character of earthquake-generating stress fields both with respect to the cardinal points (to the Earth’s axis of rotation) and with respect to the ground (horizontal) surface. We show that the diversity of seismogenic settings results from the transformations of stress fields that occur both at the regional and at local levels in the zones affected by the impact of major seismogenic structures in the study regions.     

Satellite geodetic monitoring of the Vladikavkaz active fault zone: First results

A geodetic network of Global Satellite Navigation System (GNSS) observation sites was organized in 2014–2015 for studying the contemporary crustal motions in the zone of the Vladikavkaz deep fault (Milyukov et al., 2014; 2015). The measurements were conducted and the first velocity estimates obtained testifying to the consistency of crustal motions in the Vladikavkaz fault zone and the Ossetian region overall in the ITRG2008 system. The first results show that the velocities and directions of horizontal motions do not change upon the transition of the fault zone. In correspondence with the northeastern orientation of the site displacement vectors and sublatitudinal trend of the disjunctive zone, the presence of left-lateral strike-slip displacements along the branches of an active fault should be expected. However, the signs pointing to the activation of motion in the fault zone are absent. Besides, even the manifestation of weak seismicity has not been observed within the high-magnitude seismogenic Vladikavkaz zone associated with this fault for more than 25 years. This suggests the passive present state of this structure, one of the largest disjunctive structures of the Northern Caucasus. In order to verify this conclusion and revealing the kinematic pattern of the displacements associated with the fault structure it is reasonable to continue the measurements.     

“Galileo Galilei” (GG) a small satellite to test the equivalence principle of Galileo, Newton and Einstein

“Galileo Galilei” (GG) is a small satellite designed to fly in low Earth orbit with the goal of testing the Equivalence Principle—which is at the basis of the General Theory of Relativity—to 1 part in 10¹⁷. If successful, it would improve current laboratory results by 4 orders of magnitude. A confirmation would strongly constrain theories; proof of violation is believed to lead to a scientific revolution. The experiment design allows it to be carried out at ambient temperature inside a small 1-axis stabilized satellite (250 kg total mass). GG is under investigation at Phase A-2 level by ASI (Agenzia Spaziale Italiana) at Thales Alenia Space in Torino, while a laboratory prototype (known as GGG) is operational at INFN laboratories in Pisa, supported by INFN (Istituto Nazionale di fisica Nucleare) and ASI. A final study report will be published in 2009.     

Detection and Evaluation of the Slichter Mode Based on Long-Term Strain Observations

Izvestiya, Atmospheric and Oceanic Physics - To search for the Slichter mode (1S1), the longest mode of Earth’s free oscillations, long-term (more than 15 years) strain data of the Baksan...     

TianQin Space-Based Gravitational Wave Detector: Key Technologies and Current State of Implementation

Astronomy Reports - TianQin is a project of a space-based gravitational wave detector for detecting GW events in the millihertz frequency range. The space-based detector must be implemented on...     

Oceanic Loading and Local Distortions at the Baksan,Russia, and Gran Sasso,Italy, Strain Stations

Reliable use of strain data in geophysical studies requires their preliminary correction for ocean loading and various local distortions. These effects, in turn, can be estimated from the tidal records which are contributed by solid and oceanic loading. In this work, we estimate the oceanic tidal loading at two European strain stations (Baksan, Russia, and Gran Sasso, Italy) by analyzing the results obtained with the different Earth and ocean models. The influence of local distortions on the strain measurements at the two stations is estimated.