Vol 55, No 6 (2019)

The article presents the results of a comprehensive study of seismotectonic, geological-geophysical, geodynamic, and seismological data in the region of the Salsk earthquake of May 22, 2001, M = 4.7, in the low-seismic region of the junction of the Scythian Plate and the East European Platform are presented. The parameters of this earthquake source associated with a deep tectonic structure identified by the microseismic sounding method (MSM) are estimated based on seismological and macroseismic data. The MSM section through the region of the Salsk earthquake was obtained by a submeridional profile about 65 km long across the strike of the Manych deflection zone. It was established that the hypocenter of the 2001 Salsk earthquake was confined to the Salsk fault zone included in the system of the Manych faults. This fault is expressed in a section in the form of a narrow subvertical strip with low seismic wave velocities traced from the Earth’s surface to a depth of more than 40 km. Immediately in the area of the earthquake below a depth of 10 km, the recognized fault zone has a local expansion at the point of transition through the plane when the sedimentary cover contacts with the Proterozoic basement. The assessment of the hypocentral position and source mechanism solution (a gently dipping thrust of the northern side at an angle of 25°–33°) correlates well here with the depth and inclination of the surface of the Proterozoic basement, the elements of which are also traced in the MSM section.

The question of the existence of deep earthquake sources in the Caucasus is extremely important both for solving geodynamics problems, assessing seismic hazard, and seismic zoning of the region. It was previously believed that earthquakes with depths not exceeding 150 km can occur in the Caucasus. However, in recent years, this has become argumentative, reflected in a number of publications. This article shows that in the Caucasus, in addition to crustal earthquakes, rather deep mantle earthquakes also occur. This, in addition to direct determinations, is confirmed by data published in Caucasian earthquake catalogs and bulletins. The presence of deep earthquake sources in the Caucasus significantly changes our views on the regional structure and geotectonics. Obviously, crustal earthquakes dominate in the region’s seismicity, but it is clear that mantle earthquakes also make a significant contribution. The fact that they are fewer than crustal earthquakes in the total number may indicate that the crust is harder and more brittle than the upper mantle. Keywords: earthquakes, hypocenters, catalogs, bulletins

The paper reviews observations of modern crustal movements (MCMs) using global navigation satellite systems (GNSS) at nuclear facilities (NF). In 1995–2002, observations were conducted at geodynamic test sites of the Novovoronezh, Kalinin, and Rostov NPPs. Following the results of GNSS observations, a conclusion was drawn about the stability of the Kalinin NPP test site: it was recommended that design solutions take into account deformation of the Earth’s surface in the north–south direction. The creation of a geodynamic test site for observing the activity of the Rostov NPP area based on GPS technology promoted the passage of a state environmental impact assessment during the launch of the first NPP reactor in 2001. In the construction area of Russia’s first deep-level radioactive waste disposal site (Krasnoyarsk krai), a geodynamic test site was created to observe MCMs, and a methodology was developed for processing and interpreting geodynamic observation data taking into account the large-scale spatiotemporal effect. For the first time, for the area at the junction of the largest tectonic structures—the Siberian Platform and the West Siberian Plate—the rates of horizontal crustal deformations were instrumentally measured and the cyclical nature of the geodynamic regime was established. Observations made in 2010–2016 showed that in 2010–2013, maximum changes in distances between observation points did not exceed 10 mm/year. In 2013–2014, the tectonic regime was activated, manifested by a change in the signs of compressional and extensional strain of the upper crust on the right and left banks of the Yenisei River. The annual rates of maximum change in the lengths of baselines during the activation period reached ±18 mm. The standard horizontal and vertical errors for 2012–2016 were 3.0–3.5 and 6.0–7.4 mm, respectively. To take into account the scale factor, methodological approaches to interpreting the observational data were developed, which made it possible to assess the extent of impact of MCMs on the stability of the natural insulating properties of rock massifs while substantiating the geoecological safety of radioactive waste disposal. Based on the observation results, the boundary conditions for modeling the stress–strain state of a rock massif were established and the site of the GKhK Mining and Chemical Combine was geodynamically zoned.

Analytical elevation models use functional dependences to describe heights on the Earth’s surface. This type of relief models can be used in various fields, e.g., geomorphology, gravimetry, and cartography. The main aim of this article is to assess the possibility of using analytical models to describe relief forms of varying complexity: mountains, hills, and plains. For three regions of Spain, we have constructed modified S-approximations of the function describing the relief of the Earth’s surface and analyzed the dependence of the model parameters on the degree of dissection of the relief.

Modern methods of studying the Earth’s gravity field on a mobile base are discussed, among them aerogravimetric research. The features of creating a highly autonomous airborne gravimetric laboratory with a long flight duration for operations in remote territories and waters are described. The experience of creating an airborne laboratory based on AN-30D and AN-26BL aircraft is discussed in detail. The makeup of gravimetric and navigation equipment is substantiated; the need for installing additional thermal and vibration protection devices, backup power lines, and additional communication facilities is shown; and the device and operation of airborne gravimetric systems based on different principles of operation are considered. The aerogravimetric survey method and features of its implementation are discussed. The main provisions of the software packages for in situ and office processing of gravimetric and navigation information obtained both on board the aircraft and at GPS or GLONASS base (ground) stations are presented. Methods for taking into account corrections for aerogravimetric systems with different operating principles are discussed.