Technogenic-tectonic earthquakes of the Dnieper–Donets aulacogen

The Mikhnevo Seismic Group of the Institute of Geosphere Dynamics, Russian Academy of Sciences (IGD RAS), and the Malin mini-group in the region of the Dnieper–Donets aulacogen, within which prospecting and mountain-explosion works were carried out from 2007 to 2015 on industrial scales, recorded a series of seismic events. Special attention has been focused on analysis of the nature of three earthquakes in 2015. Application of the spectral discrimination method log(Pg/Lg) and cross-correlation tools allowed us to identify the seismic events in 2015 as a special technogenic-tectonic type.     

The Deep Velocity Structure of the Central Kola Peninsula Obtained using the Receiver Function Technique

Doklady Earth Sciences - New results are presented on the features of the deep velocity structure of two of the three main tectonic blocks that make up the Kola region—Murmansk and...     

Cavitation separation of nano-and microscale monomineral fractions from polymineral microparticles

Possible cavitation disintegration of polymineral microparticles placed into a liquid as a result of interaction of particles with collapsed cavitation bubbles is shown for the minerals most abundant in gold ore. The bubbles are generated by shock loading of the liquid heated to the boiling temperature. The possibility of cavitation separation of nano-and microscale monomineral fractions from polymineral microparticles is demonstrated.     

Analysis of Russian Hydroacoustic Data for CTBT Monitoring

—?As part of a collaborative research program for the purpose of monitoring the Comprehensive Nuclear-Test-Ban Treaty (CTBT), we are in the process of examining and analyzing hydroacoustic data from underwater explosions conducted in the former Soviet Union. We are using these data as constraints on modeling the hydroacoustic source as a function of depth below the water surface. This is of interest to the CTBT because although even small explosions at depth generate signals easily observable at large distances, the hydroacoustic source amplitude decreases as the source approaches the surface. Consequently, explosions in the ocean will be more difficult to identify if they are on or near the ocean surface. We are particularly interested in records featuring various combinations of depths of explosion, and distances and depths of recording.¶Unique historical Russian data sets have now become available from test explosions of 100-kg TNT cast spherical charges in a shallow reservoir (87?m length, 25?m to 55?m width, and 3?m depth) with a low-velocity air-saturated layer of sand on the bottom. A number of tests were conducted with varying water level and charge depths. Pressure measurements were taken at varying depths and horizontal distances in the water. The available data include measurements of peak pressures from all explosions and digitized pressure-time histories from some of them. A reduction of peak pressure by about 60–70% is observed in these measurements for half-immersed charges as compared with deeper explosions. In addition, several peak-pressure measurements are also available from a 1957 underwater nuclear explosion (yield <10?kt and depth 30?m) in the Bay of Chernaya (Novaya Zemlya).¶The 100-kg TNT data were compared with model predictions. Shockwave modeling is based on spherical wave propagation and finite element calculations, constrained by empirical data from US underwater chemical and nuclear tests. Modeling was performed for digitized pressure-time histories from two fully-immersed explosions and one explosion of a half-immersed charge, as well as for the peak-pressure measurements from all explosions carried out in the reservoir with water level at its maximum (3?m). We found that the model predictions match the Russian data well.¶Peak-pressure measurements and pressure-time histories were simulated at 10?km distance from hypothetical 1-kt and 10-kt nuclear explosions conducted at various depths in the ocean. The ocean water was characterized by a realistic sound velocity profile featuring a velocity minimum at 700?m depth. Simulated measurements at that same depth predict at least a tenfold increase in peak pressures from explosions in the SOFAR channel as compared with very shallow explosions (e.g., ～3?m depth).¶ The observations and the modeling results were also compared with predictions calculated at the Lawrence Livermore National Laboratory using a different modeling approach. All results suggest that although the coupling is reduced for very shallow explosions, a shallow 1-kt explosion should be detectable by the IMS hydroacoustic network.     

Impact of Natural Extreme Events on Geophysical Fields in the Environment

Izvestiya, Physics of the Solid Earth - Abstract—The effects of the strong natural events on the acoustic fields in the atmosphere, geomagnetic field, and electrical characteristics of...     

Identification of Induced Seismicity in the Fault Zone of the Korobkovskoye Deposits (Kursk Magnetic Anomaly) Based on Observations of a Small-Aperture Seismic Array

Doklady Earth Sciences - The results of recording and determining the locations of seismic events triggered by industrial explosions conducted by OJSC Kombinat KMAruda at the Korobkovskoe iron ore...     

Study of neotectonic activity of morphostructures in the central part of the east european craton by remote sensing methods

The combined approach is used for studying recent tectonic activity in the central part of the East European Craton (EEC).This approach incorporates the methods of automated lineament analysis and satellite geodesy with the conventional geological mapping analysis. The space tectonic map (space image based) is reconstructed, and morphostructures that are active at the recent and present tectonic stage are delineated by processing the Landsat image mosaic. The direction and rate of horizontal displacement of crustal blocks, which is caused by deep geodynamical processes, are determined using the GPS data. The study is preliminary since only few GPS stations within the EEC have sufficiently long time series of observations.     

Near-surface geophysics: Complex investigations of the lithosphere-atmosphere interactions

The key trends and problems in the study of interactions between the geospheres in the near-surface areas of the continental crust of the Earth which are of most interest for the formation of living environment are formulated. The main periodicities in the variations of geophysical fields determining the natural environmental rhythms are determined. The interactions and transformations of geophysical fields (electric field in the ground and in the atmosphere, radon emanation field, and the field of microseismic vibrations) are considered. It is noted that the tectonic discontinuities and weak disturbances in the solid Earth such as lunar-solar tides and variations in the atmospheric pressure play an important role in the formation of the regimes of geophysical fields at the boundary of the Earth’s crust and the atmosphere. The synchronous instrumental observations reveal a mutual influence and significant correlation between the amplitude variations of geophysical fields of different nature.     

Remote detection of aftershock activity as a new method of seismic monitoring

A weak seismic event with body wave magnitude 2.1 was detected near the epicenter of an underground explosion conducted by the Democratic People’s Republic of Korea (DPRK) on September 9, 2016. The event occurred approximately two days after the test. Using the method of waveform cross-correlation, two array stations of the International Monitoring System (IMS), USRK and KSRS, recorded the arrival of P _n waves. At the same time, this event was not recorded during the standard automatic processing at the International Data Center. The location and other characteristics of this weak event indicate that it is likely to have been an aftershock of the preceding explosion. Based on the successful automatic detection and construction of the event, we conducted an extended investigation, which consisted in searching for secondary seismic phases at the nearest stations that do not belong to the International Monitoring System. The final solution, which is based on waveform cross-correlation, includes stations MDJ (China) and SEHB (Republic of Korea), the aftershock epicenter is located at ~2 km northwest of the epicenter of the DPRK test.