Major and Trace Elements in Water and Suspended Matter of the Northern Dvina River and Their Annual Discharge into the White Sea

Oceanology - The results of continuous four-year-long investigations (from May 2015 to April 2019) of the elemental composition of water and suspended matter in the Northern Dvina River are given....     

Present-day stress-strain state in the upper crust of the Amurian lithosphere plate

Consideration is given to the issues of studying current geodynamic processes in the upper crust within the Amurian lithosphere plate. Present-day geodynamic processes in the lithospheric layer are shown to be located by different indicators that correspond to geological features of comparable scale and varying extension and are recognized by a set of investigative techniques. A variety of original data on vertical and horizontal motions of the surface is used to indicate the latest deformation processes. The best studied Trans-Baikal block was used as an example to analyse present-day geodynamics in the context of the tectonic flows conception. The present ideas concerning the stress-strained state of the upper part of the section within the Amurian plate have been refined based on non-uniformly scaled factors.     

Spinner dolphins Stenella longirostris off south-west Mauritius: abundance and residency

Spinner dolphins Stenella longirostris longirostris off the south-west coast of Mauritius are subject to ongoing anthropogenic disturbance in the form of daily dolphin tourism, which has intensified since 1998. Abundance of this species was estimated using photo-identification data and mark-recapture analysis. Between April 2008 and June 2010, identification photographs were collected from dolphins occurring along a 30 km length of the coast of south-west Mauritius. A total of 250 groups were encountered over 229 survey days. Mark-recapture analyses were performed on a photographic dataset of more than 8 000 good- and excellent-quality images and 83 animals were identified as distinctively marked individuals. The majority (85.5%) were seen more than once and resightings indicated a resident population. The compiled version of SOCPROG 2.4 was used to investigate the lagged identification rate. The fitted model supported a mostly resident population with additional animals moving in and out of the study area. The estimated abundance of the total population in the study area ranged between 138 and 399 individuals. Our results can be used for monitoring the population for fluctuations and for encouraging both the enforcement of laws regarding dolphin watching and the development of further means of management needed to ensure the long-term presence of this population.     

USE OF SPACE IMAGERY IN COMPILING ENVIRONMENTAL-PROTECTION MAPS (with reference to the Soligorsk potash-mining district)

The authors apply remote sensing data to the mapping of natural envionment with a focus on environmental protection. The technique is illustrated with particular reference to a largely swampy potash-mining deposit in Belorussia which is the largest potash producer of the USSR, accounting for 54% of its total output in 1983. Translated from: Kartografirovaniye po kosmicheskim snimkam i okhrana okruzhayushchey sredy (Mapping from Space Imagery and Protection of the Environment), edited by Ye. A. Vostokova et al., Moscow: Nedra, 1983, pp. 177-195.     

Seismicity,Tectonics, and GPS Geodynamics of the Caucasus

Izvestiya, Physics of the Solid Earth - The style of the seismotectonic deformation of the Earth’s crust in the Caucasus and its immediate surroundings corresponds to the thrust setting with...     

Calculating the Station Corrections to Earthquake Energy Class and the Acoustic Impedance for Kamchatka Stations

This paper describes a method for calculating the station corrections to earthquake energy class and the acoustic impedance based on records of earthquake codas in the 0.8–1.8 Hz frequency band. The calculation is based on measurements of the relative coda level at two stations, with one of the two being used as the reference. The data were recorded by digital seismometers: CMG-3TB (GURALP), CMG-5TD (GURALP), CMG-6TD (GURALP), and GMS-AC-73i HHV (GeoSIG). We present estimates of class corrections for the Kamchatka network of seismic stations.     

Stability of the multiple star system ι UMa (ADS 7114)

The physical and orbital parameters of the quadruple star system ι UMa (HD 76644 = ADS 7114) were determined earlier, when it was concluded based on modeling the system’s dynamics and applying theoretical stability criteria that the system was probably unstable. Here the stability of the ι UMa system is studied by calculating the Lyapunov characteristic exponents for representative sets of parameters and initial conditions. The conclusions on the system’s stability (or instability) based on various stability criteria and the calculated Lyapunov exponents are compared. The instability of the system as a whole is confirmed rigorously based on massive computations of the Lyapunov exponents. This system appears to be the only known multiple system whose instability has been rigorously established. The Lyapunov time-disruption time statistical relations are constructed, which show that the Hamiltonian intermittency of the second kind dominates. Typical disruption times are shorter than 1000 years, and the Lyapunov times are shorter than 100 years.     

Seasonal and interannual variability of oceanographic conditions in the southwestern part of the Sea of Okhotsk

The seasonal variability of oceanographic conditions in the southern part of the Sea of Okhotsk is described based on long-term mean temperature T and salinity S from observations along a standard oceanographic section Cape Aniva-Cape Dokuchaev (May–November). It is shown that the Soya Current is relatively weak in spring, with low temperature and salinity gradients along the section. The Sea of Okhotsk low-salinity water mass is observed in the upper layer. It was formed as a result of melting of a large amount of ice brought here with the East Sakhalin Current from the northwestern part of the Sea of Okhotsk. A cold intermediate layer (CIL) at depths of 50–150 m extends along the entire section. The cold intermediate layer core with a temperature at the edge of the Sakhalin shelf of about ?1.3°C is retained during a period of maximum warming in August; however, in October–November the intensified flow of the East Sakhalin Current (up to 50 cm/s) results in a situation when relatively warm low-salinity waters, connected with the Amur River runoff, dissipate CIL. The results of 12 surveys conducted by the Sakhalin Research Institute for Fisheries and Oceanography in 1998–2004 show significant deviations of T and S [10] in different years from the calculated values. Generally, maximum anomalies (ΔT > 4°C and ΔS > 0.55‰) are observed in the surface layer. Their values and statistical significance decrease with depth. However, the situation is opposite in some cases. The maximum deviation from normal was observed in June 1999, when warm and salt waters were located much further seaward from the Kunashir shelf, which is most likely connected with the Soya Current meandering.     

Seismotectonic characteristics of the northern flank and axial part of the Tajik Depression (the Garm Geodynamic Research Area)

Detailed estimates of seismotectonic strain (STS) characteristics are obtained for the upper crust from focal mechanisms of numerous earthquakes (M ≥ 1) in the northern and axial parts of the Tajik Depression (the Garm area, Tajikistan). It is shown that, in the majority of cases, a close interrelation exists between tectonic structures and the STS type. Changes in the STS characteristics in various areas of the depression admit a reasonable geological interpretation. Based on geological, seismological, and geodetic data, a unified scheme of deformation of layered rocks of the Tajik Depression is presented. The main factor controlling the deformation process is the extrusion of the rocks in the axial part of the depression in the NNW and SSE directions (with the formation of imbricate thrusts) and in the WSW direction. The latter case is characterized by left-lateral motions in fault zones in the south of the depression (including the Darvaz fault) and by right-lateral motions in northern zones (the Peter the First Range) located from seismological data. In our opinion, such expulsion is caused mainly by an increase of the volume of layered rocks in the Tajik Depression, apparently due to deep fluids penetrating into these rocks and supplying additional mineral material. However, it is also possible that the region is influenced, to an extent, by the general subhorizontal N-S compression associated with the convergence of the Indian and Eurasian lithospheric plates in accordance with the concept of plate tectonics.     

Tsunami Measurements in Bays of Shikotan Island

Bottom pressure gauges deployed in bays of Shikotan Island (South Kuril Islands) recently recorded two tsunamis: the Simushir (Kuril Islands) tsunami of January 13, 2007 generated by a local earthquake with magnitude M _w = 8.1 and the Peruvian tsunami of August 15, 2007 generated by a distant earthquake, M _w = 8.0. The records enabled us to investigate the properties of these two tsunamis and to estimate the effect of the regional and nearshore topography on arriving tsunami waves. Eigen periods and spatial structure of resonant oscillations in particular bays were examined based on results of numerical modeling. Significant amplification of the fundamental (Helmholtz) resonant modes in Malokurilskaya Bay (19 min) and in Krabovaya Inlet (29 min) and some secondary modes was caused by the Simushir tsunami. The considerably different geometry and bottom topography of these bays, located on the inner coast of the island, determine the differences in their eigen periods; the only mutual peak, which was found in both basins, had a period of 5 min and was probably related to the source features. The Peruvian tsunami was clearly recorded by the bottom pressure gauge in Tserkovnaya Bay on the outer (oceanic) coast of the island. Three dominant periods in the tsunami spectrum at this bay were 60, 30 and 19 min; the latter period was found to be related to the fundamental mode of the bay, while the other two periods appear to be associated with the shelf resonant amplification of tsunami waves arriving in the region of the South Kuril Islands. The prevalence of low-frequency components in the observed tsunami spectrum is probably associated with the large extension of the initial source area and faster decay of short period waves during the long trans-oceanic tsunami propagation.