Peculiarities of Dynamic Slip Nucleation in a Thin Granular Layer

Izvestiya, Physics of the Solid Earth - Abstract—Granular media determine the dynamics of many natural systems including faults in the Earth’s crust. The paper addresses the laboratory...     

State of stress in the northern Tabas block, east-central Iran, as inferred from focal mechanisms of the 1978 Tabas earthquake sequence

In this paper, the state of stress in the northern Tabas block in east-central Iran is analyzed based on the systematic inversion of aftershock focal mechanisms from the 1978.09.16 Tabas earthquake, to characterise the stress regime that controls most earthquakes in this area. Here, stress inversions of double-couple focal mechanisms of earthquakes recorded during the 30 days following the main shock have been carried out. The calculated average stress regime indicates dominant major 226° to 237° trending compression for the Tabas region. The dominating regime in east-central Iran is thrusting with a minimum stress axis, σ ₃, close to vertical. The reconstruction of the main seismotectonic stress in east-central Iran with a NE-SW compression is consistent with independent information of the active plate convergence related to Arabia-Eurasia convergence. Most earthquakes in the mentioned area occur near or around concealed Quaternary thrust faults with their activity being controlled by the NE-SW compression. Where ?, the ratio of principal stress differences, is 0.5, a small difference between σ ₂; σ ₃ and σ ₁ and small amounts of deviatoric stress is indicated. Therefore, for small deviatoric horizontal σ ₁ it is not possible to increase and reactivate small sections of basement thrust faults and create secondary basement aftershocks. Reconstructed stress regimes in this study for sedimentary cover (237) and basement (226) of Tabas are similar. Therefore, it seems that the basement and cover were coupled together, possibly along the 2–4 km of upper Precambrian low-grade metamorphic rocks. Then these segments of the fold-and-thrust belt were involved in similar seismic activity under a similar stress regime.     

The interpretation of body trace metal concentrations in neogastropods from Hong Kong.

Three species of neogastropods, i.e., Thais clavigera, Thais luteostoma and Morula musiva, were collected from 12 sites in the coastal waters of Hong Kong, including clean and known metal-enriched ones. Accordingly, body trace metal concentrations varied greatly. Copper and zinc body concentrations compared poorly with those of accepted biomonitors and presumed metal contamination profiles. Much is known about the feeding ecology of neogastropods on local shores and where direct observational data were not available, their diets could, nevertheless, be estimated reliably. Accumulated metal concentrations can be interpreted with regard to dietary history. T. luteostoma, for example, had body copper concentrations of 51.8 microg g(-1) on an exposed shore and a diet of mainly barnacles. In contrast, on a sheltered shore (but only some 250 m distant) where the diet consisted mainly of oysters, body copper concentrations were approximately 15 times greater at 833 microg g(-1). Similar results were obtained for T. clavigera. The results of this analysis suggest that neogastropods can play a significant role in trace metal trophic transfer studies, especially as their representatives are intertidally and subtidally ubiquitous and can be spatially separated into tropical specialists and temperate generalists.     

Biosorption of Rare-Earth Elements and Yttrium by Heterotrophic Bacteria in an Aqueous Environment

This paper reports the results of the experimental determination of the coefficient of sorption of rare-earth elements and yttrium (REY) under conditions of acidic pH using several strains of heterotrophic bacteria (Microbacterium sp., Curtobacterium sp., Bacillus subtilis, Pseudomonas putida, and Bacillus pumilis) that are widespread in natural and technogenic waters of the Far East (Russia). Insignificant fractionation between heavy and light rare-earth elements, negative cerium and dysprosium anomalies, and a positive europium anomaly were revealed. The selectivity of REY biosorption by gram-positive and gram-negative bacteria, as well as inertia of the biosorption process under more acidic conditions of the medium, were shown.     

Determination of the optimum period for ciliated protozoa colonizing of an artificial substrate in a tropical aquatic ecosystem

The optimum period for ciliated protozoa colonizing of an artificial substrate, the polyurethane foams have been assessed in a tropical aquatic ecosystem, the Ekozoa stream of the Mfoundi River Basin in Yaounde (Cameroon). 5?days were calculated as the highest period for the biological indicators of pollution to optimally colonize the artificial substrate. This time interval is the same for all the sampling stations assessed from upstream to downstream and the various microhabitats along the water course. The statistical method applied is that of the completely randomized blocks. The colonization of the substrate increases from the first day to the fifth day, before decreasing to the tenth day. The statistical analysis of variance between the maximum day and the other sampling period was significant at 5?% while the calculation of the value between different points of the same station was not significant. The average number of ciliated protozoan ranges from 20 to 23, from upstream to downstream.     

Formalization of assessing radioactive waste burial site seismic regime parameters from seismological and geological data

A model is proposed that shows the relation of the block structure of the crust and earthquake sources (Sadovskii, 1979; Rodionov, 1979, 1984, 1994; Bugaev, 1999, 2011, 2014, 2015). The model can formalize how to assess the prediction of seismic regime parameters depending on the elastic limit and conditions and rate of deformation of the Earth’s crust. The spent nuclear fuel repository site in Olkiluoto (Finland) and a site in the area of the Krasnoyarsk Mining and Chemical Combine are considered as examples. It is demonstrated that the parameters of the prediction graphs limit the location of the points of magnitude repeatability graphs calculated for a site based on samples of earthquakes in the area according to different authors. This makes it possible to recommend predictive assessment of seismic regime parameters for stability monitoring of the seismic regime and safety analysis of a geological environment’s insulation properties for waste sites from the results of seismological monitoring and high-precision observations of modern movements of the Earth’s crust.     

Soil bentonite wall protects foundation from thrust faulting: analyses and experiment

When seismic thrust faults emerge on the ground surface,they are particularly damaging to buildings,bridges and lifelines that lie on the rupture path.To protect a structure founded on a rigid raft,a thick diaphragm-type soil bentonite wall(SBW) is installed in front of and near the foundation,at sufficient depth to intercept the propagating fault rupture.Extensive numerical analyses,verified against reduced–scale(1 g) split box physical model tests,reveal that such a wall,thanks to its high deformability and low shear resistance,"absorbs" the compressive thrust of the fault and forces the rupture to deviate upwards along its length.As a consequence,the foundation is left essentially intact.The effectiveness of SBW is demonstrated to depend on the exact location of the emerging fault and the magnitude of the fault offset.When the latter is large,the unprotected foundation experiences intolerable rigid-body rotation even if the foundation structural distress is not substantial.     

An observational constraint on the existence of proto-superclusters at z =3.3

Observations have been conducted using the Ooty Radio Telescope in order to place constraints on the evolutionary scenario leading to the formation of the present day superclusters. The experiment attempted to detect 21 cm emission from massive neutral hydrogen condensates at a redshift ofz = 3.3. In an Einstein de-Sitter universe with baryon density Ω = 0.05, about ten condensates were expected in the volume surveyed if superclusters, having H I masses ≃5 × 10₁₅ M _⊙, were the first objects to separate out of the Hubble expansion. The sensitivity of our experiment rules out the existence of these condensates atz = 3.3 unless their lifetimes are less than one-tenth the dispersion in their epoch of formation or the proto-superclusters subtend angles greater than 6 arcmin. The result indicates that superclusters form at z > 3.3 if indeed they were the first objects to condense out of the Hubble flow. An erratum to this article is available at .