The 2008 Kultuk earthquake with M w = 6.3 in the south of Baikal: Spatial-temporal analysis of seismic activation

The results of investigating the data of stationary and field observations in the epicentral zone of the Kultuk earthquake of August 27, 2008 with M _w = 6.3 localized south of Baikal are presented. The seismic activation amounting to 1790 aftershocks with K _p ?? 4 (M _w ?? 0.9) affected a part of the general fault bounding the southwestern coast of the lake and shallower intrabasin structures. It was established through the cluster analysis that the main shock was located at the periphery of the cloud of the concentrated seismicity component, and three main clusters reflecting a complex character of rupture in the earthquake source were identified in the zone of aftershocks. Owing to a high accuracy of aftershock hypocenters determinations (ERZ ?? 1.2 km), the local character of the seismisity-generating zones was revealed. Based on the method of mapping seismic regime parameters, it was established that zones of reduced fractionality are recognizable in the central part of the source area; in this case, the entire periphery, except for the southeastern direction (where the main shock epicenter is located), is characterized by a high fractionality, which also points to the complex character of the rupture in the source. On the whole, the aftershock sequence under consideration showed the activation of the southwestern flank of the Southern Baikal region, which remained passive for more than one century, and demonstrated destructive features of the Earth??s crust.     

Geodynamic aspects of the development of offshore oil and gas deposits: Case study of Barents region

Geodynamic aspects of the development of offshore deposits in the Russian sector of Barents region are considered. The main technogenic geohazards at oil hydrocarbon extraction are shown to be land subsidence and earthquakes. A concept of studying geodynamic manifestations is substantiated. This concept is based on the evolution of oil-and-gas-producing enterprise with appropriate portion of geological environment, regarded as a complex open natural-engineering system. The geodynamic situation at the Shtokman gas-condensate field was simulated using a mathematical model. The model showed some regularities in the deformation of the fluid-bearing massif because of gas extraction, including the up to 30% volumetric compaction of the production strata, resulting in a regression deflection (subsidence) of seabed and considerable subhorizontal deformations and displacements of bottom rock beds. The specific features of gas pipeline laying from the Shtokman field through Murmansk province are discussed, and the structure of geodynamic monitoring is proposed. Substantiation is given to the need to carry out special geodynamic studies in the Barents region with the aim to ensure operation geosafety and stability of structures of oil-and-gas facilities and pipeline transportation of hydrocarbons materials.     

预破裂中声波信号参数特性

通过对岩石样品进行变形及破坏试验，研究断裂形成过程中的声发射记录（ＡＥ），以找到能解释地震前兆现象的方法．另外，对试验过程中获得的大量数据及资料进行了数理统计处理．     

Vegetation influences on water yields from grassland and shrubland ecosystems in the Chihuahuan Desert

This study examines runoff generated under simulated rainfall on Summerford bajada in the Jornada Basin, New Mexico, USA. Forty‐five simulation experiments were conducted on 1 m² and 2 m² runoff plots on grassland, degraded grassland, shrub and intershrub environments located in grassland and shrubland communities. Average hydrographs generated for each environment show that runoff originates earlier on the vegetated plots than on the unvegetated plots. This early generation of runoff is attributed to soil infiltration rates being overwhelmed by the rapid concentration of water at the base of plants by stemflow. Hydrographs from the degraded grassland and intershrub plots rise continuously throughout the 30 min simulation events indicating that these plots do not achieve equilibrium runoff. This continuously rising form is attributed to the progressive development of raindrop‐induced surface seals. Most grassland and shrub plots level out after the initial early rise indicating equilibrium runoff is achieved. Some shrub plots, however, display a decline in discharge after the early rise. The delayed infiltration of water into macropores beneath shrubs with vegetation in their understories is proposed to explain this declining form. Water yields predicted at the community level indicate that the shrubland sheds 150 per cent more water for a given storm event than the grassland. Copyright © 2002 John Wiley & Sons, Ltd.     

Yasny lode-placer cluster: Geological and structural features and gold potential

The geological and structural features and gold potential of the Yasny lode-placer cluster in Amur province have been investigated. The lode-placer cluster is an intrusive domal uplift elongated in the nearmeridional direction and surrounded by Neogene loose sediments. The cluster comprises placers that yielded 15 t gold mined from there and small occurrences of gold-quartz and gold-base-metal lodes. Association of native gold with cinnabar in the Yasny Creek placer allows us to forecast a new source of gold-mercury mineralization in the basin of this creek, which could be compared with the Kyuchyus deposit in Yakutia. Gold nuggets 79 kg in total weight were mined from Gar-2 River placer. They are comparable in weight and association with quartz to the world’s largest Holtermann Plate nugget from Australia. Gold-quartz lodes have been forecasted in the basin of the Gar-2 Creek.     

The chemical composition of solar-type stars in comparison with that of the Sun

The question whether the solar chemical composition is typical for solar-type stars is analysed by comparing the Sun with different stellar samples, including a sample of stars with very similar parameters, solar twins. Although typical in terms of overall metallicity for stars of solar age and galactic orbit, the solar atmosphere is found to have abundances, as compared with solar twins, that indicate that its gas has once been affected by dust formation and dust separation. It is concluded that this may be related to the formation of the solar planetary system and its special properties.     

The submicroscopic structures of mesozoic-cenozoic Fe-Mn stromatolites

The results of the study of submicroscopic structures of oceanic oxide ores are described. The objects of study were Co-bearing Fe-Mn crusts from the Magellan Seamounts and Fe-Mn nodules from the Clarion-Clipperton province. The evolution of structural elements is traced in the crust section from the Lower Campanian-Maastrichtian to Pliocene-Quaternary layers. It was found that growing nodules actively entrap hosting sediments into the layered cover. The entrapment mechanism of sediments by nodules was revealed.     

Chaotic Dynamics of Satellite Systems

We consider the problem of calculating the Lyapunov time (the characteristic time of predictable dynamics) of chaotic motion in the vicinity of separatrices of orbital resonances in satellite systems. The primary objects of study are the chaotic regimes that have occurred in the history of the orbital dynamics of the second and fifth Uranian satellites (Umbriel and Miranda) and the first and third Saturnian satellites (Mimas and Tethys). We study the dynamics in the vicinity of separatrices of the resonance multiplets corresponding to the 3 : 1 commensurability of mean motions of Miranda and Umbriel and the multiplets corresponding to the 2 : 1 commensurability of mean motions of Mimas and Tethys. These chaotic regimes have most probably contributed much to the long-term orbital evolution of the two satellite systems. The equations of motion have been numerically integrated to estimate the Lyapunov time in models corresponding to various epochs of the system evolution. Analytical estimates of the Lyapunov time have been obtained by a method (Shevchenko, 2002) based on the separatrix map theory. The analytical estimates have been compared to estimates obtained by direct numerical integration.__________Translated from Astronomicheskii Vestnik, Vol. 39, No. 4, 2005, pp. 364–374.Original Russian Text Copyright © 2005 by Mel’nikov, Shevchenko.