Dynamic processes in the system of interacting geospheres at the Earth’s crust-atmosphere boundary

Results of various instrumental observations of geodynamic processes in the Earth’s crust and geophysical fields at the crust-atmosphere boundary in the Oka area of the Nelidovo-Ryazan tectonic structure and adjacent fractures and in the zone of the Gornyi Altai earthquake of September 27, 2003, are presented. The correlations between the geophysical fields are determined from the results of processing and analysis of microseismic vibrations, the emanation field of natural radon, and variations in the electric field in ground and the magnetic field in the surface atmospheric layer. Tidal deformations of the crust were considered as external effects enhancing the interactions between the geospheres. It is noted that tectonic faults determining the block structure of the crust are recognizable as anomalous variations in the geophysical fields and their high cross-correlation.     

Seismicity and seismotectonic deformations of the crust in the Southern Baikal basin

This paper addresses the seismicity of the Southern Baikal basin, where the M _w = 6.0 earthquake of 1999 was the strongest over the period of instrumental observations in this region. Focal mechanisms of background earthquakes and aftershocks are analyzed in relation to faults mapped on flanks of and within the basin. Based on a supplemented catalog of focal mechanisms, the value and direction of seismotectonic strain are evaluated. The results show that the territory to the west of the transverse Angara fault (the Mishikhinskaya depression) experiences deformation of pure extension, while the E-W basin segment west of the fault is subjected to deformation of extension with shear (the transtension regime). The crustal deformation directions as determined from GPS measurements and seismological observations are found to agree well. The average seismotectonic strain rate of the crust amounts to 2.95 × 10^?9 yr^?1, which is about an order of magnitude smaller than the value obtained from geodetic observations.     

Stress-strain state of the lithosphere in the southern Baikal region and northern Mongolia from data on seismic moments of earthquakes

Investigation and understanding of the present-day geodynamic situation are of key importance for the elucidation of the laws and evolution of the seismic process in a seismically active region. In this work, seismic moments of nearly 26000 earthquakes with K _p ≥ 7 (M _LH ≥ 2) that occurred in the southern Baikal region and northern Mongolia (SBNM) (48°–54°N, 96°–108°E) from 1968 through 1994 are determined from amplitudes and periods of maximum displacements in transverse body waves. The resulting set of seismic moments is used for spatial-temporal analysis of the stress-strain state of the SBNM lithosphere. The stress fields of the Baikal rift and the India-Asia collision zone are supposed to interact in the region studied. Since the seismic moment of a tectonic earthquake depends on the type of motion in the source, seismic moments and focal mechanisms of earthquakes belonging to four long-term aftershock and swarm clusters of shocks in the Baikal region were used to “calibrate” average seismic moments in accordance with the source faulting type. The study showed that the stress-strain state of the SBNM lithosphere is spatially inhomogeneous and nonstationary. A space-time discrepancy is observed in the formation of faulting types in sources of weak (K _p = 7 and 8) and stronger (K _p ≥ 9) earthquakes. This discrepancy is interpreted in terms of rock fracture at various hierarchical levels of ruptures on differently oriented general, regional, and local faults. A gradual increase and an abrupt, nearly pulsed, decrease in the vertical component of the stress field S _v is a characteristic feature of time variations. The zones where the stress S _v prevails are localized at “singular points” of the lithosphere. Shocks of various energy classes in these zones are dominated by the normal-fault slip mechanism. For earthquakes with K _p = 9, the source faulting changes with depth from the strike-slip type to the normal-strike-slip and normal types, suggesting an increase in S _v . On the whole, the results of this study are well consistent with the synergism of open unstable dissipative systems and are usable for interpreting the main observable variations in the stress-strain state of the lithosphere in terms of spatiotemporal variations in the vertical component of the stress field S _v . This suggests the influence of rifting on the present-day geodynamic processes in the SBNM lithosphere.     

Frequency dependence of the scattering pulse broadening for the Crab pulsar

We measured the frequency dependence of the pulsar pulse broadening by scattering over a wide frequency range, from 40 to 2228 MHz, based on direct measurements of this parameter using giant pulses from the pulsar PSR B0531+21 in the Crab Nebula. Our measurements were carried out at the following seven frequencies: 40, 60, and 111 MHz at the Pushchino Radio Astronomy Observatory (Astrospace Center, Lebedev Physical Institute, Russian Academy of Sciences), 406 MHz at the Medicina Observatory (Instituto di Radioastronomia, Italy), and 594, 1430, and 2228 MHz at the Kalyazin Radio Astronomy Observatory (Astrospace Center, Lebedev Physical Institute, Russian Academy of Sciences). The measured frequency dependence of the pulse broadening by scattering τ_SC (υ) ? υ^γ, where γ=?3.8±0.2, agrees with a model Gaussian distribution of interstellar inhomogeneities (γ=?4) but falls outside the error limits of correspondence to a Kolmogorov model spectrum of inhomogeneities (γ=?4.4).     

测定一块岩石成岩压力的可能性

用一种超低弹性模量(约为0.01MPa)且具有光弹性的软材料铸模的自重卸荷实验证明了固体材料对它的固化压力具有“记忆”的属性。根据成岩地质体在开挖条件下实测位移场特征和用具有“记忆”性能的相似材料所做的开挖模拟实验结果分析,岩石很可能也具有这种属性。这就为测定岩石成岩压力的可能性提供了重要的理论依据。     

A recent history of metal accumulation in the sediments of the Thames Estuary, United Kingdom

Sediment cores were collected from the Tilbury Tidal Basin in the Thames Estuary to determine the depositional history of metals in the estuary. Profiles of metals in sediments deposited in the lower Thames Estuary show a 30–50% decrease in concentration for Ag, Cd, Cu, Pb, and Zn, and a 70% decrease for Hg in recent decades. Historic depth soundings data showed the decreases in metal concentrations occurred between 1944 and 1966. The decline in sediment metal concentrations has been attributed to reduced inputs to the estuary, following updating of the major sewage treatment works in 1959 and 1963. This is indicated by the through-core distribution of Mn which implies that prior to 1960 the sediments were deposited in anoxic conditions, which subsequently improved. An increase in Mn concentrations observed in one of the cores has been attributed to increases in the dissolved oxygen of the estuarine waters resulting from the increased efficiency of the sewage treatment works.     

震旦纪地层黄铁矿硫同位素组成时－空变化特征及扬子地块与晚元古超大陆关系的论证

 扬子地区早震旦世时期沉积岩黄铁矿具有重的硫同位素组成,其δ¹⁴S值从早震旦世椿木组地层的24‰左右逐渐变得更正。在早震旦世扬子地区广泛沉积碳酸锰矿和黑色页岩的民乐组时期达到极正值+60‰,然后又降低至+16‰-+20‰。上述硫同位素组成的时-空变化特征支持了扬子地块属晚元古Rodinia超大陆的一个组成部分的假设。从晚震旦世早期陡山沱组底部开始,沉积岩中黄铁矿硫同位素的δ¹⁴SS出现负值,并继续降低至-27‰以下。早震旦世晚期-晚震旦世早期沉积岩中硫同位素组成特征反映了沉积盆地古海洋环境的剧烈变化,它与大约7亿年时Rodinia超大陆的解体以及扬子地块与其它大陆分离的地质推测相吻合。     

Long-term improvements in water quality due to sewage abatement in the lower Hudson River

Long-trend trends in dissolved oxygen (DO) and total coliform bacteria concentrations are used to evaluate the impact of almost 60 yr of sewage abatement and treatment in the lower Hudson River near New York City. Although some water pollution control plants have been in operation in the region since the 1930s, the most significant abatement of untreated sewage in the lower Hudson River has occurred since the late 1970s, when most of the existing plants were upgraded to secondary treatment, and additional plants were constructed. From at least 1922 through the early 1960s, average summer DO percent saturation varied between 35% and 50% in surface waters and 25% and 40% in bottom waters. Beginning in the late 1970s, DO concentrations generally increased through the 1980s and especially into the 1990s, coinciding with the upgrading of the 7.4 m³ s^?1 (170 million gallons per day, mgd) North River plant to secondary treatment in the spring of 1991. Average summer percent saturation in the early 1990s exceeded 80% in surface waters and 60% in bottom waters. In addition, summer DO minima have increased from less than 1.5 mg 1^?1 in the early 1970s to greater than 3.0 mg 1^?1 in the 1990s, and the duration of hypoxia during summer months has been reduced. Total coliforms also display strong declining trends from the 1970s into the 1990s, with declines attributed to plant upgrades, construction of two New York City plants (North River and Red Hook) in the mid 1980s, and improved operation of the sewer system.     

Acceleration of multiply charged ions of the anomalous cosmic-ray component at the heliosphere boundary

The formation of the energy spectra of heavy ions at the front of a parallel shock is considered taking into account ionization and recombination during the acceleration. An analytic solution for ions with three possible charge states is obtained and applied to the acceleration of the anomalous cosmic-ray component at the boundary of the heliosphere. In addition, a more general numerical model for such acceleration at a spherical shock front is developed and used to obtain the energy dependence of the mean charges for C, N, O, Ne, Si, S, Ar, and Fe ions. The model implies that highly excited ions begin to dominate over ions with low charges at energies above 1 MeV/nucleon, in agreement with observational data.