The global solution of the problem of the critical inclination

The publication of the solution of the Ideal Resonance Problem (Garfinkelet al., 1971) has opened the way for a complete first-orderglobal theory of the motion of an artificial satellite, valid for all inclinations. Previous attempts at such a theory have been only partially successful. With the potential function restricted to $$V = - 1/r + J_2 P_2 (\sin \theta )/r^3 + J_4 P_4 (\sin \theta )/r^5 ,$$ the paper constructs aglobal solution of the first order in √J ₂ for the Delaunay variablesG, g, h, l and for the coordinatesr, θ, and ?. As a check, it is shown that this solution includes asymptotically theclassical limit with the critical divisor 5 cos² i?1. The solution is subject to thenormality condition $$eG^2 /(1 + \frac{{45}}{4}e^2 ) \geqslant O\left[ {\left| {\frac{1}{5}(J_2 + J_4 /J_2 )} \right|^{1/4} } \right],$$ which bounds the eccentricitye away from zero in deep resonance. A historical section orients this work with respect to the contributions of Hori (1960), Izsak (1962), and Jupp (1968).     

Propagating PZ 90 to WGS 84 Transformation Parameters

The 29^th Research Institute recently published its latest transformation parameters for WGS and PZ 90. Because these tranformation parameter estimates were derived from stations located within Russia, variance-covariance propagation was carried out to study the benefits of a better global distribution of stations. An example that includes two stations in North America is presented. The transformation improves significantly. ? 1999 John Wiley & Sons, Inc.     

Neotectonics and recent uplift at Kamchatka and Aleutian arc junction, Kamchatka Cape area, NE Russia

The tectonic position of the Kamchatka Cape Peninsula at the junction of the active Kuril–Kamchatka and Aleutian arcs exposes the coastline of the peninsula to strong neotectonic activities. Fracture zones have variable influence on uplift of the Kamchatka Cape Peninsula. Relevant morphologic indicators of neotectonic activity are multilevel, highly uplifted marine terraces and terraces displaced along active faults. Recent uplift rates of coastal sediments are determined by remote sensing via ASTER and SRTM DEM combined with optically stimulated luminescence dating (OSL). On the Kamchatka Cape Peninsula, terraces from the same generation are mapped at different elevations by remote sensing methods. After defining different areas of uplifted terraces, four neotectonic blocks are identified. According to apatite fission track data, the mean differential exhumation rates range from 0.2 to 1.2 mm year^?1 across the blocks since Late Miocene. The OSL data presented point to significant higher uplift rates of up to 3 ± 0.5 and 4.3 ± 1 mm year^?1, which indicates an acceleration of the vertical movement along the coast of Kamchatka Cape Peninsula in Upper Pleistocene and Holocene times.     

Hyperspectral core logging for fire reconstruction studies

Lacustrine sediments contain a wide range of proxies that enable paleoenvironmental reconstructions. For instance, charcoal can be used to document past fire regime changes. In order to analyse high-temporal- and spatial-resolution records, however, it is necessary to develop fast, low-cost and high-stratigraphic-resolution methods. We developed a new paleo-fire proxy by studying a lacustrine core from the Esterel Massif, SE France, an area affected by two recent fire events, in AD 1987 and 2003. For this purpose, we searched for charcoal deposited and preserved in the lake sediments by combining a number of complementary methods, including: classic macrocharcoal tallying, scanning spectrophotometry, scanning hyperspectral imaging and high pressure liquid chromatography analyses. Macrocharcoal quantification is efficient, but time-consuming, and only provides intermediate-resolution data (cm scale). Spectrophotometry, used classically to quantify colour, is very fast, provides high-resolution data (4 mm) and is non-destructive (core preservation). Hyperspectral data have the same advantages as spectrophotometry, but offer higher spatial resolution (64-µm pixel size) and higher spectral resolution (6 nm) for core logging applications. The main result of this research is based on hyperspectral analysis at very high stratigraphic resolution using the I-band index. This index usually measures reflectance values at [660, 670 nm] corresponding to the trough in red reflectance produced by Chlorophyll a and its diagenetic products. This [660, 670 nm] reflectance trough, however, is also affected by the presence of altered organic matter and decreases with altered organic matter such as charcoal particles. Charcoal effect on the reflectance of Chlorophyll a and its diagenetic products is identified on first derivative spectra by a characteristic pattern around 675 nm, which is also in agreement with the Chlorophyll a concentrations measured by high-pressure liquid chromatography and charcoal particles. The I-band index is hence suitable for detecting burned organic matter, by quantifying the dilution of the chlorophyll signal by the charcoal signal. Thus, this adaptation of the I-band index can be applied in fire reconstruction studies.     

Self‐consistent subduction initiation induced by mantle flow

Mantle circulation in planets with strongly temperature‐dependent viscosity results in stagnant‐lid convection. It is fundamental to understand how this stagnant‐lid regime can change into a plate‐like convection regime as on the present‐day Earth. Here, we use 2D numerical models to study subduction initiation from an initial stagnant lid with laboratory‐consistent parameters and without pre‐existing weak zones or kinematic boundary conditions. Our results show that subduction can be initiated dynamically as a result of a thermal localization instability. The lithosphere may deform in a stagnant‐lid mode, an un‐necking mode, a symmetric‐subduction mode or an asymmetric‐subduction mode. The asymmetric‐subduction mode occurs only for relatively large friction angles and moderate thermal ages, and the presence of heterogeneities increases the parameter space of this mode. The limited parameter space might explain why only the present‐day Earth has plate tectonics, and suggests that the initiation of plate tectonics is more difficult than previously anticipated.     

Water retention effects on elastic properties of Opalinus shale

Shales play an important role in many engineering applications such as nuclear waste, CO₂ storage and oil or gas production. Shales are often utilized as an impermeable seal or an unconventional reservoir. For both situations, shales are often studied using seismic waves. Elastic properties of shales strongly depend on their hydration, which can lead to substantial structural changes. Thus, in order to explore shaly formations with seismic methods, it is necessary to understand the dependency of shale elastic properties on variations in hydration. In this work, we investigate structural changes in Opalinus shale at different hydration states using laboratory measurements and X-ray micro-computed tomography. We show that the shale swells with hydration and shrinks with drying with no visible damage. The pore space of the shale deforms, exhibiting a reduction in the total porosity with drying and an increase in the total porosity with hydration. We study the elastic properties of the shale at different hydration states using ultrasonic velocities measurements. The elastic moduli of the shale show substantial changes with variations in hydration, which cannot be explained with a single driving mechanism. We suggest that changes of the elastic moduli with variations in hydration are driven by multiple competing factors: (1) variations in total porosity, (2) substitution of pore-filling fluid, (3) change in stiffness of contacts between clay particles and (4) chemical hardening/softening of clay particles. We qualitatively and quantitatively analyse and discuss the influence of each of these factors on the elastic moduli. We conclude that depending on the microstructure and composition of a particular shale, some of the factors dominate over the others, resulting in different dependencies of the elastic moduli on hydration.     

Mercury pollution in sediments,benthic organisms and inshore fishes of Haifa Bay,Israel

Total mercury concentrations were determined in surficial sediments, eleven species of benthic organisms and six species of fish from Haifa Bay, Israel. The results show that essentially all of the shallow water zone of the Bay receives anthropogenic mercury. A mercury-cell chlor-alkali plant was identified as the source of pollution. Surficial sediments in the vicinity of the plant, containing up to 0·99 μg Hg/g dry weight, were up to 157 times enriched in mercury relative to an unpolluted area. Mercury levels in the benthic organisms reflected the levels in the sediments. Maximal concentrations reaching 38·7 and 18·2 μg Hg/g dry weight were found in the carnivorous gastropod molluscs Arcularia circumcinta and Arcularia gibbosula, respectively. In all fish species, specimens caught in Haifa Bay had higher mercury concentrations in the muscle tissue than specimens caught south of the Bay. A maximal value of 1·66 μg Hg/g wet weight was recorded in Diplodus sargus.