Time-dependent stress change during failure of rocks

The energy balance of a solid subject to fracture has been explored using heat and mass transfer equations with regard to the volumetric and superficial components. In the suggested model, brittle fracture of a cracked solid considered as a heterogeneous two-phase medium is described by an equation analogous to the Griffith’s criterion for propagation of a single crack. The derived equation is used, together with estimates of relative change in specific interface area, to study the respective change of free strain energy and pressure in rocks associated with failure.     

Inversion of arrival-times in a region of dilatancy anisotropy

Shear-wave splitting has been identified in many three-component seismograms from two separate field experiments on a section of the North Anatolian Fault in North-West Turkey. These observations are consistent with shear-wave propagation through a zone of extensive-dilitancy anisotropy. A preliminary attempt has been made to confirm this interpretation by simultaneously inverting suites of arrival-times for hypocentral locations and for parameters describing an anisotropic halfspace. Although the inversion procedure is not globally convergent, it is possible to recognize the true solution by systematically varying the initial conditions. Applied to selected data sets, the inversion defines several anisotropic models that fit the data significantly better than a simple isotropic model, and display the anisotropy required by the shear-wave splitting. However, most of these anisotropic models are not superior when they are used to individually locate events in a much larger data set. However, for each experiment, there is a single model that produces clearly superior locations for the larger data sets than those of other anisotropic or simple isotropic models. Both models display similar velocity variations which are characteristic of propagation through distributions of biplanar cracks displaying orthorhombic symmetry. The principal axes of the two models are oriented in similar directions and are within 20° of the principal axis of regional stress derived from fault-plane solutions. The solutions indicate low velocities close to the tensional axis, as would be expected in extensive-dilatancy anisotropy.     

Space-time characteristics of a fracture region determined from long-term anomalies of the radon concentration

The paper proposes a method for studying long-term anomalies of the radon concentration that are produced by an impulse generated in a fracture source over a finite time interval. Using this method, experimental data are interpreted numerically in order to determine the space-time characteristics of the fracture region and parameters of fluid migration.     

Neutron capture on Gd and Sm in the Luna 16, G-2 soil

The Gd and Sm isotopic compositions have been measured in the Luna 16, G-2 soil. This sample has the largest low energy neutron fluence ψ = 5.9 × 10¹⁶n/cm² (E < 0.18eV) yet observed in a lunar sample. The ratio of the number of neutrons captured per atom by¹⁴⁹Sm to¹⁵⁷Gd is 0.76 which is distinct from the value of 0.86 observed at the Apollo 11, 12 and 14 sites. This indicates a softer neutron energy spectrum at the Sea of Plenty.     

Apollo 16 neutron stratigraphy

The Apollo 16 soils have the largest low energy neutron fluences (up to 10¹⁷ n/cm², E < 0.18eV) yet observed in lunar samples. Variations in the isotopic ratios ¹⁵⁸Gd/¹⁵⁷Gd and ¹⁵⁰Sm/¹⁴⁹Sm (up to 1.9% and 2.0% respectively) indicate that the low energy neutron fluence in the Apollo 16 drill stem increases with depth throughout the section sampled. Such a variation implies that accretion has been the dominant regolith “gardening” process at this location. The data may be fit by a model of continuous accretion of pre-irradiated material at a rate of ～70 g/(cm² · 10⁸yr) or by models involving as few as two slabs of material in which the first slab could have been deposited as long as 10⁹ yr ago.The ratio of the number of neutrons captured per atom by Sm to the number captured per atom by Gd is lower than in previously measured lunar samples, which implies a lower energy neutron spectrum at this site. The variation of this ratio with chemical composition is qualitatively similar to that predicted by Lingenfelter, Canfield and Hampel.Variations are observed in the ratio ¹⁵²Gd/¹⁶⁰Gd which are fluence correlated and probably result from neutron capture by¹⁵¹Eu.     

A CME mass distribution derived from SOLWIND coronagraph observations

Using estimates of the masses of nearly 1000 CMEs observed by SOLWIND from Howardet al. (1985), we re-plot the numbers of CMEs as a function of CME mass on a log-linear plot. The plot is significant in that it shows a linear trend over more than a decade of CME masses. The plot indicates a simple form for the distribution of the CME masses and allows an easy determination of the total mass ejected into the solar wind in the form of CMEs. We find that approximately 16% of the solar wind at solar maximum can be comprised of CME mass. There is no indication that the numbers of low-mass CMEs increase in number above the trend set by the more massive ones. Specifically, there is no increase in the numbers of small CMEs such that the whole of the solar wind can be comprised of them.     

Convolute laminations — a theoretical analysis: example of a Pennsylvanian sandstone

Data from an outcropping laminated interval were collected and analyzed to test the applicability of a theoretical model describing instability of layered systems. Rayleigh—Taylor wave perturbations result at the interface between fluids of contrasting density, viscosity, and thickness. In the special case where reverse density and viscosity interlaminations are developed, the deformation response produces a single wave with predictable amplitudes, wavelengths, and amplification rates.Physical measurements from both the outcropping section and modern sediments suggest the usefulness of the model for the interpretation of convolute laminations. Internal characteristics of the stratigraphic interval, and the developmental sequence of convoluted beds, are used to document the developmental history of these structures.     

The impact of the nitrogen carryover effect on economic activity and the environment

 The economic and environmental consequences of soil nitrogen tests can have significant impacts on agricultural production. Some of these are explored here. The pre-side-dress soil N-test is evaluated for a hypothetical farmer growing corn at the ARS Sustainable Agriculture Demonstration Farm site in southern Maryland. For a farmer not currently using a soil N-test, adoption of this technology can lead to the enhancement of net farm income and the reduction in nitrogen loss to the environment. This will transpire only if the farmer is currently underestimating nitrogen carryover by more than 25% or applying nitrogen fertilizer based solely on an expected plateau-yield goal. Received: 13 February 1997 · Accepted: 13 May 1997     

Climatic and environmental characteristics of Moscow megalopolis according to the data of the Moscow State University Meteorological Observatory over 60 years

Analyzed are the results of meteorological and environmental measurements performed over the 60-year period (1954–2013) at the Meteorological Observatory of Lomonosov Moscow State University. The significant positive temperature trend (0.04°C/year for 1954–2013) was obtained; it increased up to 0.07°C/year in 1976–2012. Considered are the features of seasonal variations of different atmospheric characteristics. Discussed are the type and causes of low-frequency changes in meteorological parameters, radiation balance components, radiation in different spectral ranges, and chemical composition of precipitation. Demonstrated are possible mechanisms of the more significant increase observed in air temperature in Moscow as compared with that in Central Federal District and their connection with the greenhouse effect in the urban atmosphere.