Granitoids of the Kongo Magmatic Zone of the Omolon Massif (Northeastern Russia): Rock Composition,Age, and Geodynamic Setting

Geotectonics - In our study we analyzed the composition of granitoid rocks within the Kongo magmatic zone of the Omolon median mass. The studied calc-alkaline granitoids cut through the Early...     

A simulation study of capillary transport,preferential retention and distribution of salts in historic sandstone buildings

Salt crystallisation is a major problem of deterioration in historic stone buildings, monuments and sculptures. The capillary rise of soil water is one of the primary sources of salts in stone structures, which evaporates leaving the salts behind. It has been noted that the spatial distribution profile of different species of salts crystallised in historic stone buildings is not homogeneous, i.e. different salts crystallise at different locations. The capillary transport and inhomogeneous spatial distribution of different salts in the porous building materials has been considered to be a result of solubility-dependent crystallisation; however, the factors responsible for this phenomenon are not clearly known. This paper aims to investigate the factors influencing the differential distribution of salts during capillary rise of soil water. In this study, the capillary transport of salts was simulated on two different sandstones—Locharbriggs, a Permo–Triassic, red sandstone and Stoke Hall, a Carboniferous, buff sandstone. The experiments were carried out under controlled environmental conditions to eliminate the possibility of evaporation-driven crystallisation of salts depending on their solubilities. The results indicate that fractionation or differential distribution of salts takes place even in the absence of evaporation and crystallisation. The sandstones exhibit properties like an ion exchange column, and ionic species present in the salt solution show differential distribution within the porous network of sandstone.     

The prospects for modernizing very broadband seismometers

This paper considers the possibilities for modernizing the KSESh broadband seismic station developed earlier at the IPE AS USSR. The goal of the modernization was to extend the frequency and dynamic ranges and to decrease nonlinear distortions. The ways and concrete methods for improving the mechanical construction and electronic components of the station are shown and the intermediate results are described. As preliminary estimates show, there is an opportunity to build devices with the velocimeter response up to 520–540 s periods on the basis of this pendulum.     

Geothermal energy release at the Solfatara of Pozzuoli (Phlegraean Fields): Phreatic and phreatomagmatic explosion risk implications

The H₂O, CO₂ and H₂S outputs at the Solfatara of Pozzuoli have been measured and a map of the exhaling areas has also been made. The energy released at the surface by the fluids has been estimated to be 10¹⁹ ergs/day.The presence of aquifers at Phlegraean Fields increases the phreatic and phreatomagmatic explosion risk.Our results suggest that even if an uprising magma may interact with water at depth, an explosion could occur only at the shallow levels of a few hundred meters. Since the transfer of energy toward the surface is favoured by the presence of fractures, a detailed analysis of the deep fracture network would help to evaluate the risk levels of the various areas of Phlegraean Fields.     

COMPUTER MODELING OF VERTICAL SEISMIC PROFILING*

There are numerous modeling techniques commonly employed for the computer simulation of seismic wave propagation. The capabilities of these techniques vary according to the theoretical foundations and subsequent approximations upon which the algorithms are based. This paper constitutes a comparative review of seven modeling methods: geometric ray theory, asymptotic ray theory, generalized ray theory, Kirchhoff wave theory, Fourier synthesis, finite differences, and finite elements. These methods can be categorized as ray or wave, acoustic or elastic, and can be contrasted according to their relative abilities to simulate such behavior as wave interference effects, diffractions, and mode conversions. As is implied by their names, geometric ray theory and asymptotic ray theory are both ray methods. The other five methods provide wave theory simulations. Geometric ray theory and Kirchhoff wave theory are normally implemented in acoustic form, while the other methods are readily adapted for computing elastic theory solutions. Generalized ray theory and Fourier synthesis are more limited in the complexity of geological model they can accommodate than are the other techniques. The methods which typically demand the greatest computer resources are the finite-difference and the finite-element techniques. All methods can incorporate at least some multiple events. Diffractions, however, are only inherent in the solutions computed by Kirchhoff wave theory, finite differences and finite elements. Attenuation is readily incorporated in both the Fourier synthesis and the finite-element methods. As an example of the application of seismic modeling, a geological model representative of a typical petroleum exploration target is used to compare vertical seismic profiles calculated by different modeling methods.