Using DC resistivity tomography to detect and characterize mountain permafrost

Direct-current (DC) resistivity tomography has been applied to different mountain permafrost regions. Despite problems with the very high resistivities of the frozen material, plausible results were obtained. Inversions with synthetic data revealed that an appropriate choice of regularization constraints was important, and that a joint analysis of several tomograms computed with different constraints was required to judge the reliability of individual features. The theoretical results were verified with three field experiments conducted in the Swiss and the Italian Alps. At the first site, near Zermatt, Switzerland, the location and the approximate lateral and vertical extent of an ice core within a moraine could be delineated. On the Murtel rock glacier, eastern Swiss Alps, a steeply dipping boundary at its frontal part was observed, and extremely high resistivities of several MΩ indicated a high ice content. The base of the rock glacier remained unresolved by the DC resistivity measurements, but it could be constrained with transient EM soundings. On another rock glacier near the Stelvio Pass, eastern Italian Alps, DC resistivity tomography allowed delineation of the rock glacier base, and the only moderately high resistivities within the rock glacier body indicated that the ice content must be lower compared with the Murtel rock glacier.     

Comparative study of the inelastic response of base isolated buildings

This article presents a numeric comparative study of the inelastic structural response of base isolated buildings. The comparative study includes the following isolation systems: laminated rubber bearings, New Zealand one, pure friction and the frictional pendulum ones. The study is based on obtaining non‐linear response spectra for various design parameters using six earthquake records. Usually the base isolation of a new building seeks to maintain the structure in the linear elastic range. The response of old weak buildings or the response of new ones subjected to extreme earthquakes may not be, necessarily, in the aforementioned ideal elastic range. Consequently, it is important to characterize the response of isolated buildings responding inelastically. A conclusion from this research is that the isolators affect significantly the structural response of weak systems. Rubber isolators seem slightly less sensitive to plastification that may occur in the structure compared to friction isolators. Ductility demands in the structure are affected significantly by friction and neoprene protected systems, in particular sliding ones where larger demands are obtained. Copyright © 2002 John Wiley & Sons, Ltd.     

A vibrational spectroscopic study of the oxidation of pyrite by molecular oxygen

In situ flow-through attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy has been used to investigate the formation, and step-wise oxidation, of sulfoxyanions at the pyrite surface during oxidation by molecular oxygen. The surface was studied under two different pH regimes (pH 2.5 and pH 5.6) and under two light conditions (dark and ultraviolet light). It was experimentally observed that multiple sulfoxyanions were present at the pyrite surface during oxidation by molecular oxygen, spectroscopically illustrating the concept of sulfur step-wise oxidation. The results from photochemical experiments were complex and suggest a dependence on both pH and surface speciation.     

Aegean Sea ridge barrier-and-basin sedimentation patterns

An isopach map of the Aegean Sea, based on a regionally comprehensive seismic-profile network, reveals the highly irregular distribution of unconsolidated sediments of post-Miocene age. Geologically recent structural activity has considerably modified the seafloor configuration of the north and south Aegean, and depositional patterns are to varying degree related to the complex Aegean physiography. From north to south, a series of ridges, islands, and plateaus have acted as effective barriers behind which sediments are trapped, primarily in depressions. Sources of sediment in the north Aegean troughs and basins include rivers and suspensate-rich water masses; material was also provided by the erosion of plateaus and ridges during phases of Pliocene uplift and regressions and Quaternary eustatic low sea-level stands when the Aegean became virtually land-locked and isolated from the Black Sea. Volcanic as well as terrigenous material has accumulated in the central and south Aegean. However, the rapid depositional rates in the south Aegean are more closely related to the flow exchange with the Levantine Basin and the consequent ponding of material behind the Peloponnesus-Crete and Crete-Rhodes ridges.     

An Overview of Dissolved and Suspended Matter Fluxes in the Loire River Basin: Natural and Anthropogenic Inputs

The spatial and temporal distributions of major elements were investigated in the surface waters and in associated suspended matter at two sites of the upper Loire basin (Orleans and Brehemont) between 1995 and 1998.According to geochemical and isotopic patterns, the dissolved load appears to result from a process of mixing rainwater inputs, weathering processes of carbonate and silicate bedrock, and agricultural and urban inputs. Natural inputs influence 60% of water chemical composition at both sites. Annual dissolved fluxes were estimated to be 1300 10³ t/y at Orleans and 1620 10³ t/y at Brehemont. Major elements are transported mainly in the dissolved fraction. After correcting for atmospheric and anthropogenic inputs, the silicate specific export rate was calculated to be 11 t/y/km² throughout the basin and the carbonate specific export rate to be from 47 t/y/km² at Orleans to 23 t/y/km² at Brehemont.The suspended load appears to result from at least two particle reservoirs: a silicate reservoir and a carbonate reservoir. The silicate reservoir has a detrital origin, mainly during periods of high flow, while the carbonate reservoir has a detrital origin during periods of high flow and an authigenic origin during periods of low flow. Of the total annual flow of suspended matter, this authigenic material represents 16% at Orleans, 25% at Brehemont and 37% in the fluvial part of the estuary. After correcting authigenic inputs, the specific export rate due to mechanical weathering was estimated to be 8 t/y/km² throughout the Loire basin.