Influence of earthquakes on the stability of slopes

Earthquakes are a major trigger for instability of natural and man-made slopes. Often the instability of slopes due to an earthquake causes more destruction and kills more people than the actual earthquake itself. A comparison is made between different methodologies to analyze the potential stability of slopes during earthquakes. Theoretically, it seems simple to calculate the stability of a slope during an earthquake. In reality, however, the stability is influenced by so many parameters that are either not known or which influence is so poorly known that a decent estimation of stability cannot be made. Offshore the situation is worse because proper data required for stability calculations are even less available than onshore. On- and offshore, erosion and weathering create continuously slopes that may become unstable during a future earthquake, offshore also sedimentation creates continuously new slopes. Another fundamental problem in stability analysis is the complicated and largely unknown behavior of seismic waves in three-dimensions in natural materials. The lack of accurate data and the unknown behavior of seismic waves in three-dimensions make estimations of slope stability during an earthquake unreliable.     

Human alteration of groundwater–surface water interactions (Sagittario River,Central Italy): implication for flow regime,contaminant fate and invertebrate response

Many rivers worldwide are undergoing severe man-induced alterations which are reflected also in changes of the degree of connectivity between surface waters and groundwater. Pollution, irrigation withdrawal, alteration of freshwater flows, road construction, surface water diversion, soil erosion in agriculture, deforestation and dam building have led to some irreversible species losses and severe changes in community composition of freshwater ecosystems. Taking into account the impact of damming and flow diversion on natural river discharge, the present study is aimed at (i) evaluating the effects of anthropogenic changes on groundwater/surface water interactions; (ii) analyzing the fate of nitrogenous pollutants at the floodplain scale; and (iii) describing the overall response of invertebrate assemblages to such changes. Hydrogeological, geochemical and isotopic data revealed short- and long-term changes in hydrology, allowing the assessment of the hydrogeological setting and the evaluation of potential contamination by nitrogen compounds. Water isotopes allowed distinguishing a shallow aquifer locally fed by zenithal recharge and river losses, and a deeper aquifer/aquitard system fed by surrounding carbonate aquifers. This system was found to retain ammonium and, through the shallow aquifer, release it in surface running waters via the hyporheic zone of the riverbed. All these factors influence river ecosystem health. As many environmental drivers entered in action offering a multiple-component artificial environment, a clear relationship between river flow alteration and benthic and hyporheic invertebrate diversity was not found, being species response driven by the combination of three main stressors: ammonium pollution, man-induced changes in river morphology and altered discharge regime.     

Mineralogy and geochemistry of platinum-group elements in the Aguablanca Ni-Cu deposit (SW Spain)

Summary The Aguablanca Ni-Cu-(PGE) magmatic sulphide deposit is associated with a magmatic breccia located in the northern part of the Aguablanca gabbro (SW, Iberia). Three types of ores are present: semi-massive, disseminated, and chalcopyrite-rich veined ore. The principal ore minerals are pyrrhotite, pentlandite and chalcopyrite. A relatively abundant platinum-group mineral (PGM) assemblage is present and includes merenskyite, melonite, michenerite, moncheite and sperrylite. Moreover, concentrations of base and precious metals and micro-PIXE analyses were obtained for the three ore-types. The mineralogy and the mantle-normalised chalcophile element profiles strongly suggest that semi-massive ore represents mss crystallisation, whereas the disseminated ore represents an unfractionated sulphide liquid and the chalcopyrite-rich veined ore a Cu-rich sulphide liquid. Palladium-bearing minerals occur commonly enclosed within sulphides, indicating a magmatic origin rather than hydrothermal. The occurrences and the composition of these minerals suggest that Pd was initially dissolved in the sulphides and subsequently exsolved at low temperatures to form bismutotellurides. Negative Pt and Au anomalies in the mantle-normalised chalcophile element profiles, a lack of Cu-S correlation and textural observations (such as sperrylite losing its euhedral shape when in contact with altered minerals) suggest partial remobilisation of Pt, Au and Cu by postmagmatic hydrothermal fluids after the sulphide crystallisation. Authors’ addresses: R. Pi?a, L. Ortega, R. Lunar, Departamento de Cristalografía y Mineralogía, Facultad de Geología, Universidad Complutense de Madrid, ES-28040 Madrid, Spain; F. Gervilla, Facultad de Ciencias, Instituto Andaluz de Ciencias de la Tierra, Universidad de Granada-CSIC, Avda. Fuentenueva, s/n, ES-18002 Granada, Spain     

A DNA tracer used in column tests for hydrogeology applications

Tracing techniques are commonly used to investigate groundwater quality and dynamics, as well as to measure the hydrogeological parameters of aquifers. The last decade has seen a growing interest in environmentally friendly tracers, including single-stranded DNA molecules. In this study, an electrolytic tracer and a synthetic DNA tracer are comparatively evaluated in laboratory scale tests to assess their potential application in field studies aimed at investigating groundwater environments. A real-time quantitative Polymerase Chain Reaction assay was developed and optimized to detect and quantify the DNA tracer, while tracer column tests were performed to investigate the DNA tracer behavior and to compare it to the electrolytic tracer. The results show that the DNA tracer has an almost pure convective flow, while the KCl tracer experiences dispersive behavior. The tracing method proposed can be applied in hydrogeological field studies involving calcareous fractured rock systems, with the DNA tracer particularly suitable in tracing karst systems, which are often characterized by several conduits of flow. To test the DNA tracer in operation, a preliminary test was conducted in the field.     

Effect of the wind acceleration magnitude during the first stages of the wind-wave generation process

Ocean Dynamics - A comprehensive analysis of the wavefield evolution under accelerated wind conditions provides an essential contribution to understanding the wind-wave generation process. A set of...     

Two Brazilian archaeological sites investigated by GPR: Serrano and Morro Grande

The application of the ground penetrating radar (GPR) at two archaeological sites, Serrano and Morro Grande, situated in Araruama County, Rio de Janeiro, Brazil, aids the study of a prehistoric indigenous culture, associated with the “Tupinambá” that inhabited the region during prehistoric times.The archaeological remains of the study area are mainly characterized by pottery artifacts for several uses, including funerary urns, which were buried within layers of sand and clay. Several profiles were acquired using a RAMAC system, with a 200 and 400 MHz frequency antennae. At the Serrano site, the profiles were acquired around some partially exposed pottery shards, due to sand exploitation. The resultant profiles provided a response model to guide the interpretation of new profiles acquired at other sites in the area, which present similar characteristics.The results showed the great importance of the dielectric permittivity contrast which exists between the targets and the host media, in order for possibly significant features to be identified in radar data.     

Geophysical-Archaeological Survey in Lake Tequesquitengo,Morelos, Mexico

In August 2009, a marine geophysical survey was conducted in Lake Tequesquitengo (located in the state of Morelos, Mexico) to delineate the extent of the remains of a small town that has been submerged since the mid 19th century. The survey consists of the acquisition and mapping of magnetic, single beam bathymetric and side-scan sonar data. A dual receiver marine GPS navigation system was used to position the boat during the survey. Except for the larger structural remains that are visible on the side scan sonar images, the magnetic anomaly map proved to be most useful in delineating the extent of the town. These anomalies exhibit short wavelength components in the area surrounding a submerged church, with the shortest wavelength components being confined to the area immediately east of the church. These short wavelength components are only observed near the church; therefore, we propose that they delineate the buried remnants of the submerged town.     

Non-invasive lab test in the monitoring of vadose zone contaminated by light non-aqueous phase liquid

We discuss a strategy capable of a quantitative long-term monitoring of water saturation and volume variation of light non-aqueous phase liquids in the soil. The goal was reached monitoring a controlled sand cell contaminated with classical gasoline over 124 days, using geophysical methods such as electrical resistivity tomography, induced polarization and ground penetrating radar. We show that empirical relations, linking the water saturation to the physical parameters measured as resistivity from electrical resistivity tomography and travel time from georadar with advanced processing, are good tools for this purpose. The consistence of the proposed process is validated by both good overlap of results carried out from electrical resistivity tomography and georadar and theoretical models simulating the actual experiment.     

Magma mixing and convective compositional layering within the Vesuvius magma chamber

The pumice-fall deposits of the last two Plinian eruptions of Vesuvius-a.d. 79 Pompei and 3700 b.p. Avellino-show a marked vertical compositional variation from white phonolite at the base to grey tephritic phonolite at the top. In both Avellino and Pompei sequences a compositional gap separates white from grey pumice. Grey and white pumice have distinct Sr and Nd isotopic compositions (grey pumice: ⁸⁷Sr/³⁶Sr=0.70749-56, ¹⁴³Nd/¹⁴⁴Nd=0.512507 for Pompei; 0.70760-69, 0.512504 for Avellino; white pumice: 0.70757-78 for Pompei; 0.70729-42 for Avellino). K-feldspar separated from both grey and white pumice has, in all cases, a white ⁸⁷Sr/⁸⁶Sr ratio (0.70766-79 for Pompei, 0.70728-33 for Avellino). The observed variations are interpreted as reflecting a pre-eruptive zonation of the magma chamber. Although mineralogical evidence of interaction between magma and calcareous country rocks exists in both eruptions, crustal contamination has not significantly modified the isotopic signatures of the erupted products. Petrographic and isotopic evidence of syneruptive magma mingling occur in Pompei grey pumice as well as in Avellino white and grey pumice, but they do not fully explain all the observed geochemical and isotopic variations. These variations are related to the complex refilling history of the magmatic system and result by fractional crystallization and mixing processes acting within the magma chamber. Preliminary data from other Plinian and subplinian sruptions of the Somma-Vesuvius point out the repeticive behaviour of ⁸⁷Sr/⁸⁶Sr variation in the last 25 000 years, hence suggesting a single magma chamber and continuity of the feeding system.