The Marsdenian (Namurian R2) succession west of Blackburn: Implications for the evolution of Pennine Delta Systems

A recently driven sewer tunnel west of Blackburn has shown the presence of a thick turbidite sequence between the R. gracile and R. bilingue Goniatite Bands. Above the R. bilingue Band, turbidites pass up through delta slope deposits into delta top fluviatile sandstones, derived from the northeast. The section provides evidence for the westward limit of advance of the pre-R. gracile Kinderscoutian delta slope and also enables a more accurate R₂ isopachyte map to bc drawn.     

Seismic isolation of cable‐stayed bridges for near‐field ground motions

This study examines the efficacy of using seismic isolation to favorably influence the seismic response of cable‐stayed bridges subjected to near‐field earthquake ground motions. In near‐field earthquake ground motions, large amplitude spectral accelerations can occur at long periods where many cable‐stayed bridges have significant structural response modes. This combination of factors can result in large tower accelerations and base shears. In this study, lead–rubber bearing seismic isolators were modeled for three cable‐stayed bridges, and three cases of isolation were examined for each bridge. The nine isolated bridge configurations, plus three non‐isolated configurations as references, were subjected to near‐field earthquake ground motions using three‐dimensional time‐history analyses. Introduction of a small amount of isolation is shown to be very beneficial in reducing seismic accelerations and forces while at the same time producing only a modest increase in the structural displacements. There is a low marginal benefit to continue to increase the amount of isolation by further lengthening the period of the structure because structural forces and accelerations reduce at a diminishing rate whereas structural displacements increase substantially. In virtually all cases the base shears in the isolated bridges were reduced by at least 50several instances by up to 80individual near‐field records showed large variability from one record to the next, with coefficients of variation about the mean as large as 50assessing the characteristics of near‐field ground motion for use in isolation design of cable‐stayed bridges. Copyright © 2003 John Wiley & Sons, Ltd.     

A methodology for dynamic analysis of linear structure-foundation systems with local non-linearities

An efficient computational technique is presented for the dynamic analysis of large linear structural systems with local non-linearities. The earthquake response evaluation for many practical structures belongs to this class of problems. The technique provides a rational approach to the earthquake-resistant design of structure-foundation systems with predetermined non-linearities occurring along the structure-foundation interface. Various possibilities for base isolation systems are naturally fitted within the proposed framework. In particular, we address uplifting of the structure as a natural base isolation concept. We use the dynamic substructuring technique and an efficient numerical algorithm which accommodates non-proportional damping as a consistent way to reduce significantly the computational effort, which is in sharp contrast to the vast majority of ad-hoc simplified models used for the same purpose. A numerical example which demonstrates the vibration isolation effect when the uplifting of the concrete gravity dam occurs is also presented.     

The cold-water coral Lophelia pertusa (Scleractinia) and enigmatic seabed mounds along the north-east Atlantic margin: are they related?

In this study, an updated distribution of Lophelia pertusa between the Porcupine Seabight and Norwegian shelf is presented. It seems unlikely that enigmatic mound structures observed at water depths of more than 570 m during acoustic seabed surveys, particularly to the west of the Shetland Islands, are related to the occurrence of L. pertusa. At these depths in the Faroe-Shetland Channel, the predominant influence of cold Arctic water precludes its growth. Iceberg dumpsites are also considered unlikely explanations for the origin of these mounds, and they are interpreted as most likely to be related to the release of fluids at the seabed. When mound structures were investigated, no scleractinian corals were recovered at water depths >500 m. This study shows the importance of seabed temperature as an environmental control on cold-water coral distribution. The significance of cold-water coral habitats in sustaining high levels of local-scale biodiversity is now becoming apparent in parallel with increased hydrocarbon extraction and fishing activity beyond the shelf edge. There is growing evidence that these areas have been marked by the passage of deep-water trawls. It seems likely that trawling activity has already reduced the extent of cold-water coral distribution in this region of the north-east Atlantic.     

Acoustic characteristics of fish bombing: potential to develop an automated blast detector

The use of explosives to catch fish has caused extensive damage to coral reefs throughout Southeast Asia, but the frequency with which they are used is largely unknown. The aim of this work is to develop a detection system capable of distinguishing underwater explosions from background noise, and locating their origin by triangulation. Blast signals have been recorded over a range of distances and the key features that differentiate them from background noise have been determined. For small charges the effective range of such a detector is more than 12 km and may extend up to 50 km depending on the mass of the charges being used. Such a system would help to determine the scale of the problem, identify areas at greatest risk and quantify the effectiveness of management intervention designed to control destructive fishing practices. It may assist with fisheries enforcement in some areas.     

Residence time of bedform-driven hyporheic exchange

Biogeochemical and ecological transformations in hyporheic zones are dependent on the timing of hyporheic exchange. We show through linked modeling of open channel turbulent flow, groundwater flow, and solute transport that the residence time distributions of solutes advected by hyporheic flow induced by current–bedform interaction follow power-laws. This tailing behavior of solutes exiting the sediments is explained by the presence of multiple path lengths coupled with very large variability in Darcy flow velocity, both occurring without heterogeneity in sediment permeability. Hyporheic exchange through bedforms will result in short-time fractal scaling of stream water chemistry.     

U–Pb dating of zircon in hydrothermally altered rocks as a correlation tool: Application to the Mangakino geothermal field,New Zealand

Recognition and correlation of rock units within geothermal fields is often hampered by high degrees of alteration that obscure primary mineralogies and lithological boundaries, and preclude direct dating by radiometric techniques. Magmatic zircons are commonly present in silicic volcanic rocks, where zircon saturation was achieved and zircons crystallized up to the point of eruption. Young zircons are highly resistant to hydrothermal alteration and can yield a record of their crystallization ages in otherwise heavily altered rocks. Zircon crystallization-age spectra have been obtained by SIMS techniques (SHRIMP-RG) from three samples of cuttings and a core sample from ignimbrite penetrated in 3 drillholes up to ~ 3.2 km deep at the Mangakino geothermal field in New Zealand. The crystallization ages are similar between the drillcore and cutting samples, indicating that downhole mixing of cuttings has not been important, and showing collectively that volcanic units of closely similar ages are represented between ~ 1.4 and ~ 3.2 km depth. This is despite apparent changes in the inferred primary volcanic lithology that had led to earlier inferences that multiple ignimbrites of contrasting age were present in this depth interval. Comparisons of zircon crystallization-age spectra and inferred primary mineralogical characteristics from the drillhole samples with surficial ignimbrites that crop out west of Mangakino suggest that the boreholes have entered a > 1.8-km-thick intracaldera fill of ignimbrite generated in the closely-spaced Kidnappers and Rocky Hill eruptions at ~ 1 Ma.     

Statistical algorithms accounting for background density in the detection of UXO target areas at DoD munitions sites

Statistically defensible methods are presented for developing geophysical detector sampling plans and analyzing data for munitions response sites where unexploded ordnance (UXO) may exist. Detection methods for identifying areas of elevated anomaly density from background density are shown. Additionally, methods are described which aid in the choice of transect pattern and spacing to assure with degree of confidence that a target area (TA) of specific size, shape, and anomaly density will be identified using the detection methods. Methods for evaluating the sensitivity of designs to variation in certain parameters are also discussed. Methods presented have been incorporated into the Visual Sample Plan (VSP) software (free at ) and demonstrated at multiple sites in the United States. Application examples from actual transect designs and surveys from the previous two years are demonstrated.     

Evaluating ecological quality in the north-eastern Black Sea coastal zone

Anthropogenic pressures have resulted in measurable impacts on the coastal ecosystems of the northern (Sevastopol Bay, Ukraine) and eastern (Batumi aquatoria, Georgia) Black Sea. Indices suggest that major impacts are relatively localized and are comparable to similar situations in the northern Atlantic. In contrast, biodiversity was appreciably lower than from comparable north Atlantic waters. The number of macrobenthic species was typically round 50, less than half the number that might be expected from similar exercises in US or European waters. Site-specific indices likewise indicated a somewhat lower diversity within communities, yielding metrics which would indicate a measure of stress in N. Atlantic situations. Microbial status was generally good, although regions close to urbanisation did not comply with standards laid down in the current EC Bathing Water Directive (76/EC/160). Likewise viruses were more commonly, although not exclusively, associated with urban locations, as were phages. Microbial investigation of the sediments confirmed the presence of heterotrophic and oil-oxidising bacteria. Abundance of the latter was closely correlated to the degree of oil contamination of the sediments, and to temperature, although for both, the results showed that the increase in bacterial abundance did level off beyond a certain point. Numbers of oil-oxidising bacteria in the water column displayed a classical response to temperature, with abundance doubling over a 10-degree C rise in temperature. Overall the results suggest that while indices in current use are useful in evaluating coastal quality in the Black Sea, some adjustments would be necessary especially in the establishment of baseline or reference values.