Noise reduction and detection of weak, coherent signals through phase-weighted stacks

We present a new tool for efficient incoherent noise reduction for array data employing complex trace analysis. An amplitude-unbiased coherency measure is designed based on the instantaneous phase, which is used to weight the samples of an ordinary, linear stack. The result is called the phase-weighted stack (PWS) and is cleaned from incoherent noise. PWS thus permits detection of weak but coherent arrivals. The method presented can easily be extended to phase-weighted cross-correlations or be applied in the τ p domain. We illustrate and discuss the advantages and disadvantages of PWS in comparison with other coherency measures and present examples. We further show that our non-linear stacking technique enables us to detect a weak lower-mantle P -to- S conversion from a depth of approximately 840 km on array data. Hints of an 840 km discontinuity have been reported; however, such a discontinuity is not yet established due to the lack of further evidence.     

Assessment of environmental quality and inland water pollution using biomarker responses in caged carp (Cyprinus carpio): Use of a bioactivation:detoxication ratio as a Biotransformation Index (BTI)

In the present study the bioaccumulation of poly chlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) as well as the responses of a suite of biochemical parameters were investigated in a standardized carp (Cyprinus carpio) fish line. Carps were caged for 2 to 8 weeks at two Amsterdam freshwater sites: the relatively unpolluted Outer IJ and the heavily polluted Volgermeerpolder. The primary objective of the experiments was to develop a reliable and reproducible method to monitor the inland water pollution and to classify the environmental quality of freshwater sites. The highest tissue levels of organic trace pollutants were generally found in carp that was caged for at least four weeks at the polluted site. Hepatic phase I enzymes showed the highest pollution-induced responses, while phase II enzymes and serum transaminases were less sensitive. The antioxidant enzymes showed virtually no response to pollutants. In order to assess effects on the balance between bioactivation and detoxication the ratio between phase I (EROD) and phase II (GST or UDPGT) activities was introduced as a biotransformation index (BTI). Highest BTI values were observed in carp that was caged for 4 to 6 weeks at the polluted site. The BTI values decreased after eight weeks of exposure due to elevated phase II activities.     

The contribution of Dutch landscape painters to the conservation of geoheritage

Landscape images are a way to register geoheritage, and we have applied it here in a consideration of the landscapes of the Netherlands. Before the 1950s these landscapes were documented chiefly by landscape painters; with useful photographs of limited availability. We have looked through a large number of paintings of Dutch landscapes to assess their geoheritage value, and present here a first reconnaissance.     

Thermal state of the Roer Valley Graben,part of the European Cenozoic Rift System

We performed a detailed analysis of the thermal state of the Cenozoic Roer Valley Graben, the north–western branch of the European Cenozoic Rift System, based on a new set of temperature data. We developed a numerical technique for correcting bottom hole temperatures, including an evaluation of the uncertainty of thermal parameters. Comparison with drill stem test temperatures indicated that the uncertainty in corrected bottom hole temperatures using a two‐component numerical model is approximately ± 4 °C, which is much more accurate than the up to 15 °C errors encountered in often‐used line‐source or Horner correction methods. The subsurface temperatures and the derived regional heat flow estimates of 53 ± 6 to 63 ± 6 mW m^?2 show no significant difference between the central rift and the adjacent structural highs. The absence of an elevated heat flow is attributed to the low amount of lithospheric thinning during the Cenozoic rifting phase (β=1.06–1.15). A local thermal anomaly exceeding +10 °C was found in five wells in the north–western part of the rift basin at depths of 1000–1500 m, and is most likely caused by the upward flow of fluids along faults, whereas lower temperatures in the upper 1500 m in the southern part of the rift basin could indicate cooling by topography‐driven groundwater flow. Conflicting ideas exist on the active or passive rifting mechanisms responsible for the formation of the different rift basins of European Cenozoic Rift System. The low spatial variation in heat flow found in this study suggests that the mechanism responsible for forming the Roer Valley Graben is passive rifting.     

A song of volumes,surfaces and fluxes: The case study of the Central Mallorca Depression (Balearic Promontory) during the Messinian Salinity Crisis

The Central Mallorca Depression (CMD) located in the Balearic Promontory (Western Mediterranean) contains a well-preserved evaporitic sequence belonging to the Messinian Salinity Crisis (MSC) salt giant, densely covered by high- and low-resolution seismic reflection data. It has been proposed recently that the MSC evaporitic sequence in the CMD could be a non-deformed analogue of the key MSC area represented by the Caltanissetta Basin in Sicily. This presumed similarity makes the CMD an interesting system to better understand the MSC events. Physics-based box models of the water mixing between sub-basins, built on conservation of mass of water and salt, help constrain the hydrological conditions under which evaporites formed during the MSC. Those models have been widely used in the literature of the MSC in the past two decades. They have been mostly applied to the Mediterranean Sea as a whole focusing on the Mediterranean–Atlantic connection, or focusing on the influence of the Sicily Sill connecting the Western and Eastern Mediterranean Sea. In this study, we apply a downscaled version of such modelling technique to the CMD. First, we quantify the present-day volumes of the MSC units. We then use a reconstructed pre-MSC paleo-bathymetry to model salinity changes as a function of flux exchanges between the CMD and the Mediterranean. We show that a persistent connection between the CMD and the Mediterranean brine near gypsum saturation can explain volume of Primary Lower Gypsum under a sea level similar to the present. For the halite, on the contrary, we show that the observed halite volume cannot be deposited from a connected CMD-Mediterranean scenario, suggesting a drawdown of at least 850 m (sill depth) is necessary. Comparison between the deep basin halite volume and that of the CMD shows that it is possible to obtain the observed halite volume in both basins from a disconnected Mediterranean basin undergoing drawdown, although determining the average salinity of the Western Mediterranean basin at the onset of drawdown requires further investigation.     

Tidal-Fluvial and Estuarine Processes in the Lower Columbia River: II. Water Level Models,Floodplain Wetland Inundation,and System Zones

Spatially varying water-level regimes are a factor controlling estuarine and tidal-fluvial wetland vegetation patterns. As described in Part I, water levels in the Lower Columbia River and estuary (LCRE) are influenced by tides, river flow, hydropower operations, and coastal processes. In Part II, regression models based on tidal theory are used to quantify the role of these processes in determining water levels in the mainstem river and floodplain wetlands, and to provide 21-year inundation hindcasts. Analyses are conducted at 19 LCRE mainstem channel stations and 23 tidally exposed floodplain wetland stations. Sum exceedance values (SEVs) are used to compare wetland hydrologic regimes at different locations on the river floodplain. A new predictive tool is introduced and validated, the potential SEV (pSEV), which can reduce the need for extensive new data collection in wetland restoration planning. Models of water levels and inundation frequency distinguish four zones encompassing eight reaches. The system zones are the wave- and current-dominated Entrance to river kilometer (rkm) 5; the Estuary (rkm-5 to 87), comprised of a lower reach with salinity, the energy minimum (where the turbidity maximum normally occurs), and an upper estuary reach without salinity; the Tidal River (rkm-87 to 229), with lower, middle, and upper reaches in which river flow becomes increasingly dominant over tides in determining water levels; and the steep and weakly tidal Cascade (rkm-229 to 234) immediately downstream from Bonneville Dam. The same zonation is seen in the water levels of floodplain stations, with considerable modification of tidal properties. The system zones and reaches defined here reflect geological features and their boundaries are congruent with five wetland vegetation zones.