Introduction

Marine Geophysical Research -     

Changes in beach water table elevation during neap and spring tides on a sandy estuarine beach, Delaware Bay, New Jersey

A field investigation of temporal and spatial changes in wind and wave characteristics, runup and beach water table elevation was conducted on the foreshore of an estuarine beach in Delaware Bay during neap (April 9, 1995) and spring (April 16, 1995) tides under low wave-energy conditions. The beach has a relatively steep, sandy foreshore and semi-diurnal tides with a mean range of 1.6 m and a mean spring range of 1.9 m. Data from a pressure transducer placed on the low tide terrace reveal a rate of rise and fall of the water level on April 16 of 0.09 mm s⁻¹ resulting in a steeper tidal curve than the neap tide on April 9. Data from three pressure transducers placed in wells in the intertidal foreshore reveal that the landward slope of the water table during the rising neap tide was lower than the slope during spring tide, and there was a slower rate of fall of the beach water table relative to the fall of the tide. Wave heights were lower on April 9 (significant height from 17.1 min records <0.16 m). The water table elevation was 0.08 m higher than the water in the bay at the time of high water, when maximum runup elevation was 0.29 m above high water and maximum runup width was 2.0 m. The elevation of the water table was 0.13 m higher than the maximum elevation of water level in the bay 74 min after high water, when wave height was 0.12 m and wave period was 2.7 s. The use of mean bay water level at high tide will underpredict the elevation of the water table in the beach, and demarcation of biological sampling stations across the intertidal profile based on mean tide conditions will not accurately reflect the water content of the sandy beach matrix.     

Making ends meet, in the household and on the planet

Policy-making in relation to sustainable development is usually at the national (or, in relation to climate change, the global) level, yet the consumption it seeks to modify takes place at the household level. If households all ‘made ends meet’ in the same way then the much-relied upon notion of per capita consumption would be valid and we could rely on ‘top-down’ modelling to guide policy. Cultural Theory, however, predicts that there are five socially viable ways of making ends meet, and that all of them will be found (in varying proportions) within any nation. This prediction has been tested on a sample of 220 British households and shown to be well supported. Top-down modelling, it is argued, has to give way to a constructive interplay between the reflexive policy-maker and a plurally responsive citizenry. This revised version was published online in August 2006 with corrections to the Cover Date.     

Determination of Mislocation Vectors to Evaluate bias at GSETT-3 primary stations

Using the database provided by the Reviewed Event Bulletins (REBs) for the first 2.5 years of the Group of Scientific Experts Technical Test-3 (GSETT-3) experiment, we compiled mislocation vectors for both arrays and selected three-component stations of the primary network from the published slowness and azimuth information gained through f-k- and polarization analysis. Imposing constraints such as a minimum signal-to-noise ratio (SNR) and number of defining phases, we aim at eliminating location bias as the hypocentral parameters are taken from the REBs. Results from 14 arrays with apertures from about 1 km to more than 20 km are presented as well as from 18 three-component stations, which indicate that the mislocation vectors in many cases can improve location accuracy considerably. If these mislocation vectors are compiled to provide coverage of a sufficient portion of the slowness domain these empirical corrections can easily be applied prior to location processing. In the context of the Comprehensive Nuclear Test-Ban Treaty (CTBT), these mislocation patterns could be essential for providing accurate event location of suspicious low-magnitude events, as these location parameters will be used to pinpoint the area where to conduct an on-site inspection.     

Authigenic albite in carbonate rocks – a tracer for deep-burial brine migration?

Euhedral, post-depositional albite from the Eastern and Western Alps, the western Carpathians and some Greek islands was examined petrographically and geochemically to gain insights into the nature of feldspar reactions in carbonate rocks. This study focuses on coarsely crystalline, homogeneously nucleated albite in order to avoid problems related to the presence of inseparable detrital material in fine-grained albite varieties. All albite samples show a very restricted compositional variability and are typically ≥ 99 mol% Ab component. Unit-cell parameters determined by Rietveld analysis are slightly more variable than previously accepted, but confirm high Al–Si ordering characteristic of low albite. The oxygen isotopic composition of albite ranges from + 19·4‰ to + 28·3‰ VSMOW. There is no direct relationship between the δ¹⁸O value and the inferred temperature of albite formation, nor is there one with stoichiometry. The coarse crystal size (up to several millimetres in diameter), petrographic evidence showing albite cross-cutting stylolites, greater abundance of albite in carbonate rocks subject to high-grade diagenetic or weak metamorphic overprinting and available fluid inclusion data suggest that albite precipitation is favoured at higher temperatures in carbonates than in sandstones. Pore fluids were invariably brines, as suggested by the inferred high positive δ¹⁸O_fluid values, the common association of albite-bearing carbonates and evaporites and reports of saline fluid inclusions in albite. The presence of authigenic albite may thus be a useful tracer of palaeobrine–carbonate reactions, particularly in deep-burial and incipient metamorphic settings.     

Offshore aeolian sediment transport across a human‐modified foredune

Concepts derived from previous studies of offshore winds on natural dunes are evaluated on a dune maintained for shore protection during three offshore wind events. The potential for offshore winds to form a lee‐side eddy on the backshore or transfer sediment from the dune and berm crest to the water are evaluated, as are differences in wind speed and sediment transport on the dune crest, berm crest and a pedestrian access gap. The dune is 18–20 m wide near the base and has a crest 4.5 m above backshore elevation. Two sand‐trapping fences facilitate accretion. Data were obtained from wind vanes on the crest and lee of the dune and anemometers and sand traps placed across the dune, on the beach berm crest and in the access gap. Mean wind direction above the dune crest varied from 11 to 3 deg from shore normal. No persistent recirculation eddy occurred on the 12 deg seaward slope. Wind speed on the berm crest was 85–89% of speed at the dune crest, but rates of sediment transport were 2.27 times greater during the strongest winds, indicating that a wide beach overcomes the transport limitation of a dune barrier. Limited transport on the seaward dune ramp indicates that losses to the water are mostly from the backshore, not the dune. The seaward slope gains sand from the landward slope and dune crest. Sand fences causing accretion on the dune ramp during onshore winds lower the seaward slope and reduce the likelihood of detached flows during offshore winds. Transport rates are higher in access gaps than on the dune crest despite lower wind speeds because of flatter slopes and absence of vegetation. Transport rates across dunes and through gaps can be reduced using vegetation and raised walkover structures. Copyright © 2017 John Wiley & Sons, Ltd.     

The Daily Erosion Project – daily estimates of water runoff,soil detachment,and erosion

Water runoff and sediment transport from agricultural uplands are substantial threats to water quality and sustained crop production. To improve soil and water resources, farmers, conservationists, and policy‐makers must understand how landforms, soil types, farming practices, and rainfall interact with water runoff and soil erosion processes. To that end, the Iowa Daily Erosion Project (IDEP) was designed and implemented in 2003 to inventory these factors across Iowa in the United States. IDEP utilized the Water Erosion Prediction Project (WEPP) soil erosion model along with radar‐derived precipitation data and government‐provided slope, soil, and management information to produce daily estimates of soil erosion and runoff at the township scale (93 km² [36 mi²]). Improved national databases and evolving remote sensing technology now permit the derivation of slope, soil, and field‐level management inputs for WEPP. These remotely sensed parameters, along with more detailed meteorological data, now drive daily WEPP hillslope soil erosion and water runoff estimates at the small watershed scale, approximately 90 km² (35 mi²), across sections of multiple Midwest states. The revisions constitute a substantial improvement as more realistic field conditions are reflected, more detailed weather data are utilized, hill slope sampling density is an order of magnitude greater, and results are aggregated based on surface hydrology enabling further watershed research and analysis. Considering these improvements and the expansion of the project beyond Iowa it was renamed the Daily Erosion Project (DEP). Statistical and comparative evaluations of soil erosion simulations indicate that the sampling density is adequate and the results are defendable. The modeling framework developed is readily adaptable to other regions given suitable inputs. © 2017 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.     

Application of common reflection angle migration for imaging deformation structures in an inner accretionary wedge,Nankai Trough,Japan

To better image deformation structures within the inner accretionary wedge of the Nankai Trough, Japan, we apply common reflection angle migration to a legacy two-dimensional seismic data set acquired with a 6 km streamer cable. In this region, many seismic surveys have been conducted to study the seismogenic zone related to plate subduction. However, the details of the accreted sediments beneath the Kumano forearc basin are still unclear due to the poor quality of seismic images caused by multiple reflections, highly attenuated signals, and possibly complex geological structures. Generating common image gathers in the subsurface local angle domain rather than the surface offset domain is more advantageous for imaging geological structures that involve complex wave paths and poor illumination. By applying this method, previously unseen structures are revealed in the thick accreted sediments. The newly imaged geometric features of reflectors, such as the folds in the shallow part of the section and the deep reflectors with stepwise discontinuities, imply deformation structures with multiple thrust faults. The reflections within the deep accreted sediments (approximately 5 km) are mainly mapped to far angles (30°–50°) in the common reflection angles, which correspond to the recorded offset distances greater than 4.5 km. This result indicates that the far offset/angle information is critical to image the deformation structures at depth. The new depth image from the common reflection angle migration provides seismic evidence of multiple thrust faults and their relationship with the megathrust fault that is essential for understanding the structure and evolution of the Nankai Trough seismogenic zone.