The 2010 MW 6.8 Yushu (Qinghai, China) earthquake: constraints provided by InSAR and body wave seismology

By combining observations from satellite radar, body wave seismology and optical imagery, we have determined the fault segmentation and sequence of ruptures for the 2010 Mw 6.8 Yushu (China) earthquake. We have mapped the fault trace using displacements from SAR image matching, interferometric phase and coherence, and 2.5 m SPOT-5 satellite images. Modeling the event as an elastic dislocation with three segments fitted to the fault trace suggests that the southeast and northwest segments are near vertical, with the central segment dipping 70° to the southwest; slip occurs mainly in the upper 10 km, with a maximum slip of 1.5 m at a depth of 4 km on the southeastern segment. The maximum slip in the top 1 km (i.e., near surface) is up to 1.2 m, and inferred locations of significant surface rupture are consistent with displacements from SAR image matching and field observations. The radar interferograms show rupture over a distance of almost 80 km, much larger than initial seismological and field estimates of the length of the fault. Part of this difference can be attributed to slip on the northwestern segment of the fault being due to an Mw 6.1 aftershock two hours after the main event. The remaining difference can be explained by a non-uniform slip distribution with much of the moment release occurring at depths of less than 10 km. The rupture on the central and southeastern segments of the fault in the main shock propagated at a speed of 2.5 km/s southeastward toward the town of Yushu located at the end of this segment, accounting for the considerable building damage. Strain accumulation since the last earthquake on the fault segment beyond Yushu is equivalent to an Mw 6.5 earthquake

On validating predictions of plant motion in coupled biomechanical-flow models

Recent developments in integrated biomechanical-flow models have enabled the prediction of the influence of vegetation on the flow field and associated feedback processes. However, to date, such models have only been validated on the hydraulic predictions and/or mean plant position. Here we introduce an approach where dynamic surrogate plant motion, measured directly in flume experiments, is used to allow a validation approach capable of assessing the accuracy of time-dependent flow–vegetation interaction within a numerical model. We use this method to demonstrate the accuracy of an existing Euler–Bernoulli beam model in predicting both mean and dynamic plant position through time and space

High-resolution numerical modelling of flow-vegetation interactions

In this paper, we present and apply a new three-dimensional model for the prediction of canopy-flow and turbulence dynamics in open-channel flow. The approach uses a dynamic immersed boundary technique that is coupled in a sequentially staggered manner to a large eddy simulation. Two different biomechanical models are developed depending on whether the vegetation is dominated by bending or tensile forces. For bending plants, a model structured on the Euler–Bernoulli beam equation has been developed, whilst for tensile plants, an N-pendula model has been developed. Validation against flume data shows good agreement and demonstrates that for a given stem density, the models are able to simulate the extraction of energy from the mean flow at the stem-scale which leads to the drag discontinuity and associated mixing layer

Does the canopy mixing layer model apply to highly flexible aquatic vegetation? Insights from numerical modelling

Vegetation is a characteristic feature of shallow aquatic flows such as rivers, lakes and coastal waters. Flow through and above aquatic vegetation canopies is commonly described using a canopy mixing layer analogy which provides a canonical framework for assessing key hydraulic characteristics such as velocity profiles, large-scale coherent turbulent structures and mixing and transport processes for solutes and sediments. This theory is well developed for the case of semi-rigid terrestrial vegetation and has more recently been applied to the case of aquatic vegetation. However, aquatic vegetation often displays key differences in morphology and biomechanics to terrestrial vegetation due to the different environment it inhabits. Here we investigate the effect of plant morphology and biomechanical properties on flow–vegetation interactions through the application of a coupled LES-biomechanical model. We present results from two simulations of aquatic vegetated flows: one assuming a semi-rigid canopy and the other a highly flexible canopy and provide a comparison of the associated flow regimes. Our results show that while both cases display canopy mixing layers, there are also clear differences in the shear layer characteristics and turbulent processes between the two, suggesting that the semi-rigid approximation may not provide a complete representation of flow–vegetation interactions

Sticky stuff : redefining bedform prediction in modern and ancient environments

This work was funded by the UK Natural Environment Research Council (NERC) under the COHBED project (NE/1027223/1). Paterson was funded by the Marine Alliance for Science and Technology for Scotland (MASTS).The dimensions and dynamics of subaqueous bedforms are well known for cohesionless sediments. However, the effect of physical cohesion imparted by cohesive clay within mixed sand-mud substrates has not been examined, despite its recognized influence on sediment stability. Here we present a series of controlled laboratory experiments to establish the influence of substrate clay content on subaqueous bedform dynamics within mixtures of sand and clay exposed to unidirectional flow. The results show that bedform dimensions and steepness decrease linearly with clay content, and comparison with existing predictors of bedform dimensions, established within cohesionless sediments, reveals significant over-prediction of bedform size for all but the lowermost clay contents examined. The profound effect substrate clay content has on bedform dimensions has a number of important implications for interpretation in a range of modern and ancient environments, including reduced roughness and bedform heights in estuarine systems and the often cited lack of large dune cross-sets in turbidites. The results therefore offer a step change in our understanding of bedform formation and dynamics in these, and many other, sedimentary environments.Publisher PDFPeer reviewe

IGBP Report

The Kalahari Transect is proposed as one of IGBPs Transects (see Koch et al. 1995 [IGBP Report 36]). It is located so as to span the gradient between the arid subtropics and the moist tropics in southern Africa, a zone potentially susceptible to changes in the global precipitation pattern. Its focus is the relationships between the structure and function of ecosystems and their large-scale biophysical and human drivers (climate, atmosphere and land use). The Kalahari Transect spans a strong climatic gradient in southern Africa, from the arid south to the humid north, while remaining on a single broad soil type, the deep sands of the Kalahari basin. The vegetation ranges over the length of the transect from shrubland through savannas and woodlands to closed evergreen tropical forest, with land uses ranging from migratory wildlife systems, through pastoralism, subsistence cropping to forestry. The objectives of the Kalahari Transect activity are to: build an active network of regional and international researchers around the issue of ecosystem structure and function in savanna woodlands undergoing climatic and land use change; quantify the current and future role of southern African savanna woodlands in the global carbon, water and trace gas budgets and the degree of dependence of these budgets on climate and land use change; develop a predictive understanding of future changes in southern African savannas and woodlands on sandy soils, including their capacity to deliver forage, timber and other products. A five year project is proposed, commencing in 1997. The project revolves around four themes: vegetation structure, composition and dynamics; biogeochemistry, trace gas emissions and productivity; resource use and management and water and energy balance. These themes define the minimum set of processes necessary for understanding of the Kalahari system

Changes in Plasma Fibronectin Isoform Levels Predict Distinct Clinical Outcomes in Critically Ill Patients

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A Nondestructive Method to Identify POP Contamination Sources in Omnivorous Seabirds

Persistent organic pollutants (POPs) are present in almost all environments due to their high bioaccumulation potential. Especially species that adapted to human activities, like gulls, might be exposed to harmful concentrations of these chemicals. The nature and degree of the exposure to POPs greatly vary between individual gulls, due to their diverse foraging behavior and specialization in certain foraging tactics. Therefore, in order clarify the effect of POP-contaminated areas on gull populations, it is important to identify the sources of POP contamination in individual gulls. Conventional sampling methods applied when studying POP contamination are destructive and ethically undesired. The aim of this literature review was to evaluate the potential of using feathers as a nondestructive method to determine sources of POP contamination in individual gulls. The reviewed data showed that high concentrations of PCBs and PBDEs in feathers together with a large proportion of less bioaccumulative congeners may indicate that the contamination originates from landfills. Low PCB and PBDE concentrations in feathers and a large proportion of more bioaccumulative congeners could indicate that the contamination originates from marine prey. We propose a nondestructive approach to identify the source of contamination in individual gulls based on individual contamination levels and PCB and PBDE congener profiles in feathers. Despite some uncertainties that might be reduced by future research, we conclude that especially when integrated with other methods like GPS tracking and the analysis of stable isotopic signatures, identifying the source of POP contamination based on congener profiles in feathers could become a powerful nondestructive method

Relating imperatives to action

The aim of this chapter is to provide an analysis of the use of logically complex imperatives, in particular, imperatives of the form Do A1 or A2 and Do A, if B. We argue for an analysis of imperatives in terms of classical logic which takes into account the influence of background information on imperatives. We show that by doing so one can avoid some counter-intuitive results which have been associated with analyses of imperatives in terms of classical logic. In particular, I address Hamblin's observations concerning rule-like imperatives and Ross' Paradox. The analysis is carried out within an agent-based logical framework. This analysis explicates what it means for an agent to have a successful policy for action with respect to satisfying his or her commitments, where some of these commitments have been introduced as a result of imperative language use

Phosphorus retention and transformation in a dammed reservoir of the Thames River, Ontario: Impacts on phosphorus load and speciation

Extensive efforts are underway to reduce phosphorus (P) export from the Lake Erie watershed. On the Canadian side, the Thames River is the largest tributary source of P to Lake Erie’s western basin. However, the role of dams in retaining and modifying riverine P loading to the lake has not been comprehensively evaluated. We assessed whether Fanshawe Reservoir, the largest dam reservoir on the Thames River, acts as a source or sink of P, using year-round discharge and water chemistry data collected in 2018 and 2019. We also determined how in-reservoir processes alter P speciation by comparing the dissolved reactive P to total P ratio (DRP:TP) in upstream and downstream loads. Annually, Fanshawe Reservoir was a net sink for P, retaining 25% (36 tonnes) and 47% (91 tonnes) of TP in 2018 and 2019, respectively. Seasonally, the reservoir oscillated between a source and sink of P. Net P release occurred during the spring of 2018 and the summers of 2018 and 2019, driven by internal P loading and hypolimnetic discharge from the dam. The reservoir did not exert a strong influence on DRP:TP annually, but ratio increases occurred during both summers, concurrent with water column stratification. Our analysis demonstrates that Fanshawe Reservoir is not only an important P sink on the Thames River, but also modulates the timing and speciation of P loads. We therefore propose that the potential of using existing dam reservoirs to attenuate downstream P loads should be more thoroughly explored alongside source based P mitigation strategies.Canada-Ontario Agreement on Great Lakes Water Quality and Ecosystem Health || Canada First Research Excellence Fund through the Lake Futures project of the Global Water Futures