How Certain is Good Enough? Managing Data Quality and Uncertainty in Ordinal Citizen Science Data Sets for Evidence-Based Policies on Fresh Water

in Citizen Science: Theory and Practice (2023)

This study investigates surface water quality in Luxembourg with the help of citizen scientists. The fundamental question explored relates to uncertainty and judgements on what constitutes adequate data ... [more ▼]

This study investigates surface water quality in Luxembourg with the help of citizen scientists. The fundamental question explored relates to uncertainty and judgements on what constitutes adequate data sets, comparing official data and citizen science. The case study evaluates how gaps and uncertainties in official data for the United Nations Sustainable Development Goal 6 (UN SDG 6), Indicator 6.3.2 on water quality, and the EU Water Framework Directive (WFD), can be served with citizen science. In two Water Blitz sampling events organised in collaboration with the NGO Earthwatch, participants sampled water bodies at locations of their choice, using field kits to estimate nitrate and phosphate concentrations. Samples were collected (428 in total) over two weekend events, providing snapshots in time with a good geographic coverage of the water bodies across the country: 35% of nitrate and 29% of phosphate values were found to exceed thresholds used by the European Environment Agency to classify the nutrient content in water as good. Our study puts forward recommendations on how citizen science data can complement official monitoring by national agencies with a focus on how such data can be represented to serve the understanding and discussion of uncertainties associated with such ordinal data sets. The main challenge addressed is high levels of natural variation in nutrient levels with both natural and anthropogenic multi-factorial causes. In discussing the merits and limitations of citizen science data sets, the results of this study demonstrate that a particular strength of citizen science is the identification of pollution hotspots in small water bodies, which despite being critical for ecosystem wellbeing are often overlooked in official monitoring. In addition, citizen science increases public awareness and experiential learning about factors affecting surface water quality and policies concerning it. [less ▲]

Taking the Complex Dynamics of Human–Environment–Technology Systems Seriously: A Case Study in Doctoral Education at the University of Luxembourg

in Frontiers in Sustainability (2021), 2

Our existential sustainability challenges involve human–environment–technology systems that are complex, dynamic and tightly coupled. But at universities, knowledge, in teaching and research, is mostly ... [more ▼]

Our existential sustainability challenges involve human–environment–technology systems that are complex, dynamic and tightly coupled. But at universities, knowledge, in teaching and research, is mostly organized into discrete parcels, the disciplines. These are further divided into the categories of natural sciences, social science and the humanities. This paper addresses the question of how in their training of researchers, universities can equip them to better understand their roles and also to act as change agents. It describes a doctoral school course in transferable skills that is offered across faculties. The unique aim of the course is to provide a space for reflection on different research paradigms and the way they differ in their framing the role of a scientific researcher in pluralist societies that face existential challenges. The course introduces diverse more recent approaches to scientific inquiry that harness the potential of democratizing science in our networked knowledge society, including critical interdisciplinarity, post-normal science, citizen science and transformative sustainability science, that complement normal disciplinary research practices. [less ▲]

Microseismic Activity and Basement Controls on an Active Intraplate Strike-Slip Fault, Ceres–Tulbagh, South Africa

in Bulletin of the Seismological Society of America (2015), 105(3), 15401547

Earthquakes far from plate boundaries are poorly understood, because of few well-studied examples and uncertainty of what controls the location of these events. In 1969 a damaging local magnitude (ML) 6.3 ... [more ▼]

Earthquakes far from plate boundaries are poorly understood, because of few well-studied examples and uncertainty of what controls the location of these events. In 1969 a damaging local magnitude (ML) 6.3 strike-slip earthquake, with no surface expression, occurred in the Ceres–Tulbagh region in the South African stable continental interior. Here, we present a microseismic study of the Ceres–Tulbagh area, conducted over three months in 2012, in which 172 events recorded on at least three stations follow a Gutenberg–Richter relationship for −1.5 < ML < 0.5. The events delineate a 5 km wide, subvertical zone that is microseismically active to a depth of 15 km. This fault zone is subparallel to the 1969 aftershock zone and at low angle to the regionally inferred greatest horizontal stress. We argue that the microseismically active zone is guided by inherited structures in the basement geology. This and similar structures may represent significant earthquake hazard in plate interiors. [less ▲]

The Use of Spectral Content to Improve Earthquake Early Warning Systems in Central Asia: Case Study of Bishkek, Kyrgyzstan

in Bulletin of the Seismological Society of America (2015), 105(5), 27642773

Toward a loss-driven earthquake early warning and rapid response system for Kyrgyzstan (Central Asia)

in Seismological Research Letters (2014), 85(6), 1328-1340

S-wave velocity images of the Dead Sea Basin provided by ambient seismic noise

in Journal of Asian Earth Sciences (2013), 75

Based on passive seismic interferometry applied to ambient seismic noise recordings between station pairs belonging to a small-scale array, we have obtained shear wave velocity images of the uppermost ... [more ▼]

Based on passive seismic interferometry applied to ambient seismic noise recordings between station pairs belonging to a small-scale array, we have obtained shear wave velocity images of the uppermost materials that make up the Dead Sea Basin. We extracted empirical Green’s functions from cross-correlations of long-term recordings of continuous data, and measured inter-station Rayleigh wave group velocities from the daily correlation functions for positive and negative correlation time lags in the 0.1–0.5 Hz bandwidth. A tomographic inversion of the travel times estimated for each frequency is performed, allowing the laterally varying 3-D surface wave velocity structure below the array to be retrieved. Subsequently, the velocity-frequency curves are inverted to obtain S-wave velocity images of the study area as horizontal depth sections and longitude- and latitude-depth sections. The results, which are consistent with other previous ones, provide clear images of the local seismic velocity structure of the basin. Low shear velocities are dominant at shallow depths above 3.5 km, but even so a spit of land with a depth that does not exceed 4 km is identified as a salt diapir separating the low velocities associated with sedimentary infill on both sides of the Lisan Peninsula. The lack of low speeds at the sampling depth of 11.5 km implies that there are no sediments and therefore that the basement is near 10–11 km depth, but gradually decreasing from south to north. The results also highlight the bowl-shaped basin with poorly consolidated sedimentary materials accumulated in the central part of the basin. The structure of the western margin of the basin evidences a certain asymmetry both whether it is compared to the eastern margin and it is observed in north–south direction. Infill materials down to ∼8 km depth are observed in the hollow of the basin, unlike what happens in the north and south where they are spread beyond the western Dead Sea shore. [less ▲]

First steps toward a reassessment of the seismic risk of the city of Dushanbe (Tajikistan)

in Seismological Research Letters (2013), 84(6), 1026-1038

Shallow lithological structure across the Dead Sea Transform derived from geophysical experiments

in Geochemistry, Geophysics, Geosystems (2011), 12(7),

Lithology classification from seismic tomography: Additional constraints from surface waves

in Journal of African Earth Sciences (2010), 58(3), 547-552

An efficient way of interpreting a seismic profile cross-section is a joint interpretation of velocity models of different types of seismic waves. This study performs tomographic inversion of surface wave ... [more ▼]

An efficient way of interpreting a seismic profile cross-section is a joint interpretation of velocity models of different types of seismic waves. This study performs tomographic inversion of surface wave travel times observed during the seismic profile carried out in Namibia in the framework of the SIMBA project. The thus obtained surface wave velocity model is used to complement the previously computed P- and S-wave models. Profile sections characterised by similar seismic velocities are identified as lithological classes and remapped in model space. Two methods are used to identify such classes: a manual identification of high probability zones in a probability density function, and an automatic neural network approach. The results of these two methods are consistent with each other. The availability of the surface wave velocity model as additional independent physical parameter increases the correlation between the remapped lithological classes and the geological map, leading to the conclusion that the identified classes correspond to real geological formations. [less ▲]

Southern African continental margin: Dynamic processes of a transform margin

in Geochemistry, Geophysics, Geosystems (2009), 10(3),

Dynamic processes at sheared margins associated with the formation of sedimentary basins and marginal ridges are poorly understood. The southern African margin provides an excellent opportunity to ... [more ▼]

Dynamic processes at sheared margins associated with the formation of sedimentary basins and marginal ridges are poorly understood. The southern African margin provides an excellent opportunity to investigate the deep crustal structure of a transform margin and to characterize processes acting at these margins by studying the Agulhas-Falkland Fracture Zone, the Outeniqua Basin, and the Diaz Marginal Ridge. To do this, we present the results of the combined seismic land-sea experiments of the Agulhas-Karoo Geoscience Transect. Detailed velocity-depth models show crustal thicknesses varying from ∼42 km beneath the Cape Fold Belt to ∼28 km beneath the shelf. The Agulhas-Falkland Fracture Zone is embedded in a 50 km wide transitional zone between continental and oceanic crust. The oceanic crust farther south exhibits relatively low average crustal velocities (∼6.0 km/s), which can possibly be attributed to transform-ridge intersection processes and the thermal effects of the adjacent continental crust during its formation. Crustal stretching factors derived from the velocity-depth models imply that extension in the Outeniqua Basin acted on regional as well as more local scales. We highlight evidence for two episodes of crustal stretching. The first, with a stretching factor β of 1.6, is interpreted to have influenced the entire Outeniqua Basin. The stresses possibly originated from the beginning breakup between Africa and Antarctica (∼169–155 Ma). The second episode can be associated with a transtensional component of the shear motion along the Agulhas-Falkland Transform from ∼136 Ma. This episode caused additional crustal stretching with β = 1.3 and is established to only have affected the southern parts of the basin. Crustal velocities directly beneath the Outeniqua Basin are consistent with the interpretation of Cape Supergroup rocks underlying most parts of the basin and the Diaz Marginal Ridge. We propose that the formation of this ridge can be either attributed to a transpressional episode along the Agulhas-Falkland Transform or, more likely, to thermal uplift accompanying the passage of a spreading ridge to the south. [less ▲]