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See detailSouth African speleothems reveal influence of high- and low- latitude forcing over the past 113.5 k.y.
Chase, Brian; Harris, Chris; de Wit, Maarten et al

in Geology (2021), 49(11), 1353-1357

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See detailTaking the Complex Dynamics of Human–Environment–Technology Systems Seriously: A Case Study in Doctoral Education at the University of Luxembourg
König, Ariane UL; Ravetz, Jerome; Raber, Bo Manuel UL et al

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 ▲]

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See detailCan citizen science complement official data sources that serve as evidence-base for policies and practice to improve water quality?
König, Ariane UL; Pickar, Karl Arthur UL; Stankiewicz, Jacek UL et al

in Statistical Journal of the IAOS (2021), 73(1), 189-204

Addressing environmental issues in policy making requires recognising these issues as part of a complex socio-ecological system. The evidence base for such policies and associated monitoring and ... [more ▼]

Addressing environmental issues in policy making requires recognising these issues as part of a complex socio-ecological system. The evidence base for such policies and associated monitoring and implementation measures, as well as related official indicators, statistics and environmental accounts are receiving increasing attention. This paper explores the potential of citizen science as a non-traditional source of data to complement the current data production process for evidence-based policy-making, using pollution of surface waters and its effect on associated ecosystems as an example. The paper develops a framework that helps to explore the official data production process in relation to different purposes of environmental policies. This highlights different challenges that the current official data production process sees itself confronted with in relation to the different purposes of the policies and associated monitoring regimes. These questions are explored with reference to the case of evidence-based policy making on water quality of surface freshwater in the EU, with a focus on Luxembourg. The analysis is based on extensive documentary analysis and literature review, as well as a series of interviews and participatory workshops with various stakeholders, and first results of a pilot project work with engaged citizen volunteers to solicit data on water quality with a focus on its nutrient content. On this basis, this paper argues that citizen science has the clear potential to meaningfully contribute both to the evidence base for policy and practice, as well as to an improved governance process. [less ▲]

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See detailToward a cross-border early-warning system for central Asia
Stankiewicz, Jacek UL; Bindi, D.; Oth, A. et al

in Annals of Geophysics (2015), 58(1),

Rapidly expanding urban areas in Central Asia are increasingly vulnerable to seismic risk; but at present, no earthquake early warning (EEW) systems exist in the region despite their successful ... [more ▼]

Rapidly expanding urban areas in Central Asia are increasingly vulnerable to seismic risk; but at present, no earthquake early warning (EEW) systems exist in the region despite their successful implementation in other earthquake-prone areas. Such systems aim to provide short (seconds to tens of seconds) warnings of impending disaster, enabling the first risk mitigation and damage control steps to be taken. This study presents the feasibility of a large scale cross-border regional system for Central Asian countries. Genetic algorithms are used to design efficient EEW networks, computing optimal station locations and trigger thresholds in recorded ground acceleration. Installation of such systems within 3 years aims to both reducing the endemic lack of strong motion data in Central Asia that is limiting the possibility of improving seismic hazard assessment, and at providing the first regional earthquake early warning system in the area [less ▲]

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See detailMicroseismic Activity and Basement Controls on an Active Intraplate Strike-Slip Fault, Ceres–Tulbagh, South Africa
Smit, Louis; Fagereng, Ake; Braeuer, Benjamin et al

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 ▲]

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See detailThe Use of Spectral Content to Improve Earthquake Early Warning Systems in Central Asia: Case Study of Bishkek, Kyrgyzstan
Stankiewicz, Jacek UL; Bindi, Dino; Oth, Adrien et al

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

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See detailOn-site early-warning system for bishkek (Kyrgyzstan)
Bindi, D.; Boxberger, T.; Orunbaev, S. et al

in Annals of Geophysics (2015), 58(1),

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See detailToward a loss-driven earthquake early warning and rapid response system for Kyrgyzstan (Central Asia)
Pittore, M.; Bindi, D.; Stankiewicz, Jacek UL et al

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

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See detail3.5billion years of reshaped Moho, southern Africa
Stankiewicz, Jacek UL; De Wit, M.

in Tectonophysics (2013), 609

According to some previous studies, Archean continental crust is, on global average, apparently thinner than Proterozoic crust. Subsequently, the validity of this statement has been questioned. To provide ... [more ▼]

According to some previous studies, Archean continental crust is, on global average, apparently thinner than Proterozoic crust. Subsequently, the validity of this statement has been questioned. To provide an additional perspective on this issue, we present analyses of Moho signatures derived from recent seismic data along swaths 2000 km in length across southern Africa and its flanking ocean. The imaged crust has a near continuous age range between ca. 0.1 and 3.7 billion years, and the seismic data allow direct comparison of Moho depths between adjacent Archean, Proterozoic and Phanerozoic crust. We find no simple secular change in depth to Moho over this time period. In contrast, there is significant variation in depth to Moho beneath both Archean and Proterozoic crust; Archean crust of southern Africa displays as much crustal diversity in thickness as the adjacent Proterozoic crust. The Moho beneath all crustal provinces that we have analysed has been severely altered by tectono-metamorphic and igneous processes, in many cases more than once, and cannot provide unequivocal data for geodynamic models dealing with secular changes in continental crust formation. These results and conclusions are similar to those documented along ca. 2000 km swaths across the Canadian Shield recorded by Lithoprobe. Tying the age and character of the Precambrian crust of southern Africa to their depth diversities is clearly related to manifold processes of tectono-thermal ‘surgery’ subsequent to their origin, the details of which are still to be resolved, as they are in most Precambrian terranes. Reconstructing pristine Moho of the early Earth therefore remains a formidable challenge. In South Africa, better knowledge of ‘fossilised’ Archean crustal sections ‘turned on-edge’, such as at the Vredefort impact crater (for the continental crust), and from the Barberton greenstone belt (for oceanic crust) is needed to characterize potential pristine Archean Moho transitions. [less ▲]

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See detailFirst steps toward a reassessment of the seismic risk of the city of Dushanbe (Tajikistan)
Pilz, M.; Bindi, D.; Boxberger, T. et al

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

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See detailDesigning efficient earthquake early warning systems: Case study of Almaty, Kazakhstan
Stankiewicz, Jacek UL; Bindi, D.; Oth, A. et al

in Journal of Seismology (2013), 17(4), 1125-1137

Rapidly expanding urban areas in Central Asia are increasingly vulnerable to seismic risk; but at present, no earthquake early warning (EEW) systems exist in the region despite their successful ... [more ▼]

Rapidly expanding urban areas in Central Asia are increasingly vulnerable to seismic risk; but at present, no earthquake early warning (EEW) systems exist in the region despite their successful implementation in other earthquake-prone areas. Such systems aim to provide short (seconds to tens of seconds) warnings of impending disaster, enabling the first risk mitigation and damage control steps to be taken. This study presents the feasibility of such a system for Almaty, Kazakhstan. Genetic algorithms are used to design efficient EEW networks, computing optimal station locations and trigger thresholds in recorded ground acceleration. Factors like the possibility of station failure, elevation and access difficulty to a potential site, and the potential usefulness of existing stations in the region are considered. We present a large set of possible efficient networks, to which further selection criteria can be applied by both the installation teams and the end user, such as authorities in Almaty. [less ▲]

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See detailS-wave velocity images of the Dead Sea Basin provided by ambient seismic noise
Badal, J.; Chen, Y.; Chourak, M. et al

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 ▲]

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See detailDead sea basin imaged by ambient seismic noise tomography
Stankiewicz, Jacek UL; Weber, M. H.; Mohsen, A. et al

in Pure and Applied Geophysics (2012), 169(4), 615-623

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See detailShallow lithological structure across the Dead Sea Transform derived from geophysical experiments
Stankiewicz, Jacek UL; Muñoz, G.; Ritter, O. et al

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

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See detailShallow structure in the Karoo Basin, South Africa, inferred from a near vertical reflection seismic profile
Stankiewicz, Jacek UL

in South African Journal of Geology (2011), 114(3-4), 293-298

A Near Vertical Reflection seismic profile from Beaufort West to Klaarstroom was carried out using controlled source vibroseis sweeps and a rolling spread of recording geophones. Arrivals of refracted P ... [more ▼]

A Near Vertical Reflection seismic profile from Beaufort West to Klaarstroom was carried out using controlled source vibroseis sweeps and a rolling spread of recording geophones. Arrivals of refracted P- and S-waves generated in the sweeps were manually picked. 2-D travel time tomography was used to compute P-wave and S-wave velocity variations for depths down to ~300 m beneath the profile. Checkerboard tests illustrate the resolution of the velocity models. A probabilistic classification approach was used in an attempt to identify lithological classes based on observed P- and S-wave velocities. Two classes were identified, but they do not correspond to different geological formations. Thus the variations of seismic velocities due to pressure and compaction are greater inside a given formation than between different formations. The subsurface down to a depth of 50 to 100 metres shows very little variation in S-wave velocity, 2.2 ± 0.1 km/s, irrespective of the underlying geological formation. Directly below this zone variations in P- and S-wave velocities are observed, where the Vp/Vs ratio is approximately 2. Care must thus be taken when attempting to classify lithologies using statistical distribution of geophysical parameters – systematic variations inside a single geological unit can be more significant than between separate geological formations [less ▲]

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See detailLithology classification from seismic tomography: Additional constraints from surface waves
Stankiewicz, Jacek UL; Bauer, K.; Ryberg, T.

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 ▲]

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See detailLake Toba volcano magma chamber imaged by ambient seismic noise tomography
Stankiewicz, Jacek UL; Ryberg, T.; Haberland, C. et al

in Geophysical Research Letters (2010), 37(17),

For the first time, ambient noise tomography is used to clearly image the magma chamber beneath Lake Toba caldera, one of the largest Quaternary calderas on Earth. Using data from 40 seismic stations ... [more ▼]

For the first time, ambient noise tomography is used to clearly image the magma chamber beneath Lake Toba caldera, one of the largest Quaternary calderas on Earth. Using data from 40 seismic stations deployed between May and October 2008 around Lake Toba, empirical Green’s functions are extracted from long term cross‐correlations of continuous records. These functions are dominated by Rayleigh waves, whose group velocities can be measured in the period range from 2.5 to 12 seconds. Arrival times of these waves are picked for a given period and inverted using 2‐D tomography to calculate lateral variations in velocity for the given period. This was done for six different periods, which all correspond to different sampling depths. Thus the six 2‐D models presented together provide information on velocity variations with depth. The results show a low‐velocity body coincident with the Lake Toba caldera, representing the magma chamber under the volcano. The chamber is observed to have a complex 3‐D geometry, with at least two separate sub‐chambers underlying the caldera. Other results include a deep low velocity body, possibly another magma chamber, south west of the lake with an upper limit of ∼7 km depth. The maximum depth to which this body reaches could not be resolved. The Sumatra Fault marks a velocity contrast, but only down to depths not greater than 5 km. The reliability of the results was further confirmed by checkerboard recovery tests. [less ▲]

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See detailSouthern African continental margin: Dynamic processes of a transform margin
Parsiegla, N.; Stankiewicz, Jacek UL; Gohl, K. et al

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 ▲]

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See detailSimple models for the Beattie Magnetic Anomaly in South Africa
Quesnel, Y.; Weckmann, U.; Ritter, O. et al

in Tectonophysics (2009), 478(1-2), 111-118

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See detailRestoring pan-African-Brasiliano connections: More Gondwana control, less Trans-Atlantic corruption
De Wit, M. J.; Stankiewicz, Jacek UL; Reeves, C.

in Geological Society Special Publication (2008), 294

The concept of South America and Africa as rigid continents during the formation, growth and motion of their respective plates has frustrated reconstruction of a tight, geologically economic fit between ... [more ▼]

The concept of South America and Africa as rigid continents during the formation, growth and motion of their respective plates has frustrated reconstruction of a tight, geologically economic fit between these two fragments in their Gondwana framework. We recognize that (1) internal strains released during and following Gondwana break-up have distorted their actual shapes within Gondwana and (2) these two continents comprise mosaics of smaller microblocks, or platelets, of relatively undistorted Precambrian terrains that experienced modest, episodic relative motions along rift zones that separate them. This permits a fresh approach to quantitative reconstructions of palaeo-continents. Former geological ties forged at the time of Gondwana amalgamation, now exposed at the continental margins of the South Atlantic as piercing points, provide robust anchors for new paleo-cartographic experiments. We present two new tectonic maps of the Brasiliano and Pan-African structures of West Gondwana on which we identify ten piercing points that, if re-joined simultaneously, could facilitate quantification of a well-substantiated Gondwana fit and help retrace the evolution of its continental margins with greater accuracy than has been achieved until now. This has significant bearing on understanding the origin and evolution of passive continental margins, and the geodynamics of Gondwana break-up. [less ▲]

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