Submarine paleoseismology of the northern Hikurangi subduction margin of New Zealand as deduced from Turbidite record since 16 ka

International audiencePaleoseismic studies seek to characterise the signature of pre-historical earthquakes by deriving quantitative information from the geological record such as the source, magnitude and recurrence of moderate to large earthquakes. In this study, we provide a w16,000 yr-long paleo-earthquake record of the 200 km-long northern Hikurangi Margin, New Zealand, using cm-thick deep-sea turbidites identified in sediment cores. Cores were collected in strategic locations across the margin within three distinct morphological re-entrants e the Poverty, Ruatoria and Matakaoa re-entrants. The turbidite facies vary from muddy to sandy with evidence for rare hyperpycnites interbedded with hemipelagites and tephra. We use the Oxal probabilistic software to model the age of each turbidite, using the sedimentation rate of hemipelagite deduced from well-dated tephra layers and radiocarbon ages measurements on planktonic foraminifera. Turbidites are correlated from one core to the other using similarity in sedimentary facies, petrophysical properties and ages. Results show that 46 turbidites are synchronous along the entire margin. Amongst them 41 are interpreted as originating from the upper continental slope in response to earthquake-triggered slope failures between 390 170 to 16,450 310 yr BP. Using well-established empirical relationships that combine peak ground acceleration, magnitude and location of earthquakes, we calculate that synchronous slope failures were triggered by the rupture of 3 of the 26 known active faults in the region, each capable of generating Mw 7.3 to 8.4 earthquakes e two are crustal reverse faults and one is the subduction interface. The 41 Mw 7.3 earthquakes occurred at an average recurrence interval of w400 yr over the last w16,000 yr. Among them, twenty are interpreted as subduction interface earthquakes that occurred at an average recurrence interval of w800 yr, with alternating periods of high activity and low return times (305e610 yr) and quiescence periods with high return times (1480e2650 yr). Based on turbidite paleoseismology, we propose that subduction interface earthquakes were of lower magnitude during active periods (Mw > 7.5) than during quiescence periods (Mw 8.2)

Building an 18 000-year-long paleo-earthquake record from detailed deep-sea turbidite characterisation in Poverty Bay, New Zealand

In :" Marine and lake paleoseismology" Special Issue. Editor(s) : D. Pantosti, E. Gràcia, G. Lamarche, and H. NelsonInternational audienceTwo 20 m-long sedimentary cores collected in two neighbouring mid-slope basins of the Paritu Turbidite System in Poverty Bay, east of New Zealand, show a high concentration of turbidites (5 to 6 turbidites per meter), interlaid with hemipelagites, tephras and a few debrites. Turbidites occur as both stacked and single, and exhibit a range of facies from muddy to sandy turbidites. The age of each turbidite is estimated using the statistical approach developed in the OxCal software from an exceptionally dense set of tephrochronology and radiocarbon ages ( 1 age per meter). The age, together with the facies and the petrophysical properties of the sediment (density, magnetic susceptibility and Pwave velocity), allows the correlation of turbidites across the continental slope (1400-2300m water depth). We identify 73 synchronous turbidites, named basin events, across the two cores between 819±191 and 17 729±701 yr BP. Compositional, foraminiferal and geochemical signatures of the turbidites are used to characterise the source area of the sediment, the origin of the turbidity currents, and their triggering mechanism. Sixty-seven basin events are interpreted as originated from slope failures on the upper continental slope in water depth ranging from 150 to 1200 m. Their earthquake trigger is inferred from the heavily gullied morphology of the source area and the water depth at which slope failures originated. We derive an earthquake mean return time of 230 yr, with a 90% probability range from 10 to 570 yr. The earthquake chronology indicates cycles of progressive decrease of earthquake return times from 400 yr to 150 yr at 0- 7 kyr, 8.2-13.5 kyr, 14.7-18 kyr. The two 1.2 kyr-long intervals in between (7-8.2 kyr and 13.5-14.7 kyr) correspond to basin-wide reorganisations with anomalous turbidite deposition (finer deposits and/or non deposition) reflecting the emplacement of two large mass transport deposits much more voluminous than the "classical" earthquake-triggered turbidites. Our results show that the progressive characterisation of a turbidite record from a single sedimentary system can provide a continuous paleo-earthquake history in regions of short historical record and incomplete onland paleoearthquake evidences. The systematic description of each turbidite enables us to infer the triggering mechanism

Exon Domesday : méthodes numériques appliquées à la codicologie pour l’étude d’un manuscrit anglo-normand

Dans cet article, nous présentons une analyse méthodologique de l’étude de l’Exon Domesday Book, Exeter, Cathedral Library, ms 3500. L’Exon Domesday contient la documentation relative au sud-ouest de l’Angleterre, compilée au cours de l’enquête Domesday, puis retravaillée dans le Great Domesday Book, tel que nous le connaissons aujourd’hui. L’Exon Domesday offre donc un point de vue unique sur les méthodes de travail des premiers anglo-normands, nous fournissant des témoignages essentiels de ce qu’ils ont fait, comment ils l’ont fait, et probablement aussi pourquoi. Cependant, le manuscrit est extrêmement complexe, car il est le fruit du travail d’une équipe de scribes qui travaillent ensemble dans des délais très serrés. Sa structure est très irrégulière, étant formé de cahiers allant d’un bifeuillet, ou même d’un feuillet dépareillé, jusqu’à un cahier de vingt feuillets. Afin de comprendre le manuscrit et sa fabrication, nous avons donc développé des outils et des méthodes numériques et pour aider à visualiser et analyser sa structure. Bien qu’ils soient fermement ancrés dans les problématiques du projet, ces outils sont également fondés sur des principes de codicologie qui, à notre avis, peuvent s’appliquer beaucoup plus largement au-delà de ce projet particulier.In this article, we present a methodological discussion of a study of the Exon Domesday Book, Exeter, Cathedral Library, ms 3500. Exon Domesday contains records for the south-west of England which were compiled for the Domesday survey and then reworked into Great Domesday Book as we know it today. Exon Domesday therefore provides a unique view into the workings of the early Anglo-Normans, providing us with crucial evidence of what they did, how and probably also why. However, the manuscript is extremely complex, being the work of a team of scribes working together under significant pressures of time. It is very irregular in composition, with quires ranging from one bifolium or even a singleton to those of twenty leaves. In order to understand the manuscript and its production, we have developed digital tools and approaches to help visualise and analyse the structure. Although they are based firmly in the research questions of the project, they are also founded on principles of codicology that we believe are applicable much more widely than just this project.In questo articolo presentiamo una discussione metodologica relativa allo studio del manoscritto Exon Domesday Book, Exeter, Cathedral Library, ms 3500. L’Exon Domesday contiene documenti relativi al sud-ovest dell'Inghilterra compilati nel corso dell’inchiesta relativa alla compilazione del Domesday Book e poi rielaborati nel Great Domesday Book come lo conosciamo oggi. L’Exon Domesday fornisce quindi una visione unica del funzionamento dei primi anni di dominio anglo-normanno, fornendoci le prove cruciali di ciò che hanno fatto, ma anche di come lo hanno fatto e probabilmente del perché. Tuttavia, il manoscritto è estremamente complesso, trattandosi del lavoro di un gruppo di copisti che lavoravano insieme con tempi di realizzazione molto stretti. La struttura del manoscritto è molto irregolare, con fascicoli che vanno dal bifolio o anche composti di una carta isolata, fino a fascicoli di venti fogli. Per comprendere il manoscritto e la sua fabbricazione, sono stati sviluppati strumenti e approcci digitali che aiutano a visualizzarne e analizzarne la struttura. Anche se tali strumenti sono stati concepiti per rispondere alle questioni di ricerca specifiche del progetto, questi si basano anche su principi di codicologia che riteniamo applicabili ampiamente

Postglacial (after 18 ka) deep-sea sedimentation along the Hikurangi subduction margin (New Zealand): Characterisation, timing and origin of turbidites

International audienceRecent sedimentation along the Hikurangi subduction margin off northeastern New Zealand is investigated using a series of piston cores collected between 2003 and 2008. The active Hikurangi Margin lies along the Pacific-Australia subduction plate boundary and contains a diverse range of geomorphologic settings. Slope basin stratigraphy is thick and complex, resulting from sustained high rates of sedimentation from adjacent muddy rivers throughout the Quaternary. Turbidites deposited since c. 18 ka in the Poverty, Ruatoria and Matakaoa re-entrants are central to this study in that they provide a detailed record of the past climatic conditions and tectonic activity. Here, alternating hemipelagite, turbidite, debrite and tephra layers reflect distinctive depositional modes of marine sedimentation, turbidity current, debris flow and volcanic eruption, respectively. Turbidites dominate the record, ranging in lithofacies from muddy to sandy turbidites, and include some basal-reverse graded turbidites inferred to be derived from hyperpycnal flows. Stacked turbidites are common and indicate multiple gravity-flows over short time periods. The chronology of turbidites is determined by collating an extremely dense set of radiocarbon ages and dated tephra, which facilitate sedimentation rate calculation and identification of the origin of turbidites. Sedimentation rates range from 285 cm/ka during late glacial time (18.5-17 ka) to 15 to 109 cm/ka during postglacial time (17-0 ka). Turbidite deposition is controlled by: (1) the emplacement of slope avalanches reorganising sediment pathways; (2) the postglacial marine transgression leading to a five-fold reduction in sediment supply to the slope due to disconnection of river mouths from the shelf edge, and (3) the Holocene/ Pleistocene boundary climate warming resulting in a drastic decrease in the average turbidite grain-size. Flood-induced turbidites are scarce: nine hyperpycnites are recognised since 18 ka and the youngest is correlated to the largest ENSO-related storm event recorded onland (Lake Tutira). Other turbidites contain a benthic foraminiferal assemblage which is strictly reworked from the upper slope and which relates to large earthquakes over the last c. 7 ka. They yield a shorter return time (270-430 years) than the published coastal records for large earthquakes (c. 670 years), but the offshore record is likely to be more complete. The deep-sea sedimentation along the New Zealand active margin illustrates the complex interaction of tectonic and climate in turbidite generation. Climate warming and glacio-eustatic fluctuations are well recorded at a millennial timescale (18 ka), while tectonic deformation and earthquakes appear predominant in fostering turbidite production at a centennial timescale (270-430 years)

Global Health Values of a Multidirectional Near Peer Training Program in Surgery, Pathology, Anatomy, Research Methodology, and Medical Education for Haitian, Rwandan, and Canadian Medical Students

Background: As health care delivery increasingly requires providers to cross international borders, medical students at McGill University, Canada, developed a multidirectional exchange program with Haiti and Rwanda. The program integrates surgery, pathology, anatomy, research methodology, and medical education. Objective: The aim of the present study was to explore the global health value of this international training program to improve medical education within the environment of developing countries, such as Haiti and Rwanda, while improving sociocultural learning of Canadian students. Methods: Students from the University of Kigali, Rwanda and Université Quisqueya, Haiti, participated in a 3-week program at McGill University. The students spanned from the first to sixth year of their respective medical training. The program consisted of anatomy dissections, surgical simulations, clinical pathology shadowing, and interactive sessions in research methodology and medical education. To evaluate the program, a survey was administered to students using a mixed methodology approach. Findings: Common benefits pointed out by the participants included personal and professional growth. The exchange improved career development, sense of responsibility toward one’s own community, teaching skills, and sociocultural awareness. The participants all agreed that the anatomy dissections improved their knowledge of anatomy and would make them more comfortable teaching the material when the returned to their university. The clinical simulation activities and shadowing experiences allowed them to integrate the different disciplines. However, the students all felt the research component had too little time devoted to it and that the knowledge presented was beyond their educational level. Conclusion: The development of an integrated international program in surgery, pathology, anatomy, research methodology, and medical education provided medical students with an opportunity to learn about differences in health care and medical education between the 3 countries. This exchange demonstrated that a crosscultural near-peer teaching environment can be an effective and sustainable method of medical student-centered development in global health

Contribution des sols à la production de services écosystémiques en milieu urbain – une revue

Les sols fournissent des services à la population humaine, appelés services écosystémiques. En vue de répondre aux problématiques environnementales qui se concentrent en milieu urbain, il est attendu que ces services soient facilement appréhendables par les acteurs de l’aménagement. Cet article propose des définitions claires de termes centraux comme « sol urbain », « sol anthropisé » et « couverture de sol » ; il présente également les caractéristiques bio-physico-chimiques des sols urbains. Des analyses bibliométrique et bibliographique de la littérature scientifique sur les services écosystémiques des sols urbains permettent de positionner la place de ce sujet sur les 20 dernières années et de proposer une liste de ces services. Enfin, une analyse critique des perspectives de développement d’outils d’aide à la décision à l’attention des aménageurs pour la prise en compte des sols urbains à chaque étape de l’aménagement est proposée.Soils, as ecosystems provide services that are also called ecosystem services. In the context of natural resources preservation, urban soils are expected to be multifunctional and to provide high level of ecosystem services (e.g. vegetation support, building support, flood control). Therefore, there is a need for urban planners to take into account the urban soil potentials in urban project development. This article proposes definitions of such crucial terms such as “urban soil”, “anthropized soil” and “sol cover”; it also presents the main bio-physical-chemical characteristics of urban soils. A bibliometric analysis has been conducted to describe the position of ecosystem services provided by urban soils within the frame of actual research. A list and a description of the ecosystem services provided by urban soils is proposed. Finally, this article offers prospects for the development of decision-making tools for planners to encourage them to take into account soil ecosystem at each stage of planning

Internal states of model isotropic granular packings. III. Elastic properties

In this third and final paper of a series, elastic properties of numerically simulated isotropic packings of spherical beads assembled by different procedures and subjected to a varying confining pressure P are investigated. In addition P, which determines the stiffness of contacts by Hertz's law, elastic moduli are chiefly sensitive to the coordination number, the possible values of which are not necessarily correlated with the density. Comparisons of numerical and experimental results for glass beads in the 10kPa-10MPa range reveal similar differences between dry samples compacted by vibrations and lubricated packings. The greater stiffness of the latter, in spite of their lower density, can hence be attributed to a larger coordination number. Voigt and Reuss bounds bracket bulk modulus B accurately, but simple estimation schemes fail for shear modulus G, especially in poorly coordinated configurations under low P. Tenuous, fragile networks respond differently to changes in load direction, as compared to load intensity. The shear modulus, in poorly coordinated packings, tends to vary proportionally to the degree of force indeterminacy per unit volume. The elastic range extends to small strain intervals, in agreement with experimental observations. The origins of nonelastic response are discussed. We conclude that elastic moduli provide access to mechanically important information about coordination numbers, which escape direct measurement techniques, and indicate further perspectives.Comment: Published in Physical Review E 25 page

Alternatives to Student Outbound Mobility-Improving Students' Cultural Competency Skills Online to Improve Global Health Without Travel.

INTRODUCTION: Student outbound mobility is a major element in internationalization of medical education and global health education. However, this approach is often criticized, as it is inherently inequitable. Internationalization at home is a newer concept that aims to provide students with international skills and experiences without exchange travel. We report detailed outcomes of an international online program during the COVID-19 pandemic, which aimed to include acquisition of cultural awareness and competency-similar to what the students would have obtained if they had travelled abroad. METHOD: Sixty-eight students from 12 international universities participated in international small peer group collaborative work, and online networking. Perceived improvement of cultural competency using Likert scale and open-ended questions was used as a measure of success. Furthermore, students' definition of cultural competency in the different countries was obtained. RESULTS: Students improved their cultural competency skills. Data analysis supported statistically significant improvement of the above skills after the program, in comparison to the start of the program. DISCUSSION: Internationalization of medical education can be achieved at home-via structured online peer exchanges-and can provide students with intercultural skills and networking opportunities that are typically achieved via international in-person travel. The above represents a socially just and equitable way to reach all students and can result in improvement of their cultural competency, preparing them for their work in global health, and thereby resulting in improvement of global health. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40670-021-01332-9