Contrasting volcanic-tectonic processes during the past 2 Ma on the Mid-Atlantic Ridge: submersible mapping,petrological and magnetic results at lat. 34°52′ N and 33°55′ N

In August–September of 1995, 20 Nautile dives and detailed magnetic surveys (spaced every 1.8 km) were undertaken on two segments of the Mid-Atlantic Ridge between the Oceanographer and Hayes fractures zones. These two segments are only 65 km apart and show strong morphology and gravity contrasts. OH1 is shallower and has a large mantle Bouguer anomaly (MBA) bull's eye, whereas OH3 is deeper and has a smaller MBA bull's eye.Thirteen dives were devoted to segment OH1. The Median Ridge (MR) located on the central high (1700 m deep) is topped by 100 to 300 m high circular volcanoes. The volcanics consists mainly of porphyritic and/or vesicular pillows and volcaniclastics. The NVZ (2200 m deep), located in the valley floor east of the MR, consists of near aphyric fluid lava flows. A chain of off-axis volcanoes, displaying a magnetic continuity with surroundings, extends on both sides of the axis. Three volcanoes on the east side and one on the west side of the axis were explored and sampled by submersible. The off-axis increase of weathering, Fe-Mn coating and magnetic signature suggest that the volcanoes were built at or near the ridge axis. The spacing of NS elongated hills bearing circular volcanoes and separated large magnetic signature (2 to 4 km) depressions suggests that several similar volcanic events occured during the past 2 Ma. The last 1 Ma episode involves (1) the construction of an axial ridge (MR) by fissure eruptions and the formation of circular summit volcanoes by focused volcanism, and (2) the extrusion of fluid magma in the depressions formed by further fissuring and faulting of the MR.     

Application-driven ground motion prediction equation for seismic hazard assessments in non-cratonic moderate-seismicity areas

We present a ground motion prediction equation (GMPE) for probabilistic seismic hazard assessments (PSHA) in low-to-moderate seismicity areas, such as Germany. Starting from the NGA-West2 flat-file (Ancheta et al. in Earthquake Spectra 30:989–1005, 2014), we develop a model tailored to the hazard application in terms of data selection and implemented functional form. In light of such hazard application, the GMPE is derived for hypocentral distance (along with the Joyner-Boore one), selecting recordings at sites with vs30 ≥ 360 m/s, distances within 300 km, and magnitudes in the range 3 to 8 (being 7.4 the maximum magnitude for the PSHA in the target area). Moreover, the complexity of the considered functional form is reflecting the availability of information in the target area. The median predictions are compared with those from the NGA-West2 models and with one recent European model, using the Sammon’s map constructed for different scenarios. Despite the simplification in the functional form, the assessed epistemic uncertainty in the GMPE median is of the order of those affecting the NGA-West2 models for the magnitude range of interest of the hazard application. On the other hand, the simplification of the functional form led to an increment of the apparent aleatory variability. In conclusion, the GMPE developed in this study is tailored to the needs for applications in low-to-moderate seismic areas and for short return periods (e.g., 475 years); its application in studies where the hazard is involving magnitudes above 7.4 and for long return periods is not advised.     

Influence of microclimate and geomorphological factors on alpine vegetation in the Western Swiss Alps

Among the numerous environmental factors affecting plant communities in alpine ecosystems, the influence of geomorphic processes and landforms has been minimally investigated. Subjected to persistent climate warming, it is vital to understand how these factors affect vegetation properties. Here, we studied 72 vegetation plots across three sites located in the Western Swiss Alps, characterized by high geomorphological variability and plant diversity. For each plot, vascular plant species were inventoried and ground surface temperature, soil moisture, topographic variables, earth surface processes (ESPs) and landform morphodynamics were assessed. The relationships between plant communities and environmental variables were analysed using non-metric multi-dimensional scaling (NMDS) and multivariate regression techniques (generalized linear model, GLM, and generalized additive model, GAM). Landform morphodynamics, growing degree days (sum of degree days above 5°C) and mean ground surface temperature were the most important explanatory variables of plant community composition. Furthermore, the regression models for species cover and species richness were significantly improved by adding a morphodynamics variable. This study provides complementary support that landform morphodynamics is a key factor, combined with growing degree days, to explain alpine plant distribution and community composition. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.     

Comparing Eulerian and Lagrangian eddy census for a tide-less,semi-enclosed basin,the Baltic Sea

Ocean Dynamics - Eddies in the global and coastal ocean play a key role in mixing and transport processes. Here, we present an eddy census for the Baltic Sea covering the years 2008–2010. The...     

Subsidies to high seas bottom trawl fleets and the sustainability of deep-sea demersal fish stocks

The life spans of demersal species of fishes occurring in deep-waters are much longer and their potential growth rates much lower than those of related shallow water species. As a result, deep-sea demersal fish species are more vulnerable to exploitation. This is because low growth rates relative to the available market discount rate for capital makes it desirable for fishing firms to mine, rather than sustainably exploit, these resources even in the absence of fisheries subsidies. However, it is common knowledge that governments around the world do provide subsidies to their fishing industries. The objective of this contribution is to estimate the global amount of subsidies paid to bottom trawl fleets operating in the high seas, i.e., outside of the Exclusive Economic Zones of maritime countries. Our study suggests that fisheries subsidies to these fleets stand at about US$152 million per year, which constitutes 25% of the total landed value of the fleet. Economic data for bottom trawlers suggest that the profit achieved by this vessel group is normally not more than 10% of landed value. The implication of this finding is that without subsidies, the bulk of the world's bottom trawl fleet operating in the high seas will be operating at a loss, and unable to fish, thereby reducing the current threat to deep-sea and high seas fish stocks.     

Why did a vehicle stop? A methodology for detection and classification of stops in vehicle trajectories

ABSTRACT

Trajectory data mining is a lively research field in the domain of spatio-temporal data mining. Trajectory pattern mining comprises a set of specific pattern mining methods, which are applied as consecutive steps on a trajectory with the goal to extract and classify re-occurring spatio-temporal patterns. Despite the common nature and frequent usage of such methods by the GIScience community, a methodological approach is missing so far, especially when it comes to the use of machine learning-based classification methods. The current work closes this gap by proposing and evaluating a machine learning-based 3-steps trajectory data mining methodology using the detection and classification of stop points in vehicle trajectories as example. The work describes in detail the applied methodologies with respect to the three mining steps ‘stop detection’, ‘feature extraction’ and ‘classification in traffic-relevant and non-traffic-relevant stops’ and evaluates six machine learning-based classification algorithms using a real-world dataset of 15,498 vehicle trajectories with 5,899 detected stops (thereof 2,032 manually classified). Due to its exemplary nature, the presented methodology is suited to act as blueprint for similar trajectory data mining problems.     

Assessing impacts of agricultural water interventions in the Kothapally watershed,Southern India

The paper describes a hydrological model for agricultural water intervention in a community watershed at Kothapally in India, developed through integrated management and a consortium approach. The impacts of various soil and water management interventions in the watershed are compared to no‐intervention during a 30‐year simulation period by application of the calibrated and validated ARCSWAT 2005 (Version 2.1.4a) modelling tool. Kothapally receives, on average, 800 mm rainfall in the monsoon period. 72% of total rainfall is converted as evaporation and transpiration (ET), 20% is stored by groundwater aquifer, and 8% exported as outflow from the watershed boundary in current water interventions. ET, groundwater recharge and outflow under no‐intervention conditions are found to be 64, 9, and 19%, respectively. Check dams helped in storing water for groundwater recharge, which can be used for irrigation, as well minimising soil loss. In situ water management practices improved the infiltration capacity and water holding capacity of the soil, which resulted in increased water availability by 10–30% and better crop yields compared to no‐intervention. Water outflows from the developed watershed were more than halved compared to no‐intervention, indicating potentially large negative downstream impacts if these systems were to be implemented on a larger scale. On the other hand, in the watershed development program, sediment loads to the streams were less than one‐tenth. It can be concluded that the hydrological impacts of large‐scale implementation of agricultural water interventions are significant. They result in improved rain‐fed agriculture and improved productivity and livelihood of farmers in upland areas while also addressing the issues of poverty, equity, and gender in watersheds. There is a need for case‐specific studies of such hydrological impacts along with other impacts in terms of equity, gender, sustainability, and development at the mesoscale. Copyright © 2011 John Wiley & Sons, Ltd.     

Estimation of crack opening from a two‐dimensional continuum‐based finite element computation

Damage models are capable of representing crack initiation and mimicking crack propagation within a continuum framework. Thus, in principle, they do not describe crack openings. In durability analyses of concrete structures however, transfer properties are a key issue controlled by crack propagation and crack opening. We extend here a one‐dimensional approach for estimating a crack opening from a continuum‐based finite element calculation to two‐dimensional cases. The technique operates in the case of mode I cracking described in a continuum setting by a nonlocal isotropic damage model. We used the global tracking method to compute the idealized crack location as a post‐treatment procedure. The original one‐dimensional problem devised in Dufour et al. [4] is recovered as profiles of deformation orthogonal to the idealized crack direction are computed. An estimate of the crack opening and an error indicator are computed by comparing finite element deformation profiles and theoretical profiles corresponding to a displacement discontinuity. Two estimates have been considered: In the strong approach, the maxima of the profiles are assumed to be equal; in the weak approach, the integrals of each profile are set equal. Two‐dimensional numerical calculations show that the weak estimates perform better than do the strong ones. Error indicators, defined as the distance between the numerical and theoretical profiles, are less than a few percentages. In the case of a three‐point bending, test results are in good agreement with experimental data, with an error lower than 10% for widely opened crack (> 40µm). Copyright © 2011 John Wiley & Sons, Ltd.     

The transition from complex crater to peak-ring basin on Mercury: New observations from MESSENGER flyby data and constraints on basin formation models

The study of peak-ring basins and other impact crater morphologies transitional between complex craters and multi-ring basins is important to our understanding of the mechanisms for basin formation on the terrestrial planets. Mercury has the largest population, and the largest population per area, of peak-ring basins and protobasins in the inner solar system and thus provides important data for examining questions surrounding peak-ring basin formation. New flyby images from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft have more than doubled the area of Mercury viewed at close range, providing nearly complete global coverage of the planet's surface when combined with flyby data from Mariner 10. We use this new near-global dataset to compile a catalog of peak-ring basins and protobasins on Mercury, including measurements of the diameters of the basin rim crest, interior ring, and central peak (if present). Our catalog increases the population of peak-ring basins by ∼150% and protobasins by ∼100% over previous catalogs, including 44 newly identified peak-ring basins (total=74) and 17 newly identified protobasins (total=32). A newly defined transitional basin type, the ringed peak-cluster basin (total=9), is also described. The new basin catalog confirms that Mercury has the largest population of peak-ring basins of the terrestrial planets and also places the onset rim-crest diameter for peak-ring basins at , which is intermediate between the onset diameter for peak-ring basins on the Moon and those for the other terrestrial planets. The ratios of ring diameter to rim-crest diameter further emphasize that protobasins and peak-ring basins are parts of a continuum of basin morphologies relating to their processes of formation, in contrast to previous views that these forms are distinct. Comparisons of the predictions of peak-ring basin-formation models with the characteristics of the basin catalog for Mercury suggest that formation and modification of an interior melt cavity and nonlinear scaling of impact melt volume with crater diameter provide important controls on the development of peak rings. The relationship between impact-melt production and peak-ring formation is strengthened further by agreement between power laws fit to ratios of ring diameter to rim-crest diameter for peak-ring basins and protobasins and the power-law relation between the dimension of a melt cavity and the crater diameter. More detailed examination of Mercury's peak-ring basins awaits the planned insertion of the MESSENGER spacecraft into orbit about Mercury in 2011.