Parametrizing surface wave tomographic models with harmonic spherical splines

We present a mathematical framework and a new methodology for the parametrization of surface wave phase-speed models, based on traveltime data. Our method is neither purely local, like block-based approaches, nor is it purely global, like those based on spherical harmonic basis functions. Rather, it combines the well-known theory and practical utility of the spherical harmonics with the spatial localization properties of spline basis functions. We derive the theoretical foundations for the application of harmonic spherical splines to surface wave tomography and summarize the results of numerous numerical tests illustrating the performance of a practical inversion scheme based upon them. Our presentation is based on the notion of reproducing-kernel Hilbert spaces, which lends itself to the parametrization of fully 3-D tomographic earth models that include body waves as well.     

Tidal tails in cold dark matter cosmologies

We study the formation of tidal tails in pairs of merging disc galaxies with structural properties motivated by current theories of cold dark matter (CDM) cosmologies. In a recent study, Dubinski, Mihos & Hernquist showed that the formation of prominent tidal tails can be strongly suppressed by massive and extended dark haloes. For the large halo-to-disc mass ratio expected in CDM cosmologies their sequence of models failed to produce strong tails like those observed in many well-known pairs of interacting galaxies. In order to test whether this effect can constrain the viability of CDM cosmologies, we construct N ‐body models of disc galaxies with structural properties derived in analogy to the recent analytical work of Mo, Mao & White. With a series of self-consistent collisionless simulations of galaxy–galaxy mergers we demonstrate that even the discs of very massive dark haloes have no problems developing long tidal tails, provided the halo spin parameter is large enough. For our class of models, the halo-to-disc mass ratio is not a good indicator of the ability to produce tails. Instead, the relative size of disc and halo or, alternatively, the ratio of circular velocity to local escape speed at the half mass radius of the disc is a more useful criterion. This result holds in all CDM models. While tidal tails can provide useful information on the structure of galaxies, it thus appears unlikely that they are able to constrain the values of the cosmological parameters within these models.     

Antarktis: Das CCAMLR-Übereinkommen (Convention on the Conservation of Antarctic Marine Living Resources) und die illegale Überfischung der südlichen Ozeane

Ocean Dynamics - Die Konvention zum Schutz der marinen lebenden Ressourcen der Antarktis (CCAMLR) wurde 1982 ins Leben gerufen. Im Hinblick auf die sich in der Antarktis rapide entwickelnde...     

Very high electrical conductivity beneath the Münchberg Gneiss area in Southern Germany: implications for horizontal transport along shear planes

New magnetotelluric data from the Münchberg Gneiss complex in Southern Germany reveal a zone of extremely high electrical conductivity. 1-D modelling of the data is justified in the period range 0.01 to 10  s. At least three layers are required to explain the steepness of the apparent resistivity curves, and the best-fitting models comprise four layers with successively higher conductivities. The layers of highest conductivity at depths between 2.2 and 3.6  km correlate with pronounced bands of high seismic reflectivity (profile DEKORP 85-4N). The Münchberg complex is today widely recognized as a tectonic klippe, consisting of rocks whose metamorphic and stratigraphic order is inverted rather than overturned. The material was transported into its present position by predominantly horizontal tectonic forces along shear zones. We interpret the high conductivity and high reflectivity as remnants of this transport process.     

Digital elevation models derived from airborne laser scanning point clouds: appropriate spatial resolutions for multi‐temporal characterization and quantification of geomorphological processes

Digital terrain models (DTMs) are a standard data source for a variety of applications. DTM differencing is also widely used for detection and quantification of topographic changes. While several investigations have been made on the accuracy of DTMs, calculated from different kinds of input data, little has been published on the error of DTM differencing, specifically for the quantification of geomorphological processes. In this study, an extensive, multi‐temporal set of airborne laser scanning (ALS) data is used to investigate the accuracy of topographic change calculations in a high alpine environment, caused by different geomorphic processes. Differences from DTMs with cell sizes ranging from 0.25 m to 10 m were calculated and compared to very accurate point‐to‐point calculations for a variety of processes and in nearby stable areas which show no significant surface changes. The representativeness of the DTM differences is then compared to the terrain slope and surface roughness of the investigated areas to show the influence of these parameters on the errors in the differences. Those errors are then taken into account for analyses of the applicability of different cell sizes for the investigation of geomorphic processes with different magnitudes and over different time periods. The analyses show that the error of DTM differences increases with lower point densities and higher roughness and slope values. The higher the error, the greater the differences between two elevation datasets have to be in order to quantify certain morphodynamic processes. Lower point densities and higher roughness and slope values require greater process rates or longer time intervals in order to obtain valid results. Copyright © 2013 John Wiley & Sons, Ltd.     

From new political organizations to changing moral geographies: Unpacking global civil society

The discourse of globalization suggests that territorial and cultural boundaries are increasingly insignificant or even disappearing in today's `world of flows'. More recently, this notion of borderlessness has also suffused broad reaches of the imagination of policy-makers and social scientists in the Western world. Thus, the term `global civil society' was coined to capture the experience and impact of transnational environmental and human rights activism. In this paper, however, it is argued that the concept remains both undertheorized and empirically dubious. In order to analytically `unpack' the concept, I provide a brief summary of an empirical research project on networks of new political organizations in South Asia and the West. The evidence assembled suggests the need to reconceptualize the geographies of transborder solidarity and concern beyond the rhetoric of global civil society.     

Twenty years of soil erosion on-farm measurement: Annual variation,spatial distribution and the impact of conservation programmes for soil loss rates in Switzerland

Long-term field assessments of soil erosion on the landscape scale are very scarce. Such monitoring programmes create sound data regarding severity, extent, frequency and types of soil erosion and the vulnerability of particular crops. In a 20-year monitoring programme between 1997 and 2017, accurate erosion damage mapping was carried out on 203 fields on arable land in the Canton of Berne (Switzerland). During 115 field inspections, 4060 field years and 2165 mapped erosion systems were recorded. Because several soil conservation programmes were implemented during this period, two 10-year time periods (1st October 1997 to 30th September 2007 [P1] and 1st October 2007 to 30th September 2017 [P2]) were established and compared. The soil erosion rate was already low in P1 (mean: 0.74 t ha⁻¹ year⁻¹), but decreased significantly in P2 (mean: 0.20 t ha⁻¹ year⁻¹). During P1 and P2, respectively, 12 and 42% of the fields were without any visible erosion. Within 10 years, erosion occurred on each field on average 3.2 times in P1 and only 1.3 times in P2. Soil losses are spatially concentrated and linked to topographically defined pathways (thalwegs, slope depressions) or human-made flow pathways (wheel tracks, tramlines, headlands). Financial incentives, rising awareness among farmers, innovative contractor farmers and good extension service of cantonal agencies helped conserve 85% of the arable land in the study area with conservation tillage methods by 2015. As a result, soil erosion was significantly reduced. The field-based measurements show that a significant decrease in soil erosion is possible by changes in soil tillage practices and that erosion control is feasible almost everywhere under real-life conditions on farmers’ fields. In this respect, the Frienisberg region is a case example of successful erosion control. © 2020 John Wiley & Sons, Ltd.     

Research and Application of In‐seam Seismic Survey Technology for Disaster‐causing Potential Geology Anomalous Body in Coal Seam

In order to effectively detect potential geology anomalous bodies in coal bearing formation, such as coal seam thickness variation, small faults, goafs and collapse columns, and provide scientific guidance for safe and efficient mining, the SUMMIT-II EX explosion-proof seismic slot wave instrument, produced by German DMT Company, was used to detect the underground channel wave with the help of transmission method, reflection method and transflective method. Region area detection experiment in mining face had been carried out thanks to the advantage of channel wave, such as its great dispersion, abundant geology information, strong anti-interference ability and long-distance detecting. The experimental results showed that: (1) Coal seam thickness variation in extremely unstable coal seam has been quantitatively interpreted with an accuracy of more than 80% generally; (2) The faults, goafs and collapse columns could be detected and predicted accurately; (3) Experimental detection of gas enrichment areas, stress concentration regions and water inrush risk zone has been collated; (4) A research system of disaster-causing geology anomalous body detection by in-seam seismic survey has been built, valuable and innovative achievements have been got. Series of innovation obtained for the first time in this study indicated that it was more effective to detect disaster-causing potential geology anomalies by in-seam seismic survey than by ground seismic survey. It had significant scientific value and application prospect under complex coal seam conditions.