Modelling Transient Ground Surface Temperatures of Past Rockfall Events: Towards a Better Understanding of Failure Mechanisms in Changing Periglacial Environments          下载免费PDF全文

Rachel Luethi  Stephan Gruber  Ludovic Ravanel 《Geografiska Annaler: Series A, Physical Geography》2015,97(4):753-767

Despite the rising interest in mountain permafrost due to climatic changes and a noticed increase of registered rockfall events in the European Alps and other mountain ranges, little is known about transient thermal conditions in the detachment areas of rockfalls. Temperature conditions prior to the rockfall events of 144 past events in the European Alps were modelled with a physically based ground temperature model. To minimise the impact that uncertainty has on interpretations, only relative values were used, that is, percentiles obtained from cumulative distribution functions of the modelled ground surface temperatures from the beginning of the meteorological measurement series up to the event dates. Our results suggest that small and mid‐sized rockfalls (volumes up to 100 000 m³) from high elevation occurred mainly during short‐term periods of unusually high temperatures. This was neither found to be a result of the seasonal distribution (most analysed events in higher elevations occurred from July to September) nor of the longer‐term temporal distribution (most analysed events occurred after 2000) only. Plausible explanations are either a destabilisation related to advective thaw or failure due to stress redistribution caused by large temperature variations. Large deep‐seated rock slope failures (≥100 000 m³) in high elevation occurred all year round.  相似文献   

Deep melting of old subducted oceanic crust recorded by superchondritic Nb/Ta in modern island arc lavas     

Stephan König  Stephan Schuth 《Earth and Planetary Science Letters》2011,301(1-2):265-274

Niobium–tantalum systematics of slab-derived melts are powerful tracers that discriminate residual high-pressure rutile-bearing eclogite from low-pressure garnet-bearing amphibolite in subducting plates. Previously reported low Nb–Ta ratios in modern slab melts suggested a predominance of shallow melting in the presence of residual amphibole and that deep melting of rutile-bearing eclogitic slabs, devoid of residual amphibole, is volumetrically insignificant. This study evaluates Nb/Ta in combination with other trace element systematics of modern intra-oceanic and slab melt-related arc lavas from the south-western volcanic chain of the Solomon Islands that cover over 1000 km of the SW Pacific plate border. After a change of subduction polarity, an old subducted Pacific slab and a recently subducting Indian–Australian slab are both present beneath the arc. Solomon arc lavas show sub- to superchondritic Nb–Ta ratios (ca. 10 to 27) which is the largest range ever reported in modern island arc lavas. The large range of Nb/Ta likely results from enrichment of the depleted sub-arc mantle by two distinct slab-derived melts in addition to fluids. One minor slab melt component is derived from the shallow and recent subducting Indian–Australian plate where amphibole is still a significant residual phase. The second slab melt component is predominant in Solomon arc lavas and can be attributed to deep rutile–eclogite-controlled melting of old subducted Jurassic Pacific oceanic crust where residual amphibole is entirely absent or insignificant. The deep Pacific slab melt component is the most likely origin of the extremely high and superchondritic Nb/Ta signatures that produce the upper half of the observed range of Nb/Ta in Solomon arc lavas. The slab melt component that enriched the sub-arc mantle with an unusually high Nb/Ta signature is derived from an initially intact Pacific plate that was probably subject to a slab break-off event and subsequent melting at depths exceeding 100 km. The geochemical evidence presented here shows that old and cold subducted oceanic crust, which is initially not torn, may resist shallow melting but can melt at greater depths instead. The resulting slab melts are generated in the presence of residual rutile-bearing eclogite and significantly fractionate Nb–Ta ratios which may be of relevance at a global scale.  相似文献   

Characteristics of a Shallow River Plume: Observations from the Saco River Coastal Observing System     

Charles E. Tilburg  Shaun M. Gill  Stephan I. Zeeman  Amy E. Carlson  Timothy W. Arienti  Jessica A. Eickhorst  Philip O. Yund 《Estuaries and Coasts》2011,34(4):785-799

Interest in the coastal dynamics of river plumes has mainly focused on large rivers, but plumes from the more numerous smaller rivers have important local consequences and may, in aggregate, be significant contributors to coastal circulation. We studied the dynamics of the plume from the Saco River in Saco Bay, Gulf of Maine, over a 3-year period. The transport and salinity in the region are governed by river discharge, tides, winds, and interaction with the Western Maine Coastal Current. The dynamics of the flow field vary with location within the plume and discharge. The far-field dynamics of the Saco River plume are dominated by inertial processes (hence qualifying it as a small-scale river plume), during times of low discharge, with low salinity water present both up and downstream of the river mouth, but are dominated by rotational processes during times of high discharge (thus qualifying it as a large-scale river plume), with buoyant water primarily advected downshelf. Near-field dynamics are governed by weak, subcritical flow during low discharge but strongly inertial, supercritical flow during high discharge. Offshore movement of the plume is not governed by Ekman dynamics but is instead a result of discharge, wind-induced vertical mixing, and the geography of the coastline and adjacent islands.  相似文献   

Isolation and purification of Cu-free methanobactin from Methylosinus trichosporium OB3b     

Marie-Laure Pesch  Iso Christl  Kurt Barmettler  Stephan M Kraemer  Ruben Kretzschmar 《Geochemical transactions》2011,12(1):2

Background  

The isolation of highly pure copper-free methanobactin is a prerequisite for the investigation of the biogeochemical functions of this chalkophore molecule produced by methane oxidizing bacteria. Here, we report a purification method for methanobactin from Methylosinus trichosporium OB3b cultures based on reversed-phase HPLC fractionation used in combination with a previously reported resin extraction. HPLC eluent fractions of the resin extracted product were collected and characterized with UV-vis, FT-IR, and C-1s NEXAFS spectroscopy, as well as with elemental analysis and ESI-MS.  相似文献   

Earthquakes in Switzerland and surrounding regions during 2010     

Nicholas Deichmann  John Clinton  Stephan Husen  Benjamin Edwards  Florian Haslinger  Donat Fäh  Domenico Giardini  Philipp Kästli  Urs Kradolfer  Stefan Wiemer 《Swiss Journal of Geoscience》2011,104(3):537-547

This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during 2010. During this period, 407 earthquakes and 85 quarry blasts were detected and located in the region under consideration. With a total of only 19 events with M_L ≥ 2.5, the seismic activity in the year 2010 was below the average over the previous 35 years. The two most noteworthy earthquakes were the M_L 3.4 Barrhorn event near Sankt Niklaus (VS) and the M_L 3.0 event of Feldkirch, both of which produced shaking of intensity IV.  相似文献   

Development and assessment of protective winter covers for marble statuaries of the Schlossbrücke, Berlin (Germany)     

Joerg Ruedrich  York Rieffel  Stephan Pirskawetz  Holger Alpermann  Ute Joksch  Christoph Gengnagel  Frank Weise  Rudolph Plagge  Jianhua Zhao  Siegfried Siegesmund 《Environmental Earth Sciences》2011,63(7-8):1823-1848

The present study documents the results of an inter-disciplinary model project that was planned with the aim of developing an innovative winter covering system for marble statuaries located on the Schlossbrücke (Berlin). Such a system would need to fulfil the various requirements for structural stability, aesthetics, climate and practical use. This applied research represents the first complex scientific study of the sustainability of a winter covering system. The study is characterised by the use of complex scientific instruments such as special laboratory analysis and numerical simulation tools. The interaction between the environment and the artefacts in connection with the innovative winter covering structures were studied by extensive climatic monitoring.  相似文献   

Characterization on arsenic sorption and mobility of the sediments of Chia-Nan Plain, where Blackfoot disease occurred   总被引：1，自引：1，他引：0  

Zhaohui Li  Hanlie Hong  Jiin-Shuh Jean  Andria J. Koski  Chia-Chuan Liu  Selim Reza  Jeffrey J. Randolph  Stephan R. Kurdas  Jonathan H. Friend  Sarah J. Antinucci 《Environmental Earth Sciences》2011,64(3):823-831

Higher levels of arsenic in the aquifers of Chia-Nan Plain in southwestern Taiwan were attributed to the cause of Blackfoot disease in the area half a century ago. Although extensive studies were conducted on the occurrence, speciation, mobility, and transport of arsenic in the region, the relationship between arsenic adsorption by different aquifer materials and the concentration and speciation of arsenic in these aquifers was poorly delineated. This study focused on characterization of sediments in the region, as well as determination of relations between arsenic adsorption and other geochemical and clay mineralogical properties of the sediments. The arsenic adsorption capacity was positively related to the clay minerals, Fe, and Mn contents in the sediments. The higher arsenic adsorption capacity of the sediments served as a sink for the arsenic during its transport from the central mountains to the coast and as a source for its release under reduced environment and in the presence of humic substances.  相似文献   

Earthquakes in Switzerland and surrounding regions during 2012     

Tobias Diehl  Nicholas Deichmann  John Clinton  Stephan Husen  Toni Kraft  Katrin Plenkers  Benjamin Edwards  Carlo Cauzzi  Clotaire Michel  Philipp Kästli  Stefan Wiemer  Florian Haslinger  Donat Fäh  Urs Kradolfer  Jochen Woessner 《Swiss Journal of Geoscience》2013,106(3):543-558

This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during 2012. During this period, 497 earthquakes and 88 quarry blasts were detected and located in the region under consideration. With a total of only 13 events with M_L ≥ 2.5, the seismic activity in the year 2012 was far below the average over the previous 37 years. Most noteworthy were the earthquake sequence of Filisur (GR) in January with two events of M_L 3.3 and 3.5, the M_L 4.2 and M_L 3.5 earthquakes at a depth of 32 km below Zug in February and the M_L 3.6 event near Vallorcine in October. The epicentral intensity of the M_L 4.2 event close to Zug was IV, with a maximum intensity of V reached in a few areas, probably due to site amplification effects.  相似文献   

Traffic-related immissions and their impact on historic buildings: implications from a pilot study at two German cities   总被引：1，自引：1，他引：0  

Michael Auras  Silvia Beer  Petra Bundschuh  Joachim Eichhorn  Martin Mach  Dirk Scheuvens  Michael Schorling  Jonas von Schumann  Rolf Snethlage  Stephan Weinbruch 《Environmental Earth Sciences》2013,69(4):1135-1147

Besides the enormous improvement of air quality in Germany due to the reduction of sulphur dioxide emissions in the last decades, high immissions of nitrogen oxides and fine particulate matter are frequently observed at traffic-rich urban sites. The changed chemical composition of air pollution requires a new investigation of its impact on historic buildings constructed of natural stone. In a pilot study a multi-disciplinary approach was chosen to obtain information on the actual pollution situation of historic buildings and monuments at traffic hotspots in Germany. The study concentrated on the two German cities of Munich and Mainz of different size, traffic volume and stone inventory. Dose–response functions were calculated to demonstrate the change of impact of different pollutants over the last three decades, and for comparison of traffic hotspots and housing areas of both cities. Numeric modelling on a city-scale was used to identify the historic buildings and monuments affected by elevated traffic immissions. Because a relevant part of these pollutants is dominated by short-range transport, the differences of wind speed and deposition rates were calculated using a street-scale 3D flow and dispersion model regarding traffic volume, wind regime and adjacent buildings. Finally, particulate matter was sampled at different positions of two buildings heavily exposed to traffic emissions. Individual particles were investigated by environmental scanning electron microscopy. After classification of the particles into different chemical groups, the fraction of traffic-induced particulate matter was quantified. Summarizing the results, it must be stated that soiling by traffic-related particulate matter, deposition of nitrates deriving from exhaust emission and other diffusely emitted components bear a severe damage potential for natural building stone at least locally at traffic-rich urban sites.  相似文献   

Discovering relative motion patterns in groups of moving point objects     

Patrick Laube Corresponding author  Stephan Imfeld  Robert Weibel 《International journal of geographical information science》2013,27(6):639-668

Technological advances in position‐aware devices are leading to a wealth of data documenting motion. The integration of spatio‐temporal data‐mining techniques in GIScience is an important research field to overcome the limitations of static Geographic Information Systems with respect to the emerging volumes of data describing dynamics. This paper presents a generic geographic knowledge discovery approach for exploring the motion of moving point objects, the prime modelling construct to represent GPS tracked animals, people, or vehicles. The approach is based on the concept of geospatial lifelines and presents a formalism for describing different types of lifeline patterns that are generalizable for many application domains. Such lifeline patterns allow the identification and quantification of remarkable individual motion behaviour, events of distinct group motion behaviour, so as to relate the motion of individuals to groups. An application prototype featuring novel data‐mining algorithms has been implemented and tested with two case studies: tracked soccer players and data points representing political entities moving in an abstract ideological space. In both case studies, a set of non‐trivial and meaningful motion patterns could be identified, for instance highlighting the characteristic ‘offside trap’ behaviour in the first case and identifying trendsetting districts anticipating a political transformation in the latter case.  相似文献