Characterizing swells in the southern Pacific from seismic and infrasonic noise analyses     

Guilhem Barruol  Dominique Reymond  Fabrice R. Fontaine  Olivier Hyvernaud  Vincent Maurer  Keitapu Maamaatuaiahutapu 《Geophysical Journal International》2006,164(3):516-542

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Internal structure of an alpine rock glacier based on crosshole georadar traveltimes and amplitudes     

Martin Musil  Hansruedi Maurer  Klaus Hollinger  Alan G. Green 《Geophysical Prospecting》2006,54(3):273-285

Rapid melting of permafrost in many alpine areas has increased the probability of catastrophic rock slides. In an attempt to provide critical structural information needed for the design and implementation of suitable mitigation procedures, we have acquired low frequency (22 MHz) cross‐hole radar data from within a fast‐moving rock glacier, an important form of alpine permafrost. Since the ice, rock and pockets of water and air found in the underground of high alpine areas have very different dielectric permittivities and electrical conductivities, the radar method was well‐suited for investigating the structure and state of the rock glacier. Our interpretation of the radar velocities and attenuations was constrained by geomorphological observations, borehole lithological logs and the results of a surface seismic survey. The radar data revealed the existence of a discontinuous 7–11 m thick ice‐rich zone distinguished by high velocities (0.14–0.17 m/ns) and low attenuations (0.04–0.09 m^?1) and a thin underlying ice‐free zone characterized by moderate velocities (0.11–0.12 m/ns) and low attenuations (0.04–0.09 m^?1). Beneath these two zones, we observed a prominent band of high velocities (0.14–0.17 m/ns) and moderately high attenuations (0.10–0.20 m^?1) associated with unconsolidated glacial sediments and numerous large air‐filled voids, which in the past were probably filled with ice. At greater depths, the variably dry to water‐saturated sediments were represented by generally lower velocities (0.08–0.10 m/ns) and higher attenuations (0.16–0.24 m^?1). The bedrock surface was represented by an abrupt ～0.03 m/ns velocity increase. We speculate that the disappearance of ice, both laterally and with depth, occurred during the past one to two decades.  相似文献   

Sedimentological and palynological constraints on the basal Triassic sequence in Central Switzerland     

Christian Gisler  Peter A. Hochuli  Karl Ramseyer  Hansruedi Bläsi  Fritz Schlunegger 《Swiss Journal of Geoscience》2007,100(2):263-272

In Central Switzerland, Mesozoic sedimentation began after erosion and peneplainisation of the Hercynian relief and late Paleozoic continental deposition in SW-NE striking pull-apart basins. The first Triassic sedimentary sequence overlaying a weathered crystalline basement consists of a relatively thin (<10 m), lithologically highly variable unit with coarse-grained siliciclastic deposits at the base, grading into a mixed sandstone/shale-dolomite sequence followed by well-bedded dolomites with chert nodules.Sedimentary texture analyses and petrological investigations revealed four different sedimentary units starting at the base with a regolith unit that represents the weathered crystalline basement. It is overlain by terrestrial plain deposits, followed by mixed siliciclastic-carbonaceous sediments and a sequence of dolomites, deposited between the supralittoral and eulittoral zones of a tidal flat (Mels-Formation), and the eulittoral to sublittoral zones of a carbonate tidal flat environment (Röti-Dolomit), respectively.Palynological data from four localities in Central Switzerland indicate a heterochronous early Anisian age (Aegean – Bithynian/Pelsonian) for the supra- to eulittoral mixed siliciclastic-carbonaceous sediments. These new biostratigraphic ages suggest that the first Triassic marine transgression in Central Switzerland is time equivalent with those of the basal Wellendolomit in Northern Switzerland but slightly older than in the Germanic Basin. Consequently, Central Switzerland was located at this time at the northern shoreline of the Tethys and not on the southern limit of the Germanic Basin.  相似文献   

Uncertainty in hydrologic impacts of climate change in the Sierra Nevada, California, under two emissions scenarios   总被引：7，自引：4，他引：7  

Edwin P. Maurer 《Climatic change》2007,82(3-4):309-325

A hydrologic model was driven by the climate projected by 11 GCMs under two emissions scenarios (the higher emission SRES A2 and the lower emission SRES B1) to investigate whether the projected hydrologic changes by 2071–2100 have a high statistical confidence, and to determine the confidence level that the A2 and B1 emissions scenarios produce differing impacts. There are highly significant average temperature increases by 2071–2100 of 3.7°C under A2 and 2.4°C under B1; July increases are 5°C for A2 and 3°C for B1. Two high confidence hydrologic impacts are increasing winter streamflow and decreasing late spring and summer flow. Less snow at the end of winter is a confident projection, as is earlier arrival of the annual flow volume, which has important implications on California water management. The two emissions pathways show some differing impacts with high confidence: the degree of warming expected, the amount of decline in summer low flows, the shift to earlier streamflow timing, and the decline in end-of-winter snow pack, with more extreme impacts under higher emissions in all cases. This indicates that future emissions scenarios play a significant role in the degree of impacts to water resources in California.  相似文献   

Ground-based observations of an isolated substorm     

B. Theile  H. Maurer  E. Nielsen  R.A. Greenwald  A. Ranta 《Planetary and Space Science》1980,28(7):763-779

An isolated substorm occurred in Northern Scandinavia on 1 March, 1977 around magnetic midnight. The ionospheric phenomena associated with this substorm were studied by ground magnetometers, the Scandinavian Twin Auroral Radar Experiment (STARE), riometers and an all-sky camera. The physical properties of the auroral electrojet are determined from the ground magnetic field and the ionospheric electric field data. Mid and low latitude magnetic field data show evidence of field-aligned current flow. It is shown that the enhancement of the electrojet's current density is essentially determined by an increase in the ionospheric conductivity. The current system derived from the data of this study corresponds to a model of Yasuhara et al. (1975a).  相似文献   

Evaluation of sludge dumping off Delaware Bay     

L Watling  W Leathem  P Kinner  C Wethe  D Maurer 《Marine pollution bulletin》1974,5(3):39-42

Sewage sludge from Philadelphia and Camden has been dumped off the mouth of Delaware Bay since 1961. Local residents have claimed that sludge is washed ashore, is a health hazard and has impoverished the fauna of the seabed in the area. In the survey reported here, an assessment has been made of the composition and abundance of the benthic marine fauna of the dumping grounds. The results suggest that dominant species of the area are changing as particulate organic matter accumulates.  相似文献   

Triassic stratigraphy,facies and evolution of the Arabian shelf in the northern United Arab Emirates     

Florian Maurer  Roberto Rettori  Rossana Martini 《International Journal of Earth Sciences》2008,97(4):765-784

This study provides a reconstruction of the Late Permian and Triassic depositional history of the Arabian shelf in the northern United Arab Emirates based on facies analysis and foraminiferal biostratigraphy. The presented data show that sedimentation occurred in three major sequences. From the Late Permian to Olenekian carbonates and evaporites were deposited in restricted lagoons and tidal flats. After a hiatus, sedimentation resumed and continued until the Late Ladinian/Carnian, leading to the deposition of a carbonate platform dominated by peritidal dolostones. A period of shelf exposure and erosion, spanning from the Carnian to Norian, was followed by the third major sequence with sedimentation into the Early Jurassic. During this third depositional sequence sedimentation changed from pure carbonate into mixed carbonate–siliciclastic deposits. This transition reflects the global regression of the sea in the Late Triassic (Triasina hantkeni Zone) and the increased erosion of large parts of the Arabian hinterland. A comparison of the evolution of the Arabian shelf in the study area with chronostratigraphic reference schemes for the Arabian Plate reveals remarkable differences in the distribution of Middle and Upper Triassic sequences. These are most likely the result of poor biostratigraphic control on previously studied formations in the region.  相似文献   

Discrete tomography and joint inversion for loosely connected or unconnected physical properties: application to crosshole seismic and georadar data sets   总被引：2，自引：0，他引：2  

M. Musil  H. R. Maurer  A. G. Green 《Geophysical Journal International》2003,153(2):389-402

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Initial hydro‐geomorphic development and rill network evolution in an artificial catchment     

Horst H. Gerke  Thomas Maurer  Rossen Nenov 《地球表面变化过程与地形》2013,38(13):1496-1512

The formation of erosion rills and gullies is a critical step in land surface development, but possibilities to study initial unaffected surface development under natural conditions and with well‐defined initial and boundary conditions are rare. The objective of this study was to characterize rill network development from ’point zero’ in the artificially‐created catchment ‘Hühnerwasser’. To ensure unaffected development, the study was largely restricted to the analysis of remotely‐sensed data. We analyzed a series of photogrammetry‐based digital elevation models (DEMs) for 10 points in time, over a period of five years and beginning with the initial state. The evolving erosion rill network was quantitatively described based on mapping from aerial photographs. DEMs and rill network maps were combined to specifically analyze the development of morphometry for different parts of the network and to characterize energy dissipation and connectivity. The restriction to remote‐sensing data did not allow for analyzing specific processes governing rill network development, nevertheless, two major development phases could be characterized. We observed a phase of growth of the rill network along with variations in drainage patterns during the first two years of development and a subsequent phase of reduction of its area along with comparably stable patterns. Region‐specific analysis of morphometry indicates that, besides effects of changing sediment characteristics and vegetation cover development, locally evolving hydro‐geomorphic feedback cycles influenced this development. Results show an increasing similarity of overall statistical characteristics (e.g. drainage density) for two parts of the catchment, but a persistent influence of initial conditions on specific rill geometry. The observed development towards higher orderliness and increased connectivity is consistent with experiments and concepts on drainage network evolution across scales; however, we did not observe major influences of rill piracy and cross grading or a reduction of energy dissipation with network development. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

The middle to late Triassic Bänkerjoch and Klettgau formations of northern Switzerland     

Peter Jordan  Johannes S. Pietsch  Hansruedi Bläsi  Heinz Furrer  Nicole Kündig  Nathan Looser  Andreas Wetzel  Gaudenz Deplazes 《Swiss Journal of Geoscience》2016,109(2):257-284

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