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91.
92.
Survey and monitoring of landslide displacements by means of L-band satellite SAR interferometry 总被引:2,自引:2,他引:2
Tazio Strozzi Paolo Farina Alessandro Corsini Christian Ambrosi Manfred Thüring Johannes Zilger Andreas Wiesmann Urs Wegmüller Charles Werner 《Landslides》2005,2(3):193-201
This paper illustrates the capabilities of L-band satellite SAR interferometry for the investigation of landslide displacements.
SAR data acquired by the L-band JERS satellite over the Italian and Swiss Alps have been analyzed together with C-band ERS-1/2
SAR data and in situ information. The use of L-band SAR data with a wavelength larger than the usual C-band, generally considered
for ground motion measurements, reduces some of the limitations of differential SAR interferometry, in particular, signal
decorrelation induced by vegetation cover and rapid displacements. The sites of the Alta Val Badia region in South Tyrol (Italy),
Ruinon in Lombardia (Italy), Saas Grund in Valais (Switzerland) and Campo Vallemaggia in Ticino (Switzerland), representing
a comprehensive set of different mass wasting phenomena in various environments, are considered. The landslides in the Alta
Val Badia region are good examples for presenting the improved performance of L-band in comparison to C-band for vegetated
areas, in particular concerning open forest. The landslides of Ruinon, Saas Grund, and Campo Vallemaggia demonstrate the strength
of L-band in observing moderately fast displacements in comparison to C-band. This work, performed with historical SAR data
from a satellite which operated until 1998, demonstrates the capabilities of future planned L-band SAR missions, like ALOS
and TerraSAR-L, for landslide studies. 相似文献
93.
Urs Schrer Jacques Kornprobst Marie-Odile Beslier Gilbert Boillot Jacques Girardeau 《Earth and Planetary Science Letters》1995,130(1-4)
The thinned continental crust of the west Galicia margin is bound by a belt of serpentinized peridotites (‘peridotite ridge’) lying about 300 km off the coast in the North Atlantic ocean. From this ridge, a gabbro and a chlorite rock were studied in an attempt to substantiate rift-related subcontinental magmatism, occurring prior to sea-floor spreading. U-Pb dating of 13 different zircon fractions yields a precise age of 122.1 ± 0.3 Ma (2σ) for the emplacement of the chlorite rock protolith, from which more than 50% of Si and alkali-calc-alkali elements were lost during greenschist facies tectonometamorphism. Sr and Nd isotope signatures suggest that the gabbro and chlorite rock protoliths were derived from mantle sources that were moderately depleted in LILE, relative to a chondritic reservoir. No evidence for the presence of continental material in the magma source regions can be observed. From the new zircon age of 122.1 ± 0.3 Ma, and earlier determined39Ar40Ar age of 122.0 ± 0.6 Ma for amphibole from the same locality, it can be documented that magma formation, solidification and unroofing of the mantle rocks occurred during a short period of time of about 3.4 Ma, which means that the peridotite ridge detached from the continent and rose to the surface immediately after, or even coevally with mantle melting. 相似文献
94.
The distribution of the elements F, Cl, Br and I was analysed in layers removed stepwise from Antarctic H5 and H6 chondrites. All meteorites show higher concentrations of these elements on their surfaces than in their interiors. The degree of halogen enrichment cannot be correlated with the degree of visual weathering and is proportional to the time the meteorites were residing on the surface of the Antarctic ice. During this period, aerosols, salts and gaseous components are deposited on the surfaces of the meteorites and diffuse into their interior. The observed contamination level of the meteorites is influenced by leaching properties and diffusion behaviour of the individual halogens. The major contamination source for F, Cl and probably Br is air-borne seaspray; for I it is the gaseous compound methyl iodide (CH3I) produced by biological processes in the sea. Methyl iodide and its oxidation products formed in the Antarctic atmosphere (e.g., I2) can be transported over longer distances to the interior of Antarctica than air-borne seaspray. Therefore, the ratio of the halogen contamination is related to the collection site of the meteorites. All meteorites that were found in the Antarctic interior are contaminated to a lesser degree by F, Cl and Br relative to I than those found near the coast. The measured enrichment ratio of I/F is a function of the distance between the collection site and the open sea, and increases from the Allan Hills to the Thiel Mountains. By revealing the degree of contamination of a meteorite it is possible to determine its maximum surface residence time on the Antarctic ice. 相似文献
95.
The age and origin of five leucogranites from the High and Tethys Himalaya, and two country-rock gneisses were investigated by UPb dating of zircon fractions and single grains, and fractions of monazite. Additionally, ThU concentrations in whole rock powders and isotopic compositions of Pb in leached K-feldspars were determined. Monazites yield ages of 16.8 ± 0.6 m.y. for the Nialam migmatite-granite, 15.1 ± 0.5 m.y. for the Lhagoi Kangri granite, 14.3 ± 0.6 m.y. for a granite from Mt. Everest, and 9.8 ± 0.7 m.y. and 9.2 ± 0.9 m.y. for two varieties of the Maja granite. These data, together with monazite ages of 21.9 ± 0.2 and 24.0 ± 0.4 m.y., determined earlier on the Makalu granite [1], substantiate a period of intracontinental granite emplacements from 24 to 9 m.y. ago, i.e. from uppermost Oligocene to late Miocene times. Such a period of plutonic activity is consistent with the view that all these granites result from intracrustal melting following the collision of India with Eurasia. Furthermore, the individual ages, together with structural relationships between granites and country rocks suggest that granite formation and tectono-metamorphism occurred as alternating and strongly related processes with a periodicity of 7 to 9 m.y. Inherited lead components, present in all granite zircons point to large proportions of Precambrian material in the magma source regions, up to 2200 m.y. old.ThU systematics between monazite and country rocks indicate that U has been leached from most of the granites after crystallisation of monazite.Zircon dating of the Kangmar granite gneiss, which occurs in a window through the Tethys Himalayan sediments, shows that this pluton, transformed to a gneiss during the Alpine orogeny, crystallised in lowermost Palaeozoic times 562 ± 4 m.y. ago. 相似文献
96.
Urs Neu 《Boundary-Layer Meteorology》1995,73(1-2):189-193
The reduction of ozone in the nocturnal residual layer by vertical mixing to the surface was investigated for several summer smog episodes on the Swiss plateau in the years 1990 and 1991. Using a limited data set of SODAR measurements and surface ozone concentrations, a parameterization of the ozone depletion in the nocturnal residual layer due to vertical mixing to the ground is proposed. This model is not intended to be physically complete but is rather simple with limited input information required. The nocturnal ozone reduction within the whole planetary boundary layer (nocturnal boundary layer plus residual layer) over the complex terrain of the Swiss plateau for the days investigated is between 20 and 50%. 相似文献
97.
Chemical and geochemical studies of Lake Biel 总被引:1,自引:0,他引:1
Urs P. Nyffeler Paul W. Schindler Urban E. Wirz Dieter M. Imboden 《Aquatic Sciences - Research Across Boundaries》1983,45(1):45-61
The mixing and transport processes in Lake Biel have been studied using the heat and excess Rn-222 as natural tracers. The
mixing parameters were established in terms of coefficients of eddy diffusion in a two-dimensional box model. To account for
observed transient Rn-222 distribution, transport by advection had to be included in the model calculations.
Part I: Peter W. Santschi and Paul W. Schindler: A mass balance for Lake Biel and its implications for the rates of erosion
of the drainage area. Schweiz. Z. Hydrol.39, 182–200 (1977). 相似文献
98.
To elucidate the age and origin of seamounts in the eastern North Atlantic, 54 titanite and 10 zircon fractions were dated by the U-Pb chronometer, and initial Pb, Sr, and Hf isotope ratios were measured in feldspars and zircon, respectively. Rocks analyzed are essentially trachy-andesites and trachytes dredged during the “Tore Madeira” cruise of the Atalante in 2001. The ages reveal different pulses of alkaline magmatism occurring at 104.4 ± 1.4 (2σ) Ma and 102.8 ± 0.7 Ma on the Sponge Bob seamount, at 96.3 ± 1.0 Ma on Ashton seamount, at 92.3 ± 3.8 Ma on the Gago Coutinho seamount, at 89.3 ± 2.3 Ma and 86.5 ± 3.4 Ma on the Jo Sister volcanic complex, and at 88.3 ± 3.3 Ma, 88.2 ± 3.9, and 80.5 ± 0.9 Ma on the Tore locality. No space-time correlation is observed for alkaline volcanism in the northern section of the Tore-Madeira Rise, which occurred 20-30 m.y. after opening of the eastern North Atlantic. Initial isotope signatures are: 19.139-19.620 for 206Pb/204Pb, 15.544-15.828 for 207Pb/204Pb, 38.750-39.936 for 208Pb/204Pb, 0.70231-0.70340 for 87Sr/86Sr, and +6.9 to +12.9 for initial epsilon Hf. These signatures are different from Atlantic MORB, the Madeira Archipelago and the Azores, but they lie in the field of worldwide OIB. The Cretaceous seamounts therefore seem to be generated by melts from a OIB-type source that interact with continental lithospheric mantle lying formerly beneath Iberia and presently within the ocean-continent transition zone. Inheritance in zircon and high 207Pb of initial Pb substantiate the presence of very minor amounts of continental material in the lithospheric mantle. A long-lived thermal anomaly is the most plausible explanation for alkaline magmatism since 104 Ma and it could well be that the same anomaly is still the driving force for tertiary and quaternary alkaline magmatism in the eastern North Atlantic region. This hypothesis is agreement with the plate-tectonic position of the region since Cretaceous time, including an about 30° anti-clockwise rotation of Iberia. 相似文献
99.
Felix J. Herrmann Urs Böniger Dirk Jacob Verschuur 《Geophysical Journal International》2007,170(2):781-799
100.
Patrick Henkel Dimitrios Psychas Christoph Günther Urs Hugentobler 《Journal of Geodesy》2018,92(10):1199-1217
Precise point positioning with integer ambiguity resolution requires precise knowledge of satellite position, clock and phase bias corrections. In this paper, a method for the estimation of these parameters with a global network of reference stations is presented. The method processes uncombined and undifferenced measurements of an arbitrary number of frequencies such that the obtained satellite position, clock and bias corrections can be used for any type of differenced and/or combined measurements. We perform a clustering of reference stations. The clustering enables a common satellite visibility within each cluster and an efficient fixing of the double difference ambiguities within each cluster. Additionally, the double difference ambiguities between the reference stations of different clusters are fixed. We use an integer decorrelation for ambiguity fixing in dense global networks. The performance of the proposed method is analysed with both simulated Galileo measurements on E1 and E5a and real GPS measurements of the IGS network. We defined 16 clusters and obtained satellite position, clock and phase bias corrections with a precision of better than 2 cm. 相似文献