Interferometric/daylight seismic imaging   总被引：8，自引：0，他引：8  

G. T. Schuster  J. Yu  J. Sheng  J. Rickett 《Geophysical Journal International》2004,157(2):838-852

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IGU Reports: International Geographical Union/Union Géographique Internationale     

Patrick Armstrong  Ute Wardenga 《GeoJournal》1998,44(2):175-175

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The role of gravitational supernovae in the Galactic evolution of the Li, Be and B isotopes     

Carlos Abia  Jordi Isern  & Ute Lisenfeld 《Monthly notices of the Royal Astronomical Society》1998,299(4):1007-1012

The observed Be and B relationships with metallicity clearly support the idea that both elements have a primary origin and that they are produced by the same class of objects. Spallation by particles accelerated during gravitational supernova events (SNII, SNIb/c) seems to be a likely origin. We show, in the context of a model of chemical evolution, that it is possible to solve the Li, Be and B abundance puzzle with the yields recently proposed by Ramaty et al., provided that SNII are unable to accelerate helium nuclei significantly and that different mechanisms are allowed to act simultaneously.  相似文献   

The refraction seismic experiment GRANU95 in the Saxothuringian belt, southeastern Germany   总被引：1，自引：0，他引：1  

Enderle  Schuster  Prodehl  Schulze  & Bribach 《Geophysical Journal International》1998,133(2):245-259

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Inverse theory in the earth sciences—an introductory overview with emphasis on Gandin's method of optimum interpolation     

Ute Christina Herzfeld 《Mathematical Geosciences》1996,28(2):137-160

In 1963, Gandin published a monograph on “optimum interpolation for the objective analysis of meteorological fields, ? a method that is similar mathematically to geodetical least-squares prediction and collocation, simple kriging, and spectral interpolation. The common problem is the interpolation or extrapolation or estimation of a continuous spatial property from finitely many observations. Gandin 's method is presented in an inverse-theoretical context with focus on a methodological comparison with related methods. Underlying mathematical assumptions as well as geological implications are discussed. An introductory overview of inverse methods in the earth sciences is given, with emphasis on methods with a structure analysis step.  相似文献   

Causes of low-frequency ground motion amplification in the Salt Lake Basin: the case of the vertically incident P wave     

Kim B. Olsen  Gerard T. Schuster 《Geophysical Journal International》1995,122(3):1045-1061

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Is the ocean floor a fractal?     

Ute C. Herzfeld  Isaac I. Kim  John A. Orcutt 《Mathematical Geosciences》1995,27(3):421-462

The topographic structure of the ocean bottom is investigated at different scales of resolution to answer the question: Can the seafloor be described as a fractal process? Methods from geostatistics, the theory of regionalized variables, are used to analyze the spatial structure of the ocean floor at different scales of resolution. The key to the analysis is the variogram criterion: Self-similarity of a stochastic process implies self-similarity of its variogram. The criterion is derived and proved here: it also is valid for special cases of self-affinity (in a sense adequate for topography). It has been proposed that seafloor topography can be simulated as a fractal (an object of Hausdorff dimension strictly larger than its topological dimension), having scaling properties (self-similarity or self-affinity). The objective of this study is to compare the implications of these concepts with observations of the seafloor. The analyses are based on SEABEAM bathymetric data from the East Pacific Rise at 13°N/104°W and at 9°N/104°W and use tracks that run both across the ridge crest and along the ridge flank. In the geostatistical evaluation, the data are considered as a stochastic process. The spatial continuity of this process is described by variograms that are calculated for different scales and directions. Applications of the variogram criterion to scale-dependent variogram models yields the following results: Although the seafloor may be a fractal in the sense of the definition involving the Hausdorff dimension, it is not self-similar, nor self-affine (in the given sense). Mathematical models of scale-dependent spatial structures are presented, and their relationship to geologic processes such as ridge evolution, crust formation, and sedimentation is discussed.  相似文献   

Coastal conglomerates around the Hadjer el Khamis inselbergs (western Chad,central Africa): new evidence for Lake Mega‐Chad episodes     

Mathieu Schuster  Philippe Duringer  Jean‐Francois Ghienne  Patrick Vignaud  Alain Beauvilain  Hassan Taisso Mackaye  Michel Brunet 《地球表面变化过程与地形》2003,28(10):1059-1069

This paper reports on a study dealing with the rhyolitic inselbergs of Hadjer el Khamis that formed palaeoislands during Lake Mega‐Chad events. Field observations have shown that: (1) conglomeratic patches of immature to mature clasts are preserved at the feet of the Hadjer el Khamis inselbergs; (2) in cross‐section, their pro?le reveals a well de?ned cliff–platform junction at a constant elevation (325 m). The monolithological clasts show all degrees of roundness, from angular cobbles to well rounded pebbles. This wide range of maturity suggests a coastal origin for these cobbles. The system was permanently fed with angular clasts, which were progressively worn by waves. Cobbles that were wave‐worked for the longest time are the best rounded. The cliff–platform junction is the result of erosion by waves, which attacked and undercut the inselberg cliffs during Lake Mega‐Chad events. Asymmetrical erosion pro?les moreover suggest a wind regime dominated by SW to NE oriented winds. These interpretations have two implications. The elevation of the cliff–platform junction is an indication of the highest water level of Lake Mega‐Chad at 320–325 m, which is in agreement with other observations elsewhere in the basin. The SW to NE oriented winds show that monsoon‐related winds were prevalent during Lake Mega‐Chad events, suggesting the Inter‐Tropical Convergence Zone was located higher in latitude than today. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

A magnetotelluric study of the Damara Belt in Namibia: 1. Regional scale conductivity anomalies     

Oliver Ritter  Ute WeckmannTim Vietor  Volker Haak 《Physics of the Earth and Planetary Interiors》2003,138(2):71-90

The Namibian margin is dominated by the late Proterozoic to early Cambrian fold belts of the Damara Orogen, which wrap around and separate the Congo and Kalahari Cratons. This mosaic of relatively ‘soft’ fold belts and ‘hard’ cratons apparently controlled the path for the opening of the South Atlantic in the early Cretaceous. The continents split along the coast-parallel fold belts of the Damara Orogen while the inland fold belt (Damara Belt) was effected by extension and widespread igneous intrusion but never developed to the rift stage. This paper is concerned with the interpretation of magnetotelluric (MT) data along a 200 km NW-SE profile across the Damara Belt in NW Namibia. The regional, two-dimensional electrical resistivity model and the induction vector data exhibit three distinctive zones: (i) a generally very resistive upper crust which is typical for the granites and metasediments of the Damara Belt, (ii) two subvertical conductors in upper to mid-crustal levels which correlate with major tectonic zone boundaries and (iii) a highly conductive middle to lower crust in the southern part of the profile. The geometry of the conductive structures could reflect a regional shear system in which upper crustal listric faults pass into a detachment zone in the middle crust. We interpret the high electrical conductivity in terms of graphite (or other forms of mineralization) enrichment along the shear planes. This zone of crustal weakness may have originated in Pre-Damara times and had probably experienced several episodes of crustal reactivation before the intrusion of basaltic dike swarms during the Cretaceous rifting and magmatism associated with the opening of the South Atlantic.  相似文献   

Images of the magnetotelluric apparent resistivity tensor     

Ute Weckmann  Oliver Ritter  Volker Haak 《Geophysical Journal International》2003,155(2):456-468

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