Dynamical friction force exerted on spherical bodies     

O. Esquivel †  B. Fuchs 《Monthly notices of the Royal Astronomical Society》2007,378(3):1191-1195

We present a rigorous calculation of the dynamical friction force exerted on a spherical massive perturber moving through an infinite homogenous system of field stars. By calculating the shape and mass of the polarization cloud induced by the perturber in the background system, which decelerates the motion of the perturber, we recover Chandrasekhar's drag force law with a modified Coulomb logarithm. As concrete examples, we calculate the drag force exerted on a Plummer sphere or a sphere with the density distribution of a Hernquist profile. It is shown that the shape of the perturber only affects the exact form of the Coulomb logarithm. The latter converges on small scales because encounters of the test and field stars with impact parameters less than the size of the massive perturber become inefficient. We confirm in this way the earlier results based on the impulse approximation of small angle scatterings.  相似文献   

Wide-angle vibroseis test across the Rhine graben   总被引：1，自引：0，他引：1  

B. Damotte  K. Fuchs  E. Lüschen  F. Wenzel  R. Schlich  G. Toreilles 《Geophysical Journal International》1987,89(1):313-318

Summary. As a joint operation of ECORS and DEKORP, a deep wide-angle seismic experiment using vibrators was carried out in the autumn of 1984. The object was to get information on the deep crust under the Rhine graben without crossing through sedimentary layers. Offsets were in the range of 50 to 89 km. In the first phase, two vibration points were executed in the Vosges mountains. A signal was received in the Black Forest from solely the farthest VP. In the second phase, fourteen VPs were executed in the Black Forest. No stacking or correlation was performed in the field in France. The quality of the results is good only if an equalization is applied before vertical stacking and correlation in the computing centre.  相似文献   

Stress evaluation in offshore regions of Norway     

Holger Spann  Martin Brudy  Karl Fuchs 《地学学报》1991,3(2):148-152

A review has been undertaken of all available information on crustal stresses in Norwegian continental shelf and North Sea. The data have principally come from the results of borehole breakouts, supplemented by focal mechanisms. A simple model of a soft linear inclusion was developed to explain the rapid changes in stress orientation in the Central Graben area. This example indicates that the stress field is affected locally by the geological or structural environment.  相似文献   

Scalar field haloes as gravitational lenses     

Franz E. Schunck  Burkhard Fuchs  Eckehard W. Mielke 《Monthly notices of the Royal Astronomical Society》2006,369(1):485-491

A non-topological soliton model with a repulsive scalar self-interaction of the Emden type provides a constant-density core, similarly as the empirical Burkert profile of dark matter (DM) haloes. As a further test, we derive the gravitational lens properties of our model, in particular, the demarcation curves between 'weak' and 'strong' lensing. Accordingly, strong lensing with typically three images is almost three times more probable for our solitonic model than for the Burkert fit. Moreover, some prospective consequences of a possible flattening of DM haloes are indicated.  相似文献   

Scales of Heterogeneities in the Continental Crust and Upper Mantle   总被引：2，自引：0，他引：2  

M. Tittgemeyer  F. Wenzel  T. Ryberg  K. Fuchs 《Pure and Applied Geophysics》1999,156(1-2):29-52

—A seismological characterization of crust and upper mantle can refer to large-scale averages of seismic velocities or to fluctuations of elastic parameters. Large is understood here relative to the wavelength used to probe the earth.¶In this paper we try to characterize crust and upper mantle by the fluctuations in media properties rather than by their average velocities. As such it becomes evident that different scales of heterogeneities prevail in different layers of crust and mantle. Although we cannot provide final models and an explanation of why these different scales exist, we believe that scales of inhomogeneities carry significant information regarding the tectonic processes that have affected the lower crust, the lithospheric and the sublithospheric upper mantle.¶We focus on four different types of small-scale inhomogeneities (1) the characteristics of the lower crust, (2) velocity fluctuations in the uppermost mantle, (3) scattering in the lowermost lithosphere and on (4) heterogeneities in the mantle transition zone.  相似文献   

Statistical landslide susceptibility assessment of the Mansehra and Torghar districts,Khyber Pakhtunkhwa Province,Pakistan     

Jewgenij Torizin  Michael Fuchs  Adnan Alam Awan  Ijaz Ahmad  Sardar Saeed Akhtar  Simon Sadiq  Asif Razzak  Daniel Weggenmann  Faseeh Fawad  Nimra Khalid  Faisan Sabir  Ahsan Jamal Khan 《Natural Hazards》2017,87(2):757-771

This paper presents laboratory experiments and numerical simulations of effects of submerged obstacles on tsunami-like solitary wave and its run-up. This study was carried out for the breaking and non-breaking solitary waves on 1:19.85 uniform slope which contains a submerged obstacle. New laboratory experiments are performed to describe the mitigation of tsunami amplitude and run-up under the effect of submerged obstacles. We are based on experimental results obtained to validate the numerical model. The numerical modeling using COULWAVE aims essentially to show the effect of the obstacle on the shape of solitary wave and the limit of this effect. Using a multiple nonlinear regression, we have determined a model to estimate height of run-up according to the amplitude of the wave and the obstacle peak depth.  相似文献   

Colluvial and alluvial sediment archives temporally resolved by OSL dating: Implications for reconstructing soil erosion     

M. Fuchs  M. Fischer  R. Reverman 《Quaternary Geochronology》2010,5(2-3):269-273

Colluvial and alluvial sediments represent important geoarchives to reconstruct long-term soil erosion and to gain insight into the complex system of sediment cascades and sediment fluxes within a catchment. In this respect, the temporal information of sediment archive formation is essential and achievable through optical stimulated luminescence (OSL) dating. In this study, colluvial and alluvial sediments from a mesoscale catchment in northern Bavaria were investigated and dated by OSL. Insufficient sediment bleaching was detected for some of the samples. In these cases, the method proposed by Fuchs and Lang [Fuchs, M., Lang, A., 2001. OSL dating of coarse-grain fluvial quartz using single-aliquot protocols on sediments from NE Peloponnese, Greece. Quaternary Science Reviews 20, 783–787.] was applied for equivalent dose (D_e) determination. The calculated OSL ages are in stratigraphic order and their accuracy is confirmed by ¹⁴C age control. Based on the chronostratigraphies for alluvial and colluvial archives, there is a dominant synchronous sedimentation history for the Medieval and Modern period, but initiation of Holocene sedimentation occurred at different times in the upper and lower parts of the catchment. The latter phenomenon might be explained by the decoupled sediment fluxes between both the slope–channel system and the upper and lower catchment.  相似文献   

Spatial scan statistics in vulnerability assessment: an application to mountain hazards   总被引：4，自引：2，他引：2  

Sven Fuchs  Christine Ornetsmüller  Reinhold Totschnig 《Natural Hazards》2012,64(3):2129-2151

In the European Alps, the concept of risk has increasingly been applied in order to reduce the susceptibility of society to mountain hazards. Risk is defined as a function of the magnitude and frequency of a hazard process times consequences; the latter being quantified by the value of elements at risk exposed and their vulnerability. Vulnerability is defined by the degree of loss to a given element at risk resulting from the impact of a natural hazard. Recent empirical studies suggested a dependency of the degree of loss on the hazard impact, and respective vulnerability (or damage-loss) functions were developed. However, until now, only little information is available on the spatial characteristics of vulnerability on a local scale; considerable ranges in the loss ratio for medium process intensities only provide a hint that there might be mutual reasons for lower or higher loss rates. In this paper, we therefore focus on the spatial dimension of vulnerability by searching for spatial clusters in the damage ratio of elements at risk exposed. By using the software SaTScan, we applied an ordinal data model and a normal data model in order to detect spatial distribution patterns of five individual torrent events in Austria. For both models, we detected some significant clusters of high damage ratios, and consequently high vulnerability. Moreover, secondary clusters of high and low values were found. Based on our results, the assumption that lower process intensities result in lower damage ratios, and therefore in lower vulnerability, and vice versa, has to be partly rejected. The spatial distribution of vulnerability is not only dependent on the process intensities but also on the overall land use pattern and the individual constructive characteristics of the buildings exposed. Generally, we suggest the use of a normal data model for test sites exceeding a minimum of 30 elements at risk exposed. As such, the study enhanced our understanding of spatial vulnerability patterns on a local scale.  相似文献   

Vulnerability assessment in natural hazard and risk analysis: current approaches and future challenges   总被引：10，自引：9，他引：1  

Sven Fuchs  J?rn Birkmann  Thomas Glade 《Natural Hazards》2012,64(3):1969-1975

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Editorial for the special issue: vulnerability to natural hazards—the challenge of integration   总被引：8，自引：6，他引：2  

Sven Fuchs  Christian Kuhlicke  Volker Meyer 《Natural Hazards》2011,58(2):609-619

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