Crustal anisotropy in southwest Ireland from analysis of controlled source shear-wave data     

P.W. Readman  F. Hauser  B.M. O'Reilly  V.C. Do   《Tectonophysics》2009,474(3-4):571-583

Results from a travel-time analysis of three-component shear-wave (S-wave) data recorded in southwest Ireland during a controlled source seismic experiment have been used to investigate the magnitude of crustal anisotropy. The data used were recorded from 20 in-line shots on three-component short-period stations deployed at approximately 1-km spacing along two parallel profiles. Analysis of the travel-time differences between vertically and horizontally polarised S-waves recorded on vertical, radial and transverse seismometer components was undertaken using seismic phases travelling near the Earth's surface (S_g) and reflected from the Moho (S_mS). Travel-time differences between the components for both phases scatter largely within the range ± 0.2 s, which is about the uncertainty in the measurements, with no observed coherent variation with shot-receiver offset. Synthetic S-wave seismograms were also computed from 1-D S-wave velocity models with varying degrees of anisotropy in the upper and in the lower crusts. Travel-time differences of S_g and S_mS phases picked from these synthetic seismograms confirm that for anisotropies with probable symmetries of magnitude 1–2% in either the upper or lower crust should result in an observable variation of the travel-time differences between the transverse and radial, and transverse and vertical components with source–receiver offset. The study shows that crustal anisotropy does not contribute significantly to the marked anisotropy recently deduced from SKS and SKKS measurements in Ireland, which is therefore confirmed to reside at sub-crustal and deeper mantle levels.  相似文献   

Occurrence of gorgosterol in diatoms of the genus Delphineis     

Sebastiaan W. Rampen  John K. Volkman  Sung Bum Hur  Ben A. Abbas  Stefan Schouten  Ian D. Jameson  Daniel G. Holdsworth  Jean Hee Bae  Jaap S. Sinninghe Damsté 《Organic Geochemistry》2009,40(1):144-147

The presence of the C₃₀ sterol gorgosterol (22,23-methylene-23,24-dimethylcholest-5-en-3ß-ol) and its analogues in some marine and freshwater environments is generally associated with invertebrate animals or dinoflagellates since there have been no reports of them in other microalgal classes. Here we show that two unialgal cultures of different species of the marine diatom Delphineis contain gorgosterol in addition to sterols more commonly found in diatoms. Our findings suggest that some reports of gorgosterol in seawater and marine sediments may well have an origin, at least in part, from diatoms.  相似文献   

Fish and ostracod remains from the Santos Basin (Cretaceous to Recent), Brazil     

C. Giles Miller  Martha Richter  Dermeval A. Do Carmo 《Geological Journal》2002,37(4):297-316

For the first time, ichthyoliths are described from the Santos sedimentary basin, offshore southern Brazil. Isolated teeth, dermal scales and the first documented otoliths from Cretaceous (Albian) to Recent cuttings from five wells are described. The following groups are represented: Chondrichthyans: Triakidae, Carcharhinidae; Ginglymostomatidae: ?Ginglymostoma sp., Lamnidae indet., Scyliorhinidae; Osteichthyans: Teleostei; Myctophiidae: Diaphus aff. splendidus sp. complex, Diaphus spp., Diaphus cf. garmani, Ceratoscopelus aff. warmingii; Sternoptychidae: Valenciennellus tripunctulatus, teeth of indeterminate Teleostei. The majority of these ichthyofossils represent extant forms, known to occur in the Atlantic Ocean, and are of potential value for stratigraphical correlations between oil‐yielding basins in the region. Ostracods are not well preserved but can be identified to generic level indicating marine environments. The ostracod faunas offer potential for intrabasinal correlation in the Eocene and Oligocene. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Factors affecting the stability of deep excavations in clay with consideration of a full elastoplastic support system     

Do  Tuan-Nghia  Ou  Chang-Yu 《Acta Geotechnica》2020,15(7):1707-1722

Acta Geotechnica - This study investigates the stability of internally braced excavations in thick, saturated clay using a finite element method with reduced shear strength. The support system was...  相似文献   

Numerical study on the interaction among a nonlinear wave,composite breakwater and sandy seabed     

Dong-Soo Hur  Chang-Hoon Kim  Jong-Sung Yoon 《Coastal Engineering》2010

Most previous investigations related to composite breakwaters have focused on the wave forces acting on the structure itself from a hydrodynamic aspect. The foundational aspects of a composite breakwater under wave-induced cyclic loading are also important in studying the stability of a composite breakwater. In this study, numerical simulations were performed to investigate the wave-induced pore water pressure and flow changes inside the rubble mound of the composite breakwater and seabed foundation. The validity and applicability of the numerical model were demonstrated by comparing numerical results with existing experimental data. Moreover, the present model clearly has shown that the instantaneous directions of pore water flow motion inside the seabed induced by surface waves are in good agreement with the general wave-induced pore water flow inside the seabed. The model is further used to discuss the stability of a composite breakwater, i.e., the interaction among nonlinear waves, composite breakwater and seabed. Numerical results suggest that the stability of a composite breakwater is affected by not only downward shear flow generating on the seaward slope face of the rubble mound but, also, a high and dense pore water pressure gradient inside the rubble mound and seabed foundation.  相似文献   

Effects of warming on microbial communities in the coastal waters of temperate and subtropical zones in the Northern Hemisphere,with a focus on Gammaproteobacteria     

Dao Thi Anh Tuyet  Toshinari Tanaka  Rumi Sohrin  Do Manh Hao  Kazuyo Nagaosa  Kenji Kato 《Journal of Oceanography》2015,71(1):91-103

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Dynamics of fluid-saturated soils—variational formulation     

Ranbir S. Sandhu  Soon J. Hong 《国际地质力学数值与分析法杂志》1987,11(3):241-255

Variational principles governing dynamics of fluid-saturated linear elastic porous media are derived. Complementary as well as direct formulations are discussed. Discontinuities in the field variables, the approximation space and the excitation are allowed for. Extensions of the variational principles to relax smootheness requirements on certain field variables are introduced along with some specizalizations convenient for finite element applications.  相似文献   

Three-dimensional numerical simulation for mechanized tunnelling in soft ground: the influence of the joint pattern   总被引：1，自引：1，他引：0  

Ngoc-Anh Do  Daniel Dias  Pierpaolo Oreste  Irini Djeran-Maigre 《Acta Geotechnica》2014,9(4):673-694

The main purpose of this study was to provide a three-dimensional numerical model, which would allow the tunnel lining behaviour and the displacement field surrounding the tunnel to be evaluated. Most of the processes that occur during mechanized excavation have been simulated in this model. The influence of the lining joint pattern, including segmental lining joints and their connections, has in particular been taken into consideration. The impact of the processes during mechanized excavation, such as the grouting pressure and the jacking forces in the structural forces induced in the tunnel lining, has been presented. These values depend on the tunnel advancement. However, a negligible influence of the joint pattern on the ground displacement field surrounding the tunnel has been observed. Generally, a variation in the structural forces in successive rings along the tunnel axis has been found in a staggered segmental lining, indicating the necessity of simulating the joints in the tunnel lining and using a full three-dimensional numerical model to obtain an accurate estimation. In addition, the considerable influence of the coupling effect between successive rings on the lining behaviour has been highlighted.  相似文献   

Anharmonic and standing dynamo waves: theory and observation of stellar magnetic activity     

S. Baliunas  P. Frick  D. Moss  E. Popova  D. Sokoloff  W. Soon 《Monthly notices of the Royal Astronomical Society》2006,365(1):181-190

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Testing a conceptual hillslope recession model based on the storage–discharge relationship with the Richards equation     

Do‐Hun Lee 《水文研究》2007,21(23):3155-3161

The conceptual recession model based on the storage–discharge relationship was proposed to account for the unsaturated–saturated water storage interaction. The recession model was formulated by combining the constitutive storage–discharge relationship with the integral balance equation for unsaturated and saturated water storage. The functional form of the constitutive storage–discharge relationship was determined from the spatial integration of the Richards equation. The performance of the recession model was tested by comparing with the solution of the Richards equation for different simulation geometric shapes and soil types. The conceptual recession model incorporating the unsaturated–saturated water storage interaction was in good agreement with the recession response of the Richards equation. However, the recession model that neglected the unsaturated–saturated water storage interaction was comparable to the Richards equation only for soils with the weak interaction between unsaturated water storage and saturated water storage. This result suggests the important role of the unsaturated–saturated water storage interaction in the formulation of the recession process when the derivative of the functional relationship between the unsaturated water storage and saturated water storage becomes significant. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献