High‐resolution multi‐component distributed acoustic sensing          下载免费PDF全文

Ivan Lim Chen Ning  Paul Sava 《Geophysical Prospecting》2018,66(6):1111-1122

Distributed acoustic sensing uses an optical fibre together with an interrogator unit to perform strain measurements. The usage of distributed acoustic sensing in geophysics is attractive due to its dense spatial sampling and low operation cost if the optical fibre is freely accessible. In the borehole environment, optical fibres for distributed acoustic sensing are often readily available as a part of other sensing tools, such as for temperature and pressure. Although the distributed acoustic sensing system promises great potential for reservoir monitoring and surface seismic acquisition, the single axial strain measurement of distributed acoustic sensing along the fibre is inadequate to fully characterise the different wave modes, thus making reservoir characterisation challenging. We propose an acquisition system using five equally spaced helical optical fibres and a straight optical fibre to obtain six different strain projections. This system allows us to reconstruct all components of the 3D strain tensor at any location along the fibre. Analysing the condition number associated with the geometry of the optical fibre, we can systematically search for the optimum design parameters for our configuration. Numerical examples demonstrate the effectiveness of our proposed method to successful reconstruction of the full strain tensor from elastic wavefields of arbitrary complexity.  相似文献   

Numerical modelling of reinforced‐concrete structures under seismic loading based on the finite element method with discrete inter‐element cracks          下载免费PDF全文

Željana Nikolić  Nikolina Živaljić  Hrvoje Smoljanović  Ivan Balić 《地震工程与结构动力学》2017,46(1):159-178

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Target-oriented imaging using extended image volumes: a low-rank factorization approach     

Rajiv Kumar  Marie Graff  Ivan Vasconcelos  Felix J. Herrmann 《Geophysical Prospecting》2019,67(5):1312-1328

Imaging in geological challenging environments has led to new developments, including the idea of generating reflection responses by means of interferometric redatuming at a given target datum in the subsurface, when the target datum lies beneath a complex overburden. One way to perform this redatuming is via conventional model-based wave-equation techniques. But those techniques can be computationally expensive for large-scale seismic problems since the number of wave-equation solves is equal to two times the number of sources involved during seismic data acquisition. Also conventional shot-profile techniques require lots of memory to save full subsurface extended image volumes. Therefore, we can only form subsurface image volumes in either horizontal or vertical directions. To exploit the information hidden in full subsurface extended image volumes, we now present a randomized singular value decomposition-based approach built upon the matrix probing scheme, which takes advantage of the algebraic structure of the extended imaging system. This low-rank representation enables us to overcome both the computational cost associated with the number of wave-equation solutions and memory usage due to explicit storage of full subsurface extended image volumes employed by conventional migration methods. Experimental results on complex geological models demonstrate the efficacy of the proposed methodology and allow practical reflection-based extended imaging for large-scale five-dimensional seismic data.  相似文献   

Zircon U–Pb geochronology,major-trace elements and Sr–Nd isotope geochemistry of Mashhad granodiorites (NE Iran) and their mafic microgranular enclaves: evidence for magma mixing and mingling     

Maryam Deyhimi  Ali Kananian  Fatemeh Sepidbar  Ivan Vlastelic  Jean-Louis Paquette 《International Geology Review》2020,62(13-14):1615-1634

ABSTRACT

Mashhad granitoids and associated mafic microgranular enclaves (MMEs), in NE Iran record late early Mesozoic magmatism, was related to the Palaeo-Tethys closure and Iran-Eurasia collision. These represent ideal rocks to explore magmatic processes associated with Late Triassic closure of the Palaeo-Tethyan ocean and post-collisional magmatism. In this study, new geochronological data, whole-rock geochemistry, and Sr–Nd isotope data are presented for Mashhad granitoids and MMEs. LA–ICP–MS U–Pb dating of zircon yields crystallization ages of 205.0 ± 1.3 Ma for the MMEs, indicating their formation during the Late Triassic. This age is similar to the host granitoids. Our results including the major and trace elements discrimination diagrams, in combination with field and petrographic observations (such as ellipsoidal MMEs with feldspar megacrysts, disequilibrium textures of plagioclase), as well as mineral chemistry, suggest that MMEs formed by mixing of mafic and felsic magmas. The host granodiorite is a felsic, high K calc-alkaline I-type granitoid, with SiO₂ = 67.5–69.4 wt%, high K₂O (2.4–4.2 wt%), and low Mg# (42.5–50.5). Normalized abundances of LREEs and LILEs are enriched relative to HREEs and HFSEs (e.g. Nb, Ti). Negative values of whole-rock εNd_(t) (?3 to ?2.3) from granitoids indicate that the precursor magma was generated by partial melting of enriched lithospheric mantle with some contributions from old lower continental crust. In the MMEs, SiO₂ (53.4–58.2 wt%) is lower and Ni (3.9–49.7 ppm), Cr (0.8–93.9 ppm), Mg# (42.81–62.84), and εNd_(t) (?2.3 to +1.4) are higher than those in the host granodiorite, suggesting a greater contribution of mantle-derived mafic melts in the genesis of MMEs.  相似文献   

Dr Donald S McLusky – an appreciation and thanks from ECSS     

Eric Wolanski Ivan Valiela  Mike Elliott 《Estuarine, Coastal and Shelf Science》2010

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Anisotropy of P-wave Velocity in the Upper Crust of the Central External Dinarides     

Lokmer  Ivan  Herak  Marijan 《Studia Geophysica et Geodaetica》1999,43(4):345-356

The anisotropy of Pg-wave velocity in the area of the central External Dinarides is measured by using arrival time data as reported by local and regional seismological stations. The observed velocity varies between 5.73 km/s (in the ESE-WNWdirection) and 6.20 km/s (in the SSW-NNE direction), indicating azimuthal anisotropy with symmetry axis azimuths of 23°±n 90°. These closely match the orientation of the principal stress axes in the region, as revealed by analyses of available fault-plane solutions. The observed anisotropy may be modelled by assuming a system of vertical/subvertical cracks in the upper crust, aligned under the influence of the regional tectonic stress field.  相似文献   

Dynamical state of superclusters of galaxies: do superclusters expand or have they started to collapse?     

Mirt Gramann  Ivan Suhhonenko 《Monthly notices of the Royal Astronomical Society》2002,337(4):1417-1425

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Summaries of presentations during the sixth Workshop of the International Association of Phytoplankton Ecology and Taxonomy,Mondsee, Austria, 15–25 September 1986     

H. R. Bürgi  Gerhild Deisinger  M. Dokulil  Barbara Hickel  Utsa Pollingher  Hedy Kling  Pertti Eloranta  Eugen Rott  Peter Pfister  Maria Moustaka  Ivan S. Heaney  Eugen Rott  A. E. Bailey-Watts  Jorgen Kristiansen  Asbjorn Skogstad 《Aquatic Sciences - Research Across Boundaries》1987,49(3):375-392

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Radiochemical Determination of Gold in Rocks     

Evgeny TASKAEV  Ivan PENEV  Hubert SCHELHORN  Martin GEISLER 《Geostandards and Geoanalytical Research》1987,11(1):103-106

A method developed for radiochemical determination of gold in rock samples has been applied to six Bulgarian, four ZGI (GDR) and one USGS geostandards. The method is based on acid dissolution of the sample, followed by extraction of gold with copper diethyldithiocarbamate solution in CHCl₃. The chemical yield was determined by using ¹⁹⁹Au tracer. The present data are compared with published values for the ZGI and USGS samples.  相似文献   

Kinematics of refracted and reflected waves in inhomogeneous media with non-planar interfaces     

Ivan Pšenčík  Reviewer V. Červený 《Studia Geophysica et Geodaetica》1972,16(2):126-152

Zusammenfassung Es werden die Grundbeziehungen für die Berechnung von Strahlen seismischer Wellen in inhomogenen Milieus abgeleitet, in denen die Geschwindigkeit allgemein von drei krummlinigen Koordinaten abhängt. Die angeführten Beziehungen stellen ein System von gewöhnlichen Differentialgleichungen erster Ordnung dar. Die numerische Lösung dieses Systems bietet eine Möglichkeit, die Strahlendiagramme, Laufzeitkurven und Isochronen für die gegebenen Geschwindigkeitsmodelle zu konstruieren. Aufmerksamkeit wird ebenfalls dem Einfall der Strahlen auf eine unebene Grenzschicht gewidmet. Die Beziehungen für die Berechnung reflektierter und refraktierter Strahlen werden abgeleitet. Anhand der abgeleiteten Beziehungen werden Strahlendiagramme und Laufzeitkurven für eine Geschwindigkeitsverteilung berechnet, die durch die vorläufige Interpretation der Ergebnisse von seismischen Tiefensondierungen am tschechoslowakischen Teil des Profils VI gewonnen wurden.  相似文献