Improving Kirchhoff migration with repeated local plane-wave imaging? A SAR-inspired signal-processing approach in prestack depth imaging     

Isabelle Lecomte  Svein-Erik Hamran  Leiv-J. Gelius 《Geophysical Prospecting》2005,53(6):767-785

A local plane-wave approach of generalized diffraction tomography in heterogeneous backgrounds, equivalent to Kirchhoff summation techniques when applied in seismic reflection, is re-programmed to act as repeated synthetic aperture radar (SAR) imaging for seismic prestack depth migration. Spotlight-mode SAR imaging quickly provides good images of the electromagnetic reflectivity of the ground via fast Fourier transform (FFT)-based signal processing. By calculating only the Green's functions connecting the aircraft to the centre of the illuminated patch, scattering structures around that centre are also recovered. SAR technology requires us to examine seismic imaging from the local point of view, where the quantity and quality of the available information at each image point are what are important, regardless of the survey geometry. When adapted to seismics, a local image of arbitrary size and sampling is obtained by FFT of seismic energy maps in the scattering wavenumber domain around each node of a pre-calculated grid of Green's functions. These local images can be used to generate a classic prestack depth-migrated section by collecting only their centres. However, the local images also provide valuable information around the centre, as in SAR. They can therefore help to pre-analyse prestack depth migration efficiently, and to perform velocity analysis at a very low cost. The FFT-based signal-processing approach allows local, efficient and automatic control of anti-aliasing, noise and resolution, including optimized Jacobian weights. Repeated local imaging could also be used to speed up migration, with interpolation between local images associated with a coarse grid of Green's functions, as an alternative to interpolation of Green's functions. The local images may, however, show distortions due to the local plane-wave approximation, and the velocity variations across their frame. Such effects, which are not necessarily a problem in SAR, should be controlled and corrected to further enhance seismic imaging. Applications to realistic models and to real data show that, despite the distortion effects, the local images can yield similar information to prestack depth migration, including common-image-point gathers for velocity analyses and AVO/AVA effects, at a much lower cost when a small target is considered.  相似文献   

Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)     

Maryline Moulin  Daniel Aslanian  Jean-Louis Olivet  Isabelle Contrucci  Luis Matias  Louis Géli  Frauke Klingelhoefer  Hervé Nouzé  Jean-Pierre Réhault  Patrick Unternehr 《Geophysical Journal International》2005,162(3):793-810

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Stratigraphic architecture of the Plio-Pleistocene infill of the Corinth Rift: Implications for its structural evolution     

Sbastien Rohais  Rmi Eschard  Mary Ford  Franois Guillocheau  Isabelle Moretti 《Tectonophysics》2007,440(1-4):5-28

An integrated study of the stratigraphy, structure, sedimentology, and geomorphology of the Akrata–Derveni region (southern coast of the Gulf of Corinth, Greece) forms the basis for a tectono-stratigraphic model for the evolution of the Plio-Pleistocene central Corinth Rift.

The syn-rift sediments exposed on the uplifted southern coast of the Gulf of Corinth comprise three stratigraphic groups. Maximum total thickness of the syn-rift sediments can reach 2800 m in the middle of the studied area. The Lower Group is made of fluvio-lacustrine deposits. The Middle Group corresponds to thick alluvial fan conglomerates and their equivalent Gilbert-type fan deltas that built toward the north. The Upper Group is composed of uplifted terrace deposits, slope breccias and small Gilbert-type deltas. These groups have been subdivided into informal formations and depositional systems. Restoration of the stratigraphic architecture along a N–S transect provides a linked structural and depositional model for this part of the rift. Reconstruction of the latest phases of uplift is based on a study of geomorphological features.

Evolutionary phases include, (1) an overall increase in accommodation space during deposition of the Lower and Middle Groups followed by (2) a drastic decrease in accommodation space during deposition of the Upper Group. Sedimentary signals indicate that most of the major normal faults were active during deposition of the Lower Group. The depocentre was located in the middle part of the study area and paleocurrents were predominantly toward the ENE. The main depositional system shifted south at the onset of deposition of the Middle Group, recording a widening and deepening of the rift. This major event also corresponds to a change in paleocurrent direction to a clear northward polarity. The southernmost border fault, the Killini Fault, was sealed during deposition of the Middle Group. A northward migration of fault activity was associated with northward progradation of giant Gilbert-type fan deltas that record water depths up to 500 m. Finally, the fan delta system was abandoned as progressive tilting to the south and uplift of the margin induced a reversal of the drainage system with the development of an endorheic depression. Sediment supply to the basin thus decreased and a forced regression took place during deposition of the Upper Group recording a northward shift of more than 5 km and a 600 m relative sea-level drop. As no major eustatic sea-level falls of such amplitude are documented during the Pleistocene, the uplift is linked to regional tectonics. Uplift and fault reactivation gave the present day configuration of the southern coast of the Gulf.  相似文献   

Rockglacier activity studies on a regional scale: comparison of geomorphological mapping and photogrammetric monitoring     

Isabelle Roer  Michael Nyenhuis 《地球表面变化过程与地形》2007,32(12):1747-1758

In their spatial distribution as well as in their different states of activity, rockglaciers imply important information on former and recent permafrost conditions. Two different methods were applied in one study area (Turtmann Valley, Swiss Alps) in order to compare their suitability in assessing rockglacier activity. The comparison of geomorphological mapping and photogrammetric monitoring demonstrated a good accordance, especially on a regional scale. On a local scale, some differences in delimitation of the landforms as well as in the degree of activity were found. One reason for the observed differences is the qualitative character of geomorphological mapping resulting from the variable suitability of single parameters and combinations thereof in the determination of rockglacier activity. Based on these results, geomorphological mapping of rockglaciers can be improved by data from photogrammetric monitoring. Therefore, at best the two methods are combined when analysing former and present permafrost distribution. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Short-term measures for the control of ozone peaks: expertise from CTM simulations     

Fanny Lasry  Isabelle Coll  Sylvain Fayet  Maxime Havre  Robert Vautard 《Journal of Atmospheric Chemistry》2007,57(2):107-134

In Europe, in case of the observation or the forecast of a photochemical event, punctual and local reductions in anthropogenic emissions can be triggered at the regional scale. Although the necessity for the establishment of such measures appears to be justified by bad air quality records over large European cities, individual short-term action plans (STAPs) have been blindly elaborated by regional authorities. Moreover, as they impose industrial and road traffic emission restrictions, these measures have an elevated economical cost. It is consequently crucial to determine their efficiency and potential for ozone peak reduction. The study presented in this paper aims to draw up an expertise on standard European STAPs, through the example of a French Mediterranean city. The objective is to determine and investigate the impact of current STAPs on ozone peak formation and to test ways to optimise their efficiency. In this frame, a set of emission scenarios has been elaborated and tested with the chemistry-transport model CHIMERE on the Berre–Marseille area. Simulations have shown that the tested action plans are not sufficient to eradicate severe ozone peaks and that more drastic restrictions on emissions are required to significantly affect ozone plumes. However, results also showed that the potential for ozone reduction remains small, with a maximum impact of only 5 ppbv for feasible STAPs. Finally, a temporal analysis of the ozone-emission relationship was engaged in order to optimise their application.  相似文献   

Deep structure of the West African continental margin (Congo, Zaïre, Angola), between 5°S and 8°S, from reflection/refraction seismics and gravity data     

Isabelle Contrucci  Luis Matias  Maryline Moulin  Louis Géli  Frauke Klingelhofer  Hervé Nouzé  Daniel Aslanian  Jean-Louis Olivet  Jean-Pierre Réhault  Jean-Claude Sibuet 《Geophysical Journal International》2004,158(2):529-553

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Response Surface Designs for Scenario Management and Uncertainty Quantification in Reservoir Production   总被引：1，自引：0，他引：1  

Astrid Jourdan  Isabelle Zabalza-Mezghani 《Mathematical Geology》2004,36(8):965-985

Response surface experimental designs provide a framework for evaluating sensitivities and assessing uncertainties in reservoir-production forecasts for continuous parameters (i.e. permeability, flow rate, etc.). In this paper, the method is extended in order to integrate both continuous and discrete parameters (i.e. fault status: open/close, injection scheme: SWAG/WAG, etc.). This paper presents an appropriate experimental designs approach, notably the regression models associated with, and the statistical interpretation (sensitivity study, Monte Carlo simulations, etc.). The method has been successfully applied to a reservoir oil-production simulation problem. The objective was to define the best production scheme by optimizing the well-completion level. This application has highlighted the advantages of this new approach, both in terms of decreasing simulation cost and improving the interpretation quality.  相似文献   

Sismique marine haute résolution 3D : un nouvel outil de reconnaissance à destination de la communauté scientifique     

Yannick Thomas  Bruno Marsset  Stéphane Didailler  Jean-Pierre Regnault  Sandie Le Conte  Dominique Le Roux  Patrick Farcy  Maurice Magueur  Pascal Viollette  Jacques Herveou  Jean-Charles Guedes  Bernard Jegot  Gilles Gascon  Christian Prud&#x;homme  Hervé Nouze  Estelle Thereau  Isabelle Contrucci  Jean-Paul Foucher 《Comptes Rendus Geoscience》2004,336(6):579-585

This note presents the first results of the development of 3D high-resolution marine seismic method designed for scientific application. A particular attention was paid to the realisation of an operational system to be in agreement with the expected goals in term of acquisition and processing. To cite this article: Y. Thomas et al., C. R. Geoscience 336 (2004).  相似文献   

Compartmentalisation of fluid migration pathways in the sub-Andean Zone, Bolivia     

Isabelle Moretti  Pierre Labaume  Simon M. F. Sheppard  Jacques Boulgue 《Tectonophysics》2002,348(1-3)

Numerous observations indicate that faults play a major role on the migration pathways of fluids in the Bolivian sub-Andean Zone. Most oil seeps in the foothills are located on faults, but oil fields in the foredeep are closed by faults. In the foothills, analysis of cements in fractures inside and around fault zones indicates that the faults act as barriers for transversal migration but can be preferential lateral migration pathways for both hydrocarbons and water. A detailed study of these apparent contradictions suggests that the hydraulic behaviour of faults changes with depth in relation with sandstone diagenesis, but it is strain-independent. From microstructural analyses of fault zones, we suggest that the main controlling factor is temperature, which facilitates or inhibits quartz precipitation. This result implies that the same fault is a barrier for lateral and transversal migration at depths >3 km, due to sealing of fractures by authigenic quartz at T>80 °C, and is a lateral drain in its shallower parts. As a result, the various thrust sheets are isolated from a hydraulic point of view, whereas migration in the foreland may take place over long distances (>100 km).  相似文献   

Thermal regime of fold and thrust belts—an application to the Bolivian sub Andean zone     

Laurent Husson  Isabelle Moretti 《Tectonophysics》2002,345(1-4)

A quantitative analysis of the various parameters influencing the thermal regime in orogenic belts and related foredeeps shows that (i) the increasing heat flow in internal zones is mainly due to the thickening of radiogenic layers, although there is no simple proportionality between crustal thickness and heat flow signal at large scale; (ii) in external zones, where the horizontal strain rate is large (such as in the Bolivian Andes), surface processes can be of first order within the first kilometers of the crust. Hence, they induce a large scatter in the thermal data which are acquired at shallow depths. The deep thermal regime can be restored only by a quantitative assessment of these parameters. Active erosion (respectively sedimentation) can increase (resp. reduce) the heat flow by a factor of 2 in the uppermost kilometers. The effects of fluid circulation percolating at depth can also generate significant local disturbances. Other processes such as heat advection during thrusting, surface morphology and climate change have a minor influence in most settings, compared to the aforesaid effects.In the Bolivian Sub Andean Zone, between 18°S and 22°S, the very active deformation enhances the surface thermal perturbations (particularly erosion and sedimentation) and disturb the thermal field. The analysis of these data accounting for the kinematics of the belt allows the lateral variations of the thermal regime at various scales to be assessed. A slight eastward increase in the thermal regime towards the Chaco plain is evidenced as well as towards the Boomerang area, as the Mesozoic and Cenozoic sedimentary cover gets thinner.  相似文献