Interferometric imaging of multiples in an RTM approach

It is well known that reverse-time migration is capable of correctly imaging multiply scattered energy. To do this, one of the interfaces from which the waves scatter must be included in the background velocity model. In a one-way framework this requirement is avoided by iteratively forming images of higher-order scattered waves. These techniques use an image made with singly scattered waves to estimate the locations of some of the reflection points in a multiply-scattered wave, from which the location of an additional scattering point is determined through standard imaging techniques. This removes the requirement that a single multiple-generating interface be identified. Here we extend this technique to reverse-time migration using results from several recent studies linking standard and extended imaging conditions to interferometry. This results in a method to generate images with multiply-scattered waves using the full-waveform imaging techniques of reverse-time migration and the iterative imaging formulations of scattering series in a one-way framework.Geo-Mathematical Imaging GroupTOTAL (Firm)Massachusetts Institute of Technology. Earth Resources Laborator

Seismic Imaging and Illumination with Internal Multiples

If singly scattered seismic waves illuminate the entirety of a subsurface structure of interest, standard methods can be applied to image it. It is generally the case, however, that with a combination of restricted acquisition geometry and imperfect velocity models, it is not possible to illuminate all structures with only singly scattered waves. We present an approach to use multiply scattered waves to illuminate structures not sensed by singly scattered waves. It can be viewed as a refinement of past work in which a method to predict artifacts in imaging with multiply scattered waves was developed. We propose an algorithm and carry out numerical experiments, representative of imaging of the bottom and flanks of salt, demonstrating the effectiveness of our approach.Dutch National Science Foundation (grant number NWO:VIVI865.03.007)StatoilHydroNorwegian Research Council (ROSE project)Geo-Mathematical Imaging Grou

Recursive Imaging with Multiply-Scattered Waves Using Partial Image Regularization: A North Sea Case Study

As more resources are directed toward reverse-time migration an accurate velocity model, including strong reflectors, is necessary to form a clear image of the subsurface. This is of particular importance in the vicinity of salt, where singly-scattered waves are often not ideal for imaging the salt flanks. This has led to interest in processing doubly-scattered waves (also called duplex or prismatic waves) for imaging salt flanks and thus improving the location of salt boundaries in a velocity model. We present a case study in which we use doubly-scattered waves in a two-pass one-way method to image salt flanks in a North Sea data set. By working in the one-way framework we are able to separately construct images with singly, doubly, and triply scattered waves. We illustrate a multi-step imaging process that includes multiply-scattered waves by using an imaged reflector to fix one (or more) of the scattering points, allowing for multiply-scattered energy from several reflectors, potentially with poor continuity, to be included without picking each reflector individually. With this method we are able to image the flank of a North Sea salt body.Norwegian State Oil CompanyNorwegian Research CouncilGeo-Mathematical Imaging GroupTOTAL (Firm)Massachusetts Institute of Technology. Earth Resources Laborator

Policy democracy? Social and material participation in biodiesel policy-making processes in India

Following its 2003 biodiesel mission, the Indian national government released its controversial policy on biodiesel in December 2009. Viewing the policy as a set of propositions that have been progressively assembled and constituted by many voices, we study its making on the basis of 72 qualitative interviews and ethnographic fieldwork. We consider the policy-making process to constitute policy democracy if its propositions were well-articulated. A well-articulated proposition is one that has registered the voices of many different human and nonhuman entities, including those that were hitherto mute. In addition, a well-articulated proposition must have allowed the entities to challenge and recompose it. And it must not have turned the entities’ actions and voices into a repetitive singularity. Finally, a well-articulated proposition is not easily transferrable between different socio-ecological situations. We argue that the Indian government attempted to perform policy democracy, by being partially responsive to some entities’ recalcitrance. However, it failed to register crucial voices associated with biodiesel production such as those of water and CO2. It also turned many voices into repetitive singularities, discounting the different relations that allow an entity to speak in multiple voices. The policy’s propositions remained easily transferrable between diverse socio-ecological situations, ignoring the immense diversity of India’s lands, their inhabitants and their practices associated with biodiesel production. Finally, due to a severe disconnect between the various voices registered in its different propositions, we argue that the policy lacked overall consistency

The politics of smart expectations: Interrogating the knowledge claims of smart mobility

This paper studies the performativity of smart mobility expectations in envisioning urban futures. Smart mobility, or ICT-enabled transport services, are increasingly considered a necessary ingredient for sustainability transitions in cities. Expectations of smart mobility’s contribution to such a transition are constituted by a strong belief in the transformative potential of data collection and use. These knowledge claims embedded in smart mobility expectations tend to be unchallenged, yet contribute to a particular future vision of urban mobility. Our empirical analysis, which draws on two empirical smart cycling case studies in Utrecht, the Netherlands, and Bordeaux, France, underlines the politics of such smart knowledge claims in two smart cycling projects and identifies distinct processes as to how such claims may shape and structure mobility futures. We observe intimate entanglements between what is being developed in terms of technologies and services; and the societal needs that the projects’ expectations promise to fulfil. At the same time, we witness a disentanglement of these interconnected knowledge claims when projects unfold, leaving the promise of (un)achieved societal benefits out of view. Indeed, smart knowledge claims carried strong inherent legitimacy in the cases studied, thereby risking to exclude non-smart alternatives