Alessandra Ribodetti

Alessandra Ribodetti
Laboratoire Géoazur · Université de Nice Sophia-Antipolis

PhD in Applied Geophysics, HDR

About

121
Publications
26,337
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2,043
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Introduction
She received an MSc. in applied mathematics at the University of Genoa (IT) and a PhD in applied geophysics at the University of Nice-Sophia Antipolis (FR). During 1998-2000 she was a postdoctoral fellow at the Ecole des Mines de Paris (Marie Curie Research Training Grant). In 2000 she had a place as a research geophysicist at the IRD, Université de Nice-Sophia Antipolis (FR).
Additional affiliations
October 2000 - November 2015
Laboratoire Géoazur
Position
  • Researcher
January 1994 - October 2012
Observatoire Océanologique de Villefranche sur Mer
Position
  • Researcher
Description
  • I spent a part of my PhD thesis at Observatoire Océanologique de Villefranche sur Mer (Geoazur, Geomer team). I had a position as scientist at the IRD at the Geoazur in Villefranche-sur-mer until october 2013. I then moved in Sophia-Antipolis.

Publications

Publications (121)
Article
First-arrival traveltime tomography is one of the most used velocity model building techniques especially in sparse wide-angle acquisitions for deep crustal seismic imaging cases. Relying on the inversion of a picked attribute, the absolute traveltimes, the approach is ill-posed in terms of non-uniqueness of the solution. The latter is remedied by...
Article
We revisit the hypocentre-velocity problem, which is of interest in different fields as for example microseismics and seismology. We develop a formulation based on kinematic migration of two picked kinematic attributes in the two dimensional case, the traveltime and the slope (horizontal component of the slowness vector), from which we are able to...
Conference Paper
Full-text available
Ultra-long offset seabed acquisitions implemented with sparse array of ocean bottom nodes (OBN) are emerging as the go-to strategy for velocity model building. These stationary-recording geometries provide the flexibility to record a plethora of wave arrivals and in particular diving waves that undershoot the deepest targeted structures. These seab...
Conference Paper
We revisit the hypocenter-velocity problem which is of interest in different fields as for example microseismics and seismology. We show how, through a formulation based on kinematic migration focusing using two picked kinematic attributes in the two-dimensions case, the travel time and the slope (horizontal component of the slowness vector), we ar...
Article
Full-text available
The north Ligurian margin is a complex geological area in many ways. It has witnessed several phases of highly contrasting deformation styles, at both crustal scale and that of shallower cover tectonics, simultaneously or in quick succession, and with significant spatial variability. This complex interplay is mirrored in the resulting intricate str...
Conference Paper
Crustal-scale investigations through active seismic approaches presumptively yield the most structure resolving images. In practice, however, case studies reveal that we are far from the optimal resolution. The latter is not only caused by the geological complexity but mainly the challenges encountered at stages ranging from the survey design to th...
Conference Paper
In the last decade, seismic imaging below salt/basaltic bodies proved beyond doubt to be the most challenging task using conventional strategies in terms of surveying, processing and inversion. Recent innovations across the whole workflow pushed further the resolution limit in such complex environments for resource exploration purposes. On the othe...
Conference Paper
Ultra-long offset stationary-receiver acquisitions implemented with multi-component Ocean Bottom Nodes (OBN) are emerging as a suitable technology for deep offshore subsalt imaging by full waveform inversion (FWI). Ultra-long offsets allow to undershoot the deepest targeted structures with diving waves. In this framework, first-arrival traveltime +...
Article
Full-text available
Velocity macro-model building is an essential step of the seismic imaging workflow. Indeed, obtaining acceptable results through migration or full waveform inversion is highly dependent on the kinematic accuracy of the background/initial velocity model. Two decades ago, stereotomography was proposed as an alternative to reflection traveltime tomogr...
Conference Paper
Seismic tomography seeks to reconstruct the subsurface parameters, mainly wavespeeds. In reflection/diffraction tomography, an additional parameter class is inherently introduced: the scattering positions. The underlying inverse problem is awkward due to the ill-famed velocity-position coupling. We review different optimization strategies in the f...
Conference Paper
Full-text available
First-arrival traveltime tomography (FATT) has been one of the commanding tomographic approaches for long wavelength velocity model building. Nowadays, FATT models are often used as initial models for more resolving imaging methods such as full-waveform inversion (FWI). In this context, improving the accuracy of FATT model is crucial to mitigate th...
Conference Paper
Full-text available
Dense acquisition are more and more available in exploration and earthquake seismology. Tomographic approaches can now consider not only travel times but also the wavefront itself across the seismic network (Zhang and Thurber, 2003; Yuan et al., 2016). For dense controlled-source seismic experiments, double differences of travel times between recei...
Article
Full-text available
Slope tomography uses traveltimes, source, and receiver slopes of locally coherent events to build subsurface velocity models. Locally coherent events by opposition to continuous reflections are suitable for semiautomatic and dense picking, which is conducive to better resolved tomographic models. These models can be further used as background/init...
Presentation
Full-text available
Reconstructing the crustal properties from seismic data can rely on traveltimes and source/receiver slopes when dense acquisition is available for common source gather or common receiver gather as long as volumetric event pciking is achievable: with these extracted data, least-squares misfit optimization is performed based on linearized approximati...
Conference Paper
Full-text available
A new formulation for first arrival traveltime tomography is introduced based on the traveltime and slopes of first arrival local coherent events for 2D TTI media. Here, we use Eikonal solvers in forward modeling to calculate slope and traveltime of events, while taking advantage of adjoint state method to design a matrix-free framework for the inv...
Conference Paper
Full-text available
Depth velocity macro-model building is an essential step of the seismic imaging workflow. Indeed, obtaining acceptable results through migration or full waveform inversion is highly dependent on the initial background velocity model. Two decades ago, stereotomography was proposed as an alternative to more conventional methods like traveltime tomogr...
Conference Paper
Full-text available
For macro-velocity-model building, the ray-based formulation of classic stereotomography is replaced by eikonal solvers with simultaneous introduction of adjoint-state method for an efficient matrix free optimization scheme. In this approach, named adjoint stereotomography, forward modelling is performed from sources and receivers, making the appro...
Preprint
Full-text available
The Campo-Kribi subbasin is part of the Cameroon Atlantic rifted Margin. Detailed analysis of long offset pre-stack depth migrated seismic lines coupled with boreholes data enabled mapping of the Jurassic Early-Cretaceous fan-delta system at approximately 10 km southwest of the Kribi-Batanga oil and gas field. The fan is up to 25 km wide, 4km thick...
Article
Full-text available
Velocity macromodel building is a crucial step in the seismic imaging workflow as it provides the necessary background model for migration or full waveform inversion. In this study, we present a new formulation of stereotomography that can handle more efficiently long-offset acquisition, complex geological structures and large-scale data sets. Ster...
Article
Full-text available
Whether subducted oceanic reliefs such as seamounts promote seismic rupture or aseismic slip remains controversial. Here, we use swath bathymetry, pre-stack-depth-migrated multichannel seismic reflection lines and wide-angle seismic data collected across the Central Ecuador subduction segment to reveal a broad ~55-km x 50-km, ~ 1.5-2.0-km-high, low...
Article
Full-text available
A bridge is highlighted between the direct inversion and the indirect inversion. They are based on fundamental different approaches: one is looking after a projection from the data space to the model space while the other one is reducing a misfit between observed data and synthetic data obtained from a given model. However, it is possible to obtain...
Conference Paper
Full-text available
Stereotomography is a slope tomography based upon semi-automatic picking of local coherent events for estimating velocity macromodels from seismic reflection data. Its most widespread implementation relies on ray tracing for slope and traveltime computations and the explicit building of the so-called Fréchet derivative matrix for solving the invers...
Article
Full-text available
Extracting detailed earth information from an ensemble of seismic traces is a challenge facing full-waveform inversion. So far, success on synthetic and real data has been accomplished primarily for the twin purposes of complex structural imaging and geologic interpretation. An ongoing issue for the seismic-imaging community, in addition to buildin...
Article
Full-text available
At the North-Ecuadorian convergent margin (1°S–1.5°N), the subduction of the rough Nazca oceanic plate leads to tectonic erosion of the upper plate and complex seismogenic behavior of the megathrust. We used three selected pre-stack depth migrated, multi-channel seismic reflection lines collected during the SISTEUR cruise to investigate the margin...
Article
Full-text available
For the first time, a deep seismic data set acquired in the frame of the Algerian-French SPIRAL program provides new insights regarding the origin of the westernmost Algerian margin and basin. We performed a tomographic inversion of traveltimes along a 100-km-long wide-angle seismic profile shot over 40 ocean bottom seismometers offshore Mostaganem...
Conference Paper
Full-text available
We present an application of 3D frequency-domain full waveform inversion (FWI) on ocean-bottom cable data from the North Sea. Frequency-domain seismic modeling is performed in the visco-acoustic VTI approximation with a sparse direct solver based on the multifrontal method. The computational cost of the multifrontal LU factorization is efficiently...
Article
Full-text available
Computationally efficient 3-D frequency-domain full waveform inversion (FWI) is applied to ocean-bottom cable data from the Valhall oil field in the visco-acoustic vertical transverse isotropic (VTI) approximation. Frequency-domain seismic modelling is performed with a parallel sparse direct solver on a limited number of computer nodes. A multiscal...
Conference Paper
Full-text available
We present an application of 3D VTI visco-acoustic frequency-domain full waveform inversion (FWI) based on sparse direct solver on wide-azimuth OBC data from the Valhall oil field. Mono-parameter inversion for the vertical wavespeed is applied to the hydrophone component in the 3.5-10Hz passband. Compared to reflection traveltime tomography, we sho...
Article
Full-text available
The computational burden of frequency-domain full-waveform inversion (FWI) of wide-aperture fixed-spread data is conventionally reduced by limiting the inversion to a few discrete frequencies. In this framework, frequency-domain seismic modeling is performed efficiently for multiple sources by solving the linear system resulting from the discretiza...
Conference Paper
Full-text available
Frequency-domain full waveform inversion (FWI) of fixed-spread data can be limited to a few discrete frequencies thanks to the redundant control of frequency and scattering angle on the wavenumber coverage. In this framework, 3D finite-difference frequency-domain seismic modeling can be efficiently performed for multiple sources in the visco-acoust...
Article
Full-text available
Building high-resolution models of several physical properties of the subsurface by multiparameter full waveform inversion (FWI) of multicomponent data will be a challenge for seismic imaging for the next decade. The physical properties, which govern propagation of seismic waves in visco-elastic media, are the velocities of the P- and S-waves, dens...
Article
Full-text available
In most geologic environments, accounting for anisotropy is necessary to perform acoustic full waveform inversion (FWI) of wide-azimuth and wide-aperture seismic data because of the potential dependence of wave speeds on the direction of the wave propagation. In the framework of multiparameter FWI, the subsurface parameterization controls the influ...
Article
Full-text available
It is necessary to account for anisotropy in full waveform inversion (FWI) of wide-azimuth and wide-aperture seismic data in most geologic environments, for correct depth positioning of reflectors, and for reliable estimations of wave speeds as a function of the direction of propagation. In this framework, choosing a suitable anisotropic subsurface...
Conference Paper
Full-text available
We apply 2D VTI acoustic FWI to wide-aperture OBC data from the Valhall field. Initial models for FWI are determined by VTI reflection traveltime tomography. Mono-parameter and multi-parameter VTI FWI are applied to the hydroacoustic component for reconstruction of seismic wavespeeds and Thomsen parameters, while density and attenuation are kept at...
Conference Paper
Bäcklund transform is applied to a seismogram in order to construct a new signal where the time is transformed in a pseudo-time the square of its dimension is expressed in seconds. The Bäcklund transform links partial differential equations related to wave propagation to partial differential equations related to diffusion. Potential applications ha...
Article
Full-text available
Tectonic processes that control the transition from poorly consolidated sediment entering the subduction channel (SC) to the seismogenic zone are documented using seismic imaging. We applied pre-stack depth migration and a post-processing sequence to a seismic reflection line acquired across the Ecuador convergent margin to obtain a 2D-quantitative...
Article
Full-text available
Tectonic processes that control the transition from poorly consolidated sediment entering the subduction channel (SC) to the seismogenic zone are documented using seismic imaging. We applied pre-stack depth migration and a post-processing sequence to a seismic reflection line acquired across the Ecuador convergent margin to obtain a 2D-quantitative...
Chapter
Full-text available
Full waveform inversion is a promising imaging technology for high-resolution images of the subsurface, but suffers from intrinsic non-linearities that require adequate strategies for overcoming them. One crucial issue is related to the starting model from which one has to start when considering local optimization strategies. Depending on the compl...
Conference Paper
Full-text available
Full waveform inversion (FWI) of seismic traces recorded at the free surface allows the reconstruction of the physical parameters structure on the underlying medium. Our two main objectives are the reconstruction of multiple classes of parameters on one side and the formulation of both the acoustic and elastic FWI for 3D geometries. A quasi-Newtoni...
Article
Full-text available
Here we assess the potential of the visco-acoustic frequency domain full-waveform inversion (FWI) to reconstruct P-wave velocity (VP) and P-wave attenuation factor (Q) from surface onshore seismic data. First, we perform a sensitivity analysis of the FWI based upon a grid search analysis of the misfit function and several synthetic FWI examples usi...
Conference Paper
Modelling methods are nowadays at the heart of any geophysical interpretation approach. These are heavily relied upon by imaging techniques in elastodynamics and electromagnetism, where they are crucial for the extraction of subsurface characteristics from ever larger and denser datasets. While high-frequency or one-way approximations are very powe...
Conference Paper
Here we assess the potential of the visco-acoustic frequency domain full-waveform inversion (FWI) to reconstruct P-wave velocity and P-wave attenuation factor (Qp) from onshore seismic data. We show that both the velocity and the attenuation factor can be reliably reconstructed with a comparable resolution and without trade-off for sufficiently att...
Article
Off northwest Libya the Cyrenaica foreland basin domain and its Pan-African continental crust, which constitute the African promontory, are overthrusted by the Mediterranean Ridge Complex. The thrust belt contact and its seismic stratigraphy have been analysed using pre-stack depth-migrated multichannel seismic (MCS) lines recorded during the MEDIS...
Article
Full-text available
A seismic processing workflow based on iterative ray + Born migration/inversion and target-oriented postprocessing of the migrated image is developed for fine-scale quantitative characterization of reflectors. The first step of the workflow involves linear iterations of the ray + Born migration/inversion. The output of the first step is a true-ampl...
Chapter
Full waveform inversion (FWI) is a seismic imaging method suitable for wide aperture / azimuth acquisitions thanks to its ability to account for waves propagating over a broad range of incidence angles. Wide aperture / azimuth acquisitions makes, however, the imaging quite sensitive to anisotropy because of the intrinsic difference between vertical...
Chapter
Full-text available
Anisotropy can have a significant footprint in seismic imaging from surface wide-aperture data, because of the difference between vertical and horizontal velocities in vertical transversely isotropic (VTI) media. A key issue in anisotropic full waveform inversion (FWI) is to define a suitable parametrization of the subsurface model, and the number...
Article
With the tremendous increase of the computational power provided by large-scale distributed-memory platforms and the development of dense 3D multi-component wide-aperture/wide-azimuth surveys, full waveform inversion (FWI) introduced in geophysics by Albert Tarantola has become a re-emerging technique to build high-resolution velocity models of the...
Article
Regional multichannel seismic reflection (MCS) profiles across the Egyptian continental slope, offshore the Nile delta, were recorded during the MEDISIS survey (conducted in 2002 on board the R/V Nadir). The results of this survey allow an interpretation of the overall structure and evolution of this passive continental margin. The MCS data were pr...
Conference Paper
Full-text available
We present an overview of the SEISCOPE project on frequency-domain full waveform inversion (FWI). The two main objectives are the reconstruction of multiple classes of parameters and the 3D acoustic and elastic FWI. The optimization relies on a preconditioned L-BFGS algorithm which provided scaled gradients of the misfit function for each classes o...
Conference Paper
East of the North Island of New Zealand, the Pacific plate subducts beneath the Australian plate along the Hikurangi active margin. There, the continental slope was repeatedly affected by mass-transport processes facilitated by high seismicity, tectonic deformation and high sedimentation rates resulting from the erosion of rapidly-uplifting ranges...
Conference Paper
Full-text available
The North Ecuador - South Colombia convergent margin shows along strike variations in tectonic, thermal and seismogenic features that offer a great opportunity to study the relation between subduction zone tectono-structure, thermal regime and location of the thermally-defined seismogenic zone. Multichannel seismic reflections and conventional bath...