Bjørn Ursin became a VISTA Professor in 2008

BJØRN URSIN: VISTA report 2010

VISTA Professor Bjørn Ursin. Photo: Trine Gerlyng

Research: I was visiting professor at the Universidad Federal da Bahia in Salvador, Brazil in January to March and also in December 2010. In November 2010 I was visiting scientist at the Laboratoire de Mecanique et Acoustiqui (LMA), a CNRS laboratory in Marseille, France. The research has been focused on seismic and EM methods. Last years activity has been continued with new results in flux-normalized wave-field decomposition and migration of seismic data. Joint inversion of mCSEM and MT data has successfully been carried out on synthetic data and data from the North Cape Basin. New research activity includes a joint research project with Einar Iversen, NORSAR, Martin Tygel, Unicamp, and Martijn de Hoop, Purdue University on seismic time migration. The first results have been submitted for publication, and more papers are in the pipeline.

Furthermore, a new project is in progress at LMA, Marseille. We have designed a seismic model in PVC which will be used in a water-tank experiment to collect high-frequency (0.5 and 1.0 MHz) seismic data. This data will be used to bench-mark computer programs for seismic modeling. This is a collaboration with researchers at LMA, Marseille, University of Toulouse, NORSAR and Novosibirsk. A new PhD student, Anastasiya Tantsereva, is also working on the project. There is also a new collaboration with Morten Jakobsen at the University of Bergen on inverse scattering methods for seismic and EM data. I am also on the organizing committee of a workshop on Geophysical Imaging with Localized Waves to be held in Sanya, Hainan, China in July 2011.

Honor
Honorary member of the Society of Exploration Geophysicists, 2010

BJØRN URSIN: VISTA report 2008-2009

Research: The research has mainly been focused on seismic methods, and with one PhD student working on marine controlled source electro-magnetic (mCSEM) modeling and inversion.

A new 3D Kirchhoff based approach to seismic modeling has been developed from the tip-wave superposition method. Effective transmission and reflection coefficients for curved interfaces in isotropic or transversely isotropic media provide accurate modeling results including diffractions and head waves.

Improved seismic data processing methods have been developed for non-hyperbolic velocity analysis, geometrical spreading correction for long-offset seismic data and a fast and stable parabolic Radon transform for multiple attenuation and data interpolation. These methods have been applied to data from the Gulf of Mexico.

Seismic migration and imaging has been a main activity. New results have been published on imaging of doubly reflected waves reflected off steeply dipping formations like salt flanks, a stabilized least-squares imaging condition, adaptive focusing windows for seismic angle migration, and methods for wide-angle, one-way wave-equation propagation and imaging of non-converted and converted waves in transversely isotropic media. These methods are useful for imaging with dual-sensor streamer data and data recorded at the seafloor. 2D and 3D versions of the new algorithm have been applied to data from the North Sea. A new approach to seismic imaging using curvelets is being developed in cooperation with professor M. V. de Hoop at Purdue University.

Stereotomography is a slope tomographic method which gives good results for background velocity model estimation in isotropic media. We have developed an extension to 3D anisotropic media for PP and PS reflections, but without taking into account the issue of shear wave degeneracy. Testing on field data is in progress.

We have developed a stochastic simulation approach to the estimation of PP and PS reflection coefficients and elastic parameters from seismic amplitudes. Application has been to data from the Sleipner field. An alternative approach which we have considered is non-linear amplitude-versus-angle inversion and depth imaging in stratified media.

Marine mCSEM data have been modeled and inverted with a contrast source formulation of Maxwell´s equations assuming a transversely isotropic medium. Results with data from the Troll fields indicate that a transversely isotropic medium formulation gives better results than assuming an isotropic medium.

Honors

Biography included in Marquis Who's Who in the World, 1989-90, 1991-92, 1993-94, 2009.