[Alumnos] HOY 14 hs. - Charla SEG

Mar Ago 29 07:33:05 -03 2017

Estimados,

Les recordamos que hoy tendremos la siguiente Charla  de la Sociedad de 
Alumnos de Geofísica de la FCAG-UNLP (SEG) a las 14hs. en el Salón 
Meridiano.

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Secretaría de Ciencia y Técnica
FCAG

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*Charla de la SEG*

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Sociedad de Alumnos de Geofísica de la FCAG-UNLP (SEG Student  Chapter)

La charla está dentro del marco del "Honorary Lecture Program" 
organizado por la Society of Exploration Geophysicists (SEG).

Disertantes: Prof. Martin Tygel (Universidad de Campinas SP, Brasil)

Título: "Multiparametric traveltimes: Concepts and applications".

Resumen: Traveltime stacking is one of the most fundamental tools in the 
processing of multicoverage seismic data. The most popular stacking 
traveltime is the normal moveout (NMO), upon which the celebrated 
common-midpoint (CMP) method is based. Established in the 1960s, the CMP 
method remains as an obligatory step in any seismic processing sequence. 
The NMO stacking traveltime depends on a single parameter (the NMO 
velocity) and is performed on individual CMP gathers, thus depending on 
offset only. In spite of its well-recognized good properties, such as a 
valuable zero-offset (ZO) stacked section and an NMO-velocity field, NMO 
stacking can be seen to have two main drawbacks: The first one is that 
it employs only a fraction (CMP gathers) of the multicoverage data and, 
as a consequence, takes no advantage of the redundancy contained in the 
full data. The second one is the fact that it delivers a single 
parameter (NMO velocity), not much information extraction from the huge 
and costly seismic data.

In the 1980s, in response to the demands of seismic processing in 
anisotropic media, multiparametric nonhyperbolic moveouts came into 
play. Still dependent on offset only, such moveouts mainly were applied 
to transverse anisotropic media with a vertical axis of symmetry. 
Moveout extensions for more complex anisotropic media are available in 
recent literature, being a topic of active ongoing research.

A vigorous attempt to overcome the limitations of offset dependent 
moveouts came about in the late 1990s by the introduction of 
multiparametric moveouts depending on both midpoint and offset 
coordinates and also fully in 3D. Moreover, the parameters introduced in 
the new traveltimes were seen to be very useful for other imaging 
purposes, such as, e.g., time migration, separation of reflections and 
diffractions, time-to-depth conversion, tomography and, more recently, 
data regularization.

In this lecture, I discuss the multiparametric traveltimes that are the 
most natural extensions of the classical single-parameter NMO and 
time-migration moveouts. More specifically, these are the 3D hyperbolic 
(second-order Taylor polynomial) mainly designed for reflections and 
double-square-root (sum of two hyperbolic moveouts), mainly designed for 
diffractions. Both traveltimes are defined for varying midpoint and 
half-offset coordinates.

Besides a brief discussion of the traveltime expressions and 
interpretation of their parameters, various applications on the 
above-mentioned topics are presented. Finally, perspectives and actual 
challenges of the multiparametric traveltime approach to seismic imaging 
are commented.

Biografía:

Martin Tygel received his BSc in physics (1969) at the State University 
of Rio de Janeiro and MSc in mathematics (1973) at the Catholic 
University of Rio de Janeiro. After being awarded by a fellowship of the 
Brazilian Council of Research and Technological Development (CNPq), he 
obtained the MSc (1976) and PhD (1979) in mathematics at Stanford 
University. He has taught at the Federal University of Rio Grande do 
Norte (1979–1981) and the Federal University of Bahia (1981–1983), being 
responsible there for the mathematical disciplines at the joint graduate 
program in geophysics together with Petrobras. In 1984, he joined the 
University of Campinas

(Unicamp), where he is located until today. Prof. Tygel has also been a 
Humboldt scholar (1985–1987) in Hannover (Germany), and also a visiting 
professor at the Universities of Karlsruhe (Germany) (1990) and 
Trondheim (Norway) (2007–2008). In 2002, he received the Conrad 
Schlumberger Award of the European Association of Geophysicists and 
Engineers.  In 1997, Prof. Tygel was one of the founders of the Wave 
Inversion Technology (WIT) Consortium. In 2001, he founded the 
Computation Geophysics Laboratory at the Department of Applied 
Mathematics at Unicamp, and in 2013, he founded the High Performance 
Geophysics (HPG) Lab at the Center of Petroleum

Studies also at Unicamp. The latter has a special emphasis in 
integrating geophysics results with high-performance computing (HPC) so 
as to optimize their most direct practical application. Besides his 
scientific activities which include three books and more than 200 
publications in international journals and proceedings of international 
congresses, Prof. Tygel has a long experience in carrying out projects 
which involves academia and the oil industry. His research interests are 
in methodologies and algorithms of seismic processing, imaging, and 
inversion that have a sound basis on wave propagation and find practical 
application to exploration and monitoring of hydrocarbon reservoirs.

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