Banca de DEFESA: BRUNO BARAUNA DOS SANTOS

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : BRUNO BARAUNA DOS SANTOS
DATE: 26/11/2021
TIME: 09:30
LOCAL: videoconferência
TITLE:

Incorporating attenuation in time-domain GPR modeling with the Q-constant model and using
multiple Debye poles: Theory and application in fractured and karstified carbonte rocks

KEY WORDS:

Attenuation; Debye model; constant-Q model; Time-domain GPR modeling; Karst.

PAGES: 71
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUMMARY:

Dispersion and absorption are important effects contributing to attenuate real GPR (Ground Penetrating Radar) signals and must be incorporated in wave propagation. The constant-Q model (Quality Factor Q) is valid for most rocks for typical GPR frequency ranges. In time-domain wave modeling, to simulate a constant-Q model, using a superposition of multiple Debye poles, the number of poles and their parameters must be previously specified, given target values for Q and velocity and the useful frequency band of the wavelet. For electromagnetic (and also viscoelastic) waves, this problem is usually formulated as a highly nonlinear optimization problem presenting several solutions, which is solved using global optimization methods. An efficient linear approach to estimate multiple Debye poles to simulate constant-Q models in GPR data is presented. The resulting inverse problem is easy to solve because the number of demanded poles is quite small. For the usual GPR frequency bands, just two or three poles are necessary. The gain in efficiency is particularly high because the approach allows to obtain a rescaled solution that depends just on the frequency band and number of poles. Specific solutions satisfying target values for velocity and Q are obtained from the rescaled solution. Choosing the number of poles is tentatively done so that both velocity and Q curves, as function of frequency, are approximately constant in the specified frequency band. To minimize computational costs in time-domain modeling, as few poles as possible should be used. The importance of introducing attenuation effects is exemplified by presenting a trial-and-error modeling approach to reproduce, as close as possible, a 200 MHz field GPR section acquired in fractured and karstified carbonate rocks.

BANKING MEMBERS:
Externo à Instituição - JESSÉ CARVALHO COSTA - UFPA
Externo à Instituição - PEDRO XAVIER NETO - PETROBRAS
Presidente - 349684 - WALTER EUGENIO DE MEDEIROS