Depth seismic-migration modeling offshore Tierra del Fuego by means of an iterative-approach with the inherent crustal-velocity profile.

JOSÉ FLORES; ALBERTO COMÍNGUEZ; ALEJANDRO TASSONE; EMANUELE LODOLO; MARCO MENICHETTI

19-20 de noviembre. Santiago. Chile

Simposio; International Geological Congress on the Southern Hemisfere (Geosur 2); 2007

GEOSUR

Depth-migrated modeling and interpretation of a seismic reflection profile is presented in this paper. The seismic profile in this work is part of the TESAC Project (Tectonic Evolution of the South America-Scotia plate boundary during the Cenozoic), which consists of about 1,200 km of multichannel seismic reflection profiles acquired off the Atlantic coast of the Tierra del Fuego Island. The profiles cut across the South America-Scotia plate boundary, a transform margin which traverses in an E-W direction the Island. Data processing and interpretation of one of these seismic reflection profiles are presented in this contribution. A robust post-stack technique involved depth-migration of the seismic section, using an interval-velocity model of the upper Crust adjusted by iterative processing. The iterative process implemented here is paramount to this project. Processing steps are expected to make way for standardized interpretation of parallel seismic profiles acquired over a single campaign. This should allow us to easily recognize fault displacement as a function of time. Implementation and some hypothesis of the W-X algorithm within the iterative process are discussed. The interpretation results in the recognition of 4 main units on the basis of acoustic fabrics and seismic discontinuities. From bottom to top they are: the acoustic basement (Seismic unit 1), which is overlain by a unit (Seismic unit 2) which displays a tabular geometry and some reflector packages of high amplitude; this unit might be related to the volcanic and volcaniclastic sequences of Tobífera/Lemaire Fms. The Seismic Unit 3 displays an irregular shape and internal reflector configurations of moderate amplitude and continuity and low- to moderate frequency; the onshore Yaghán/Beauvoir Fms could be the surface equivalent of this unit. The uppermost seismic unit (4), located between the ocean floor and the 0.5 sec twt, displays a fairly uniform thickness, it is clearly distinguished from the underlying unit by the low frequency of reflectors with low- to moderate amplitude and continuity. Unit 4 may be correlated with the Tertiary sediments of the Magallanes foreland basin which were involved in the fold and thrust belt.