Magnetotelluric inversion constrained by seismic data in the Tucumán Basin (Andean Foothills, 27°S, NW Argentina)

ALICIA FAVETTO; CRISTINA POMPOSIELLO; JOHN BOOKER; EDUARDO ROSSELLO

JOURNAL OF GEOPHYSICAL RESEARCH

American Geophysical Union

Año: 2007 vol. 112 p. 1 - 12

0148-0227

A magnetotelluric (MT) profile and conventional seismic reflection lines are used to characterize the sedimentary basin across the Andean foothills in the Tucumán plain. This basin is a depocenter surrounded by crystalline basement and filled with a several kilometers-thick sedimentary sequence. Due to the high contrast in electrical resistivity between the basin sedimentary rocks and the crystalline basement, this interface dominates the MT response and masks details of the structure within the sedimentary units. This paper presents a new interpretation of the MT data incorporating structure constraints obtained from a network of seismic lines. Our results indicate that a significantly improved characterization of the conductive horizons within the basin is obtained when resistivity model discontinuities are introduced at the seismic reflectors corresponding to the most important formation boundaries.  Improved resistivities of the main formations, Cretaceous-Miocene and Miocene-Pliocene, were inferred. The comparison of constrained and unconstrained models constitutes an instructive case study of how controlled MT inversion can improve structure imaging. It also shows that the application of constraints in the inversion process is a worthy option to find a geologically-supported model, especially if data misfit shows a marked non-random distribution.