HR: 16:45h
AN: G44A-04    [Abstracts]
TI: 3D Joint Inversion of Travel-Time and Potential Field Data Across the Chicxulub Impact Crater
AU: * Vermeesch, P M
EM: peggy.vermeesch@imperial.ac.uk
AF: Department of Earth Science and Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ United Kingdom
AU: Stekl, I
EM: i.stekl@imperial.ac.uk
AF: Department of Earth Science and Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ United Kingdom
AU: Morgan, J V
EM: j.v.morgan@imperial.ac.uk
AF: Department of Earth Science and Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ United Kingdom
AB: The Chicxulub impact crater lies partly offshore/onshore and is buried beneath the Yucatan Peninsula in Mexico. At 180-200 km in diameter, Chicxulub is one of the three largest known impact craters on Earth, and has been associated with the K-T mass extinction. Chicxulub has been the target of several large-scale geophysical experiments and we now have seismic reflection, seismic refraction, gravity, magnetic and magnetotelluric data across this crater. Several distinct structural and lithological models of Chicxulub have been proposed, and they have been constructed using the geophysical data, a limited amount of borehole data, and observations from other terrestrial craters. Deep crustal rocks have been uplifted to within a few kilometers of the Earth's surface near the crater center, but the precise shape and amount of uplift remains unclear. Mapping this uplift is of importance because it will help us to better understand the kinematics and dynamics of crater formation. In an effort to constrain the shape of this stratigraphic uplift, we are in the process of jointly inverting the 3D tomographic travel-time and potential field data. An initial 3D velocity model has been constructed using the travel-time data and the 3D fast code of Zelt and Barton (1998). Velocity is defined along a regular grid. Velocity models are converted to density models (and vice versa) using a relationship determined from measurements on core taken from a borehole in the central crater basin. We intend to use a joint constrained seismic/gravity 3D velocity inversion in the area of dual coverage and gravity only inversion in the rest of the model. Constraints will include velocity/density bounds and smoothing constraints so that the result fits well with the lab density/velocity measurements and to account for different data resolutions of seismic and gravity data. We will explore a number of inversion approaches, and a range of model parameterizations. Once we are satisfied with our procedure we will attempt to incorporate the magnetic field data into the inversion. Zelt, C. A. and P. J. Barton (1998). Three-dimensional seismic refraction tomography: A comparison of two methods applied to data from the Faroe Basin. Journal of Geophysical Research 103: 7187-7210.
DE: 1219 Local gravity anomalies and crustal structure
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting