Receiver Functions and Surface Wave Dispersion Modeling of the Crust and Upper Mantle beneath the Texas Gulf Coast

Abstract

The Gulf of Mexico is a relatively small oceanic basin that formed as a result of rifting between the continental blocks of North America and the Yucatan in the Middle to Late Jurassic (165 Ma). The extent to which the continental crust was stretched and thinned prior to breakup is currently unknown. The seismic structure beneath the Texas Gulf Coastal Plain is determined by migration of stacked common conversion point (CCP) PS receiver functions and surface wave dispersion. The Gulf Coastal Plain is a portion of an ocean-continental transition zone, or ‘passive margin,’ where seismic imaging of the lithospheric earth structure has been rare.

Seismic data from a temporary array of 22 broadband stations, spaced 16–20 km apart, on a ~380-km-long profile from Matagorda Island, a barrier island in the Gulf of Mexico, to Johnson City, Texas, were employed to construct a coherent image of the crust and uppermost mantle. CCP stacking was applied to the data from teleseismic earthquakes to enhance the signal-to-noise ratios of converted phases, such as PS phases. An inaccurate velocity model, used for time-to-depth conversion in CCP stacking, ma produce higher errors, especially in a region of substantial lateral velocity variations. An accurate velocity model is therefore essential to constructing high quality depth-domain images. To find accurate velocity P- and S-wave models, we applied a global optimization approach that searched for 1D best-fitting shear velocity models via Very Fast Simulated Annealing by modeling dispersion curves. We used ambient noise cross-correlation to compute the Rayleigh wave group velocity dispersion curves.

AAPG Datapages/Search and Discovery Article #90219 © 2015 GCAGS, Houston, Texas, September 20-22, 2015