Sedimentary and crustal structure of the US Gulf Coastal Plain revealed by Rayleigh wave and receiver function data: Implications for continental rifting

Abstract:

We developed a high resolution 3-D Vs model of the sediment and crust beneath the US Gulf Coastal Plain north thru the Ouachita fold-and-thrust belt, and Mississippi Valley Graben to southern Missouri. We first conducted H-κ analysis of receiver function data to provide an initial crustal thickness model, then we used that to constrain a joint inversion of Rayleigh wave phase velocities and Z/H ratios, and teleseismic P-coda waveforms data. The surface- and body-wave measurements were derived, respectively, from ambient noise and teleseismic earthquakes recorded by 215 USArray stations in a rectangular area from 100°-87° west and 28°-37° north. We used Z/H ratios in the period range of 8-25 s and a cross-convolution misfit function for fitting the P-wave coda in order to better constrain sedimentary structures. We found that the measured phase velocities, Z/H ratios, sediment basement depths, Moho depths, average crustal Vp/Vs ratios, and Vs are all well bounded by the front of the Ouachita fold-and-thrust belt. The 3-D velocity structure suggests that continental rifting between the North America plate and the Yucatan block initiated in a northwest-southeast direction with a rift axis aligned with the southeast Texas coast, along the strike of the large magnitude Houston magnetic anomaly. The observed seismic structures of the crust and uppermost mantle beneath the Mississippi Embayment and the Mississippi Valley Graben are also consistent with a plume origin of the Mississippi Embayment.