Paper recently accepted at Geochemistry, Geophysics, and Geosystems
The detection and classification of earthquakes in regions previously considered aseismic has led to significant advances in our understanding of anthropogenically induced earthquakes in productive basins. The Eagle Ford of southeastern Texas is one such basin that has seen an increase in earthquakes and a recent TexNet temporary network was deployed in this region to better detect and locate earthquakes. Here we present new results from a joint inversion of ambient noise derived group and phase velocity maps with P to S receiver functions for shear velocity. The first order features of this model include a clear velocity contrast parallel to the Ouachita Marathon Front and thickening of the low velocity upper crust from the northwest towards the Gulf Coast. Secondary features include NE-SW striking variations in the mid-to-upper crust, related to isolated uplifts inferred throughout the region, and variations in the presence and thickness of a high velocity lower crust. These features are anti-correlated such that the region of high velocity upper crust has little lower crust high velocity material. The Luling Uplift is identified as one of these features and we suggest the variations in lower crust structure indicate along-strike variations in the processes involved in the formation and subsequent breakup of Pangea. This model suggests the US-Gulf of Mexico margin morphology is shaped by deformation around the edges of strong blocks and that induced seismicity is focused by these structurally competent features.