--> Characteristics of Potentially Seismogenic Faults in the Greater Fort Worth Basin

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Characteristics of Potentially Seismogenic Faults in the Greater Fort Worth Basin

Abstract

The Fort Worth Basin (FWB) of north-central Texas initiated as a flexural foreland basin in the Late Paleozoic. The basin is of particular interest because from 2006 through mid-2018 there have been 125 Mw ≥ 2.5 earthquakes within it impacting the DFW area. There is general scientific consensus that this increase in seismicity has been induced by increases in pore fluid pressure from waste water injection and from cross-fault pore pressure imbalance due to injection and production. Fault stress analysis shows that a majority of the faults are critically stressed, therefore careful consideration should be taken when injecting in close proximity to these structures. Understanding the structural and geomechanical characteristics of these earthquake-prone faults is of the utmost importance.

To improve the understanding of the basin we provide a characterization of the faults using a new basin-wide fault interpretation and database that has been assembled through the integration of published data, 2D and 3D seismic surveys, outcrop mapping, earthquakes, and interpretations provided by operators resulting in a 3D structural framework of basement-rooting faults. Our results show that a primary fault system trends to the northeast, creating a system of elongate horsts and grabens. Fault architectures range from isolated faults to complexly-linked relay systems with individual segments ranging from 0.5 to 80 km. The faults that have hosted earthquakes are generally less than 10 km long. The intensity of faulting decreases to the west away from the Ouachita structural front which was active during their formation. Statistical analysis of fault length, spacing, throw, and linkage tendency enables a more complete characterization of faults in basin which is used to refine the hazard assessment.