Abstract

From 2006 through mid-2018, there have been 125 Mw2.5 recorded earthquakes within the Fort Worth Basin and the Dallas-Fort Worth metropolitan area. There is general scientific consensus that this increase in seismicity has been induced by increases in pore-fluid pressure from wastewater injection and from cross-fault pore-pressure imbalance due to injection and production. Previous fault stress analyses indicate that many of the faults are critically stressed; therefore, careful consideration should be taken when injecting in close proximity to these structures. Understanding the structural characteristics that control geomechanical aspects of these earthquake-prone faults is vital in characterizing this known hazard. To improve understanding of faults in the system, we have developed a characterization 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 northeast–southwest, creating a system of elongate horsts and grabens. Fault architectures range from isolated faults to linked and cross-cutting relay systems with individual segments ranging in length from 0.5 to 80 km. The faults that have hosted earthquakes are generally less than 10 km long, trend toward the northeast, and exhibit more than 50 m of normal displacement. The intensity of faulting decreases to the west away from the Ouachita structural front. Statistical analysis of the fault length, spacing, throw, and linkage tendency enables a more complete characterization of faults in the basin, which can be used to mitigate the seismic hazard. Finally, we find that a significant percentage of the total population of faults may be susceptible to reactivation and seismicity as those that have slipped recently.

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