Attribute-assisted characterization of basement faulting and the associated sedimentary sequence deformation in north-central Oklahoma

Abstract

Patterns of recent seismogenic fault reactivation in the granitic basement of north-central Oklahoma necessitates an understanding of the structural characteristics of the inherited basement-rooted faults. One area is the Nemaha Uplift and Fault Zone (NFZ) in north-central Oklahoma. We have analyzed the top-basement and intrabasement structures in eight poststack time-migrated 3D seismic reflection data sets. Overall, our results reveal 115 fault traces at the top of the Precambrian basement with dominant trends of west-northwest–east-southeast, northeast–southwest, and north–south. We observe that proximal to the NFZ, faults dominantly strike north–south, are fewer (<10), and have the lowest areal density and intensity, while displaying the maximum vertical separation. However, farther away from the NFZ, faults exhibit predominantly northeast–southwest trends, fault areal density and intensity increases, and max. vertical separation decreases steadily. Of the analyzed faults, approximately 49% are limited to the intrabasement, approximately 28% terminate within the Arbuckle Group, and approximately 23% transect units above the formation. These observations suggest that (1) proximal to the NFZ, deformation is dominantly accommodated along a few but longer fault segments, most of the mapped faults cut into the sedimentary rocks, and most of the through-going faults propagate farther up-section above the Arbuckle Group and (2) with distance away from the NFZ, deformation is diffuse and distributed across relatively shorter fault segments and most basement faults do not extend into the sedimentary cover. The existence of through-going faults suggests the potential for spatially pervasive fluid movement along faults. Further, observations reveal pervasive, subhorizontal intrabasement reflectors (igneous sills) that terminate at the basement-sediment interface. Results have direct implications for wastewater injection and seismicity in north-central Oklahoma and southern Kansas. Additionally, they provide insight into the characteristics of basement-rooted structures around the NFZ region and suggest a means by which to characterize basement structures where seismic data are available.

A physics-informed optimization workflow to manage injection while constraining induced seismicity: The Oklahoma case

“…Analogous to the analysis by Zhai et al (2019), vertical strike-slip faults with a unique preferred fault strike azimuth of 50 °are assumed to be ubiquitous in the basement. This faulting regime and the fault orientation is consistent with the statistical analysis of earthquake focal mechanisms, in situ stress analysis, field mapping, and 3D seismic interpretation at Oklahoma (Holland, 2013;Alt and Zoback, 2016;Kolawole et al, 2019;Qin et al, 2019;Firkins et al, 2020). Principal stresses are assumed to be spatially uniform around Oklahoma with a maximum horizontal stress azimuth oriented at 85 °.…”

Teleseismic waves reveal anisotropic poroelastic response of wastewater disposal reservoir

“…Considering the azimuthal, anisotropic response measured in the Arbuckle reservoir, and increasing evidence that basement rooted faults extend into the Arbuckle Group (e.g., Firkins et al, 2020), the primary implication for the triggering mechanisms of the events studied by van der Elst et al (2013) is that a more complex interaction between dynamic stresses, pore pressure changes, and subsurface structure and rock properties is at play. Further, the details of static stress changes affecting earthquake‐to‐earthquake interactions should also consider the potential for coupling between pore pressure and shear deformation (e.g., Wang HF, 1997).…”

Slip Characteristics of Induced Earthquakes: Insights From the 2015 Mw 4.0 Guthrie, Oklahoma Earthquake

“…The possible causes for these reactivated faults exhibiting the behavior commonly attributed to immature faults could be due to several factors, such as: (1) the faults being immature with low net slip history; (2) alteration and healing that has occurred during their dormancy has caused them to exhibit the behavior of immature faults. The length of faults activated in Oklahoma are often <30 km based upon earthquake locations and 3D seismic reflection surveys (Firkins et al, 2020;Kolawole et al, 2019Kolawole et al, , 2020Qin et al, 2019), implying that they have not yet accommodated the level of displacement that one would expect for mature faults (>1000 km) determined in past studies (Manighetti et al, 2007;Perrin et al, 2016). However, 3D seismic reflection surveys measurements of fault length are limited by survey area.…”