Structural Inheritance Control of Induced Seismicity in Central-Eastern US

Abstract:

Most of the recent seismicity in Central and Eastern United States (CEUS) is attributed to the reactivation of pre-existing basement faults by wastewater injection. We analyze the patterns of basement fractures and faults in the Mesoproterozoic Granite-Rhyolite Province of U.S. Mid-Continent as a controlling factor of induced seismicity in CEUS. This basement province of ~1 million km² extends from West Texas to Michigan is mostly buried with a few exposed areas.

Here, we integrate tectonic fabric in crystalline basement outcrops (~2,770 km² in southern Oklahoma and SE Missouri), seismicity patterns in CEUS (for the period 1960 - 2020), and published 3-D seismic reflection fault data (~3,350 km² coverage in central and northern Oklahoma). Our analysis covers ~20% (218,960 km²) of the Granite-Rhyolite Province in CEUS. The analysis of basement outcrops and subsurface revealed sub-vertical fault/fractures with prominent trends of NW and NE in the sub-regions of southern Oklahoma (054°±3.7 & 128°±3.6), central Oklahoma (046°±6.6), NE Oklahoma (053°±9.3 & 119°±0.5), and SE Missouri (059°±2.3 & 119°±1.9). In some places, the fracture datasets show minor trends of N-S and E-W. Likewise, in all the areas of widespread seismicity, the earthquake lineaments dominantly trend NW and NE, given by 059°±2.8 & 116°±3.5 in the Oklahoma-Kansas sub-regions, and 042°±13.2 & 141°±14.6 in the Illinois-Indiana-Michigan-Ohio sub-regions.

We found that the prominent trends of the seismically reactivated faults are parallel to the trends of the independently-mapped pre-existing fracture systems in the basement. The inherited fractures are well-oriented for strike-slip reactivation in the current stress fields in Oklahoma (~085° SHmax) and Illinois (~070° SHmax) (Zoback & Zoback, 1991; Qi, 2016; Alt & Zoback, 2016). Further, our experimental testing of the frictional stability of the Oklahoma basement faults indicates that these faults are susceptible to seismic reactivation (see Kolawole et al., in AGU PPEM Session 103623). We suggest that the inherited basement discontinuities defined the structural fabric and mechanical weakness of the Mid-Continent Precambrian basement to be reactivated by regional fluid injection.