Spatiotemporal evolution of the 2011 Prague, Oklahoma, aftershock sequence revealed using subspace detection and relocation

Abstract

The 6 November 2011 Mw 5.7 earthquake near Prague, Oklahoma, is the second largest earthquake ever recorded in the state. A Mw 4.8 foreshock and the Mw 5.7 mainshock triggered a prolific aftershock sequence. Utilizing a subspace detection method, we increase by fivefold the number of precisely located events between 4 November and 5 December 2011. We find that while most aftershock energy is released in the crystalline basement, a significant number of the events occur in the overlying Arbuckle Group, indicating that active Meeker‐Prague faulting extends into the sedimentary zone of wastewater disposal. Although the number of aftershocks in the Arbuckle Group is large, comprising ~40% of the aftershock catalog, the moment contribution of Arbuckle Group earthquakes is much less than 1% of the total aftershock moment budget. Aftershock locations are sparse in patches that experienced large slip during the mainshock.

Narrow Spatial Aftershock Zones for Induced Earthquake Sequences in Oklahoma

“…A by‐product of heightened unconventional oil and gas production in the Central United States over the past decade have been sharply rising and highly variable seismicity rates, mostly linked to the disposal of produced wastewater (Ellsworth, ). Most of the recent seismicity in the broader region has occurred in the state of Oklahoma, which has been characterized by high productivity swarms (Benz et al, ), elevated background rates (Walsh & Zoback, ), and four large mainshocks of M 5 and greater since 2011 (Chen et al, ; Goebel et al, ; McGarr & Barbour, ; McMahon et al, ; Walter et al, ; Yeck et al, ). Although the earthquake rate has been declining since 2016 in Oklahoma due to both market‐driven reductions in new production wells in central Oklahoma and mandated regional wastewater injection rate reductions (Baker, ), it remains well above pre‐2009 levels.…”

Oklahoma's induced seismicity strongly linked to wastewater injection depth

“…Wastewater disposal via deep injection wells explains the surge in earthquake activity (1)(2)(3)(4)(5)(6)(7). In many cases, pressurized fluids migrate from target formations downward into the crystalline basement (1,(7)(8)(9)(10), where most earthquakes occur (11)(12)(13)(14)(15)(16)(17)(18). The disposed fluids may locally increase pore fluid pressure and reduce the effective stress along faults (2,9,11), resulting in induced seismicity (2,19).…”

SBAS Analysis of Induced Ground Surface Deformation from Wastewater Injection in East Central Oklahoma, USA

“…The Meeker-Prague Fault splay is also a conjugate fault. There have been a number of studies that have linked the increased seismicity along the Meeker-Prague Fault to wastewater injection wells [3,58,60]. Calculated Coulomb failure stress changes along the Cushing Fault were compared to data from the November 2011 Prague earthquake along the Meeker-Prague fault [63].…”

“…In November 2011, it was the location of the second strongest recorded earthquake in Oklahoma history [3,58]. Three earthquakes of M w 5.0, 5.7 and 5.0 occurred within 4 days along the strike-slip Meeker-Prague fault, a 20 km splay off the main Wilzetta Fault Zone [60], approximately 4 miles east of the town of Sparks, Oklahoma. The epicenters of these events were located 180 km from the nearest known Quaternary-active faults [3].…”

“…A number of studies [3,58,60] have linked these earthquakes to nearby wastewater injection wells. Work by [3] proposed that this sequence of earthquakes was not only due to wastewater injection, but was the result of over twenty years of wastewater injection in the area, and not an immediate response to wastewater injection initiation or volume change [61].…”