A Decade of Induced Slip on the Causative Fault of the 2015M_w4.0 Venus Earthquake, Northeast Johnson County, Texas

Abstract

On 7 May 2015, a Mw 4.0 earthquake occurred near Venus, northeast Johnson County, Texas, in an area of the Bend Arch‐Fort Worth Basin that reports long‐term, high‐volume wastewater disposal and that has hosted felt earthquakes since 2009. In the weeks following the Mw 4.0 earthquake, we deployed a local seismic network and purchased nearby active‐source seismic reflection data to capture additional events, characterize the causative fault, and explore potential links between ongoing industry activity and seismicity. Hypocenter relocations of the resulting local earthquake catalog span ~4–6 km depth and indicate a fault striking ~230°, dipping to the west, consistent with a nodal plane of the Mw 4.0 regional moment tensor. Fault plane solutions indicate normal faulting, with B axes striking parallel to maximum horizontal compressive stress. Seismic reflection data image the reactivated basement fault penetrating the Ordovician disposal layer and Mississippian production layer, but not displacing post‐Lower Pennsylvanian units. Template matching at regional seismic stations indicates that low‐magnitude earthquakes with similar waveforms began in April 2008, with increasing magnitude over time. Pressure data from five saltwater disposal wells within 5 km of the active fault indicate a disposal formation that is 0.9–4.8 MPa above hydrostatic. We suggest that the injection of 28,000,000 m3 of wastewater between 2006 and 2015 at these wells led to an increase in subsurface pore fluid pressure that contributed to inducing this long‐lived earthquake sequence. The 2015 Mw 4.0 event represents the largest event in the continuing evolution of slip on the causative fault.

Aeromagnetic Data Reveal Potential Seismogenic Basement Faults in the Induced Seismicity Setting of Oklahoma

“…A similar lack of fault offset in sedimentary cover was observed near an induced earthquake swarm in northeastern Texas Scales et al, 2017). The correspondence between earthquake sequences and magnetic gradient peaks or offsets between other linear features in the magnetic anomaly maps suggests that most of the induced earthquakes in Oklahoma involve the reactivation of ancient basement faults.…”

“…Light gray lines show county boundaries; inset shows location of map relative to Oklahoma. For example, in northeastern Texas Magnani et al (2017) and Scales et al (2017) observed only very limited deformation in sedimentary cover associated with a fault that recently experienced induced earthquakes. The basement faults are better aligned with earthquakes than those in the sedimentary cover.…”

The Dallas‐Fort Worth Airport Earthquake Sequence: Seismicity Beyond Injection Period

“…The model consists of a more permeable (5 × 10 À14 m 2 ) Ellenburger formation, where injection occurs, situated between two comparatively less permeable formations-the Barnett shale (1 × 10 À18 m 2 ) above and granitic basement below (1 × 10 À19 m 2 ) (Hornbach et al, 2015;Loucks et al, 2009). The fault width is approximated to 10 m based on the approximate displacement in the regional faults that is in tens of meters Scales et al, 2017). The fault width is approximated to 10 m based on the approximate displacement in the regional faults that is in tens of meters Scales et al, 2017).…”

“…Janská and Eisner (2012)used these data to document a cluster of earthquakes about 4 km north of the S-well beginning in May 2010 through January 2012 (hypocenters approximated by green asterisks, Figure 1). Deployment of local seismic stations in the area by SMU, including redeployment of AFDAD in 2014, revealed small-magnitude earthquakes continued at the airport; earthquakes from 2013 to present are reported in the SMU local earthquake catalog (blue asterisks, Figure 1) (Hornbach et al, 2015;Magnani et al, 2017;Scales et al, 2017).…”

Fluid Injection and Time‐Dependent Seismic Hazard in the Barnett Shale, Texas

“…The overall stress state in the Barnett Shale is consistent with normal faulting regime (Snee & Zoback, 2016) where high-dip-angle faults are oriented along the northeast (Figure 1). The optimal receiver fault geometry used for calculating CFS change is summarized in Table S1 Scales et al, 2017;Snee & Zoback, 2016). The focal mechanism of the DFW Airport sequence is not determined but is perceived to be similar to that of the Cleburne and Azle sequences (Frohlich et al, 2011).…”