A Decade of Induced Slip on the Causative Fault of the 2015 M-w 4.0 Venus Earthquake, Northeast Johnson County, Texas

摘要

On 7 May 2015, a M-w 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 M-w 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 similar to 4-6km depth and indicate a fault striking similar to 230 degrees, dipping to the west, consistent with a nodal plane of the M-w 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 5km of the active fault indicate a disposal formation that is 0.9-4.8MPa above hydrostatic. We suggest that the injection of 28,000,000m(3) 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 M-w 4.0 event represents the largest event in the continuing evolution of slip on the causative fault.