Fluid-Induced Aseismic Slip: Far-Field Triggering and Static Stress Transfer in the Haynesville Shale Gas Field

Large fluid volume injections into the subsurface are increasingly common across a range of industrial and remediation activities. However, deep fluid injections are often associated with increased seismicity within a few hundred kilometers of the injection sites. The role of aseismic slip as an important precursory signal in induced-seismicity has gained importance in the community due to two reasons: (a) the time and length scales of injection-induced earthquakes are inconsistent with realistic diffusivities, and  fluid-transport models do not match observations, and (b) modern theories of fault weakening suggest that at very high fluid pressures, faults can experience aseismic slip for prolonged periods before ultimately transitioning to unstable, seismic failure driven by static stress transfer.

 

Our work investigates far-field microseism triggering in NE Texas and NW Louisiana within the Haynesville shale-gas field that has developed since 2008. It includes  the 2012 Mw 4.8 Timpson, TX earthquake, which has been attributed to wastewater injection. Seismicity from a temporary array and national monitoring show an increase in the number and magnitude of earthquakes in the area, with regular ML3 events near the Texas-Louisiana border. InSAR data indicate uplift around some injection wells. We consider multiple injection wells and compute the spatial distribution of geodetic strain rates derived from GNSS velocities and compare them with seismic strain rates from new earthquake data. In the decade following the 2012 event, several microseisms across the Texas-Louisiana border have been recorded, suggesting that critically stressed faults in the vicinity are being triggered in part by static stress transfer, as well as newer injection wells.  We compare fault orientations to current stress, consider Coulomb stress change from the Timpson event, and use fluid transport models to explain the seismicity and vertical land motion observed in the Haynesville Shale play area.