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Spatiotemporal Evolution of Induced Earthquakes in the Southern Delaware Basin, Reeves-Pecos, West Texas

Description: 

Accurate source characteristics are crucial for assessing the evolution of induced seismicity associated with oil and gas operations and subsurface stress changes in space and time. This study examines the spatial and temporal patterns of seismogenic rupture on critically stressed faults in the Southern Delaware Basin (SDB), west Texas (Reeves and Pecos counties). Utilizing the Hypocentroidal Decomposition method (HD) (www.seismo.com/mloc), we conducted two nested inversions. First, we established a virtual point in space and time, known as Hypocentroid, using a core cluster of local events. We then determined the relative location of all events with respect to this Hypocentroid. The HD relocation improves relative spatial resolution by incorporating data calibration and weighting and mitigates the influence of the 1-D velocity model on earthquake location. We relocated over 6000 events post-2017 provided from the Texas Seismological Network (TexNet) catalog and 73 events from the TXAR catalog (2009-2017) (Frohlich et al., 2020). We supplemented the TXAR and TexNet catalogs by incorporating regional differential times from waveform cross-correlation and local single-station S-P differential times at hypocentral distances less than 10 km, respectively.

After relocation, the mean seismogenic depth of 1.5 km below sea level aligns with the depth of the shallow injection unit, the Bone Spring formation, and is consistent with smaller-scale studies in the region. The spatial correlation between pre- and post-2017 seismicity, along with temporal patterns, maps the expansion of active lineaments in length and number, particularly to the southeast of the study region, as injection activities have evolved. While deeper seismicity is notably absent, this study cannot rule out the involvement of basement faults due to temporal variability in data availability and reduced spatial resolution for deeper seismicity. Our results confirm a prominent influence of pressurization from shallow wastewater injection zones on shallow NW-trending strata-bound faults and the temporal migration of earthquakes along adjacent rupture zones.

Session: Induced Earthquakes: Source Characteristics, Mechanisms, Stress Field Modeling and Hazards - II

Type: Oral

Date: 5/1/2024

Presentation Time: 10:30 AM (local time)

Presenting Author: Asiye

Student Presenter: No

Invited Presentation: 

Authors