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Crustal Rheological Layering Revealed in Multiscale Signals of Natural and Anthropogenic Processes at Pawnee, Oklahoma

Description: 

Oklahoma has experienced a significant increase and decrease in human-induced earthquakes in the past decade. The Mw5.8 Pawnee earthquake in 2016 is the largest recorded event linked to wastewater injection, rupturing a previously unmapped Sooner Lake Fault (SLF). Two months after the event, eight continuous Global Navigation Satellite Systems (GNSS) stations were deployed around the SLF, adding to the growing monitoring networks in the state. Here, we use multi-year geophysical observations from the Pawnee region to estimate the spatiotemporal evolution of seismicity and strain and probe the rheological properties of intraplate faults and crustal layers. We process the GNSS position time series to reveal transient signals due to crustal processes from late 2016 to 2022. The largest rapid deformation signals coincide with an M3.9 event within earthquake swarms in 2019. Interestingly, the GNSS stations farthest from the faults primarily exhibit subsidence, attributable to poroelastic deformation due to changes in injection activities into shallower rock formations. In contrast, near-fault stations show larger horizontal movements and uplift, suggesting an origin of faulting processes. Over the recorded post-seismic period, seasonal signals predominate the vertical GNSS components, whereas the horizontal components show similar steady trends, with intrastation differences in average rates below ~1 mm/yr. The lack of spatially localized, transient geodetic strain suggests that postseismic fault slip is either persistently weak over years or short-lived within two months of the Pawnee event. We further estimate decadal GNSS secular rates over a larger region and find differential movements of ~1 mm/yr between the Pawnee array and nearby stations, which may be explained by the viscoelastic flow of the lower crust. We derive updated source models of the Pawnee mainshock and swarm events to estimate stress changes and assess the contributions of aseismic slip and poroelastic and viscoelastic deformation.

Session: Induced Earthquakes: Source Characteristics, Mechanisms, Stress Field Modeling and Hazards [Poster Session]

Type: Poster

Date: 5/1/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Junle

Student Presenter: No

Invited Presentation: 

Authors