Postseismic Evolution of Crustal Faults in California and Oklahoma

Junle Jiang

Published September 8, 2024, SCEC Contribution #14007, 2024 SCEC Annual Meeting Poster #064

Crustal strain along major seismogenic faults accumulates over centuries and is primarily released through earthquakes and subsequent rapid postseismic deformation. In the past two decades, California has experienced several earthquakes of M6 and above, including the 2004 M6 Parkfield, 2010 M7.2 El Mayor‐Cucapah, and 2019 M7.1 Ridgecrest events. Conversely, intraplate regions like Oklahoma historically experienced minimal seismicity until wastewater injection induced seismic activity, culminating in the 2016 M5.8 Pawnee earthquake. This study presents a comparative analysis of these significant events to elucidate the relationship between large and small earthquakes, as well as seismic and aseismic faulting. We use GPS position time-series data and high-resolution seismicity catalogs in these regions to characterize the temporal evolution of seismic and aseismic behavior of the associated fault zones. GPS surface deformation measurements constrain the subsurface moment release of faults, while aftershocks illuminate seismogenesis around coseismic ruptured zones. We find similar evolving patterns of seismicity and inferred fault slip in the early postseismic period across broad spatial scales, with lateral and depth-dependent variabilities. Preliminary integration of GPS and InSAR displacement time-series data for some cases further enhances source resolutions. We compare these selected cases against global-scale compilations of finite-fault earthquake and afterslip models. Notably, the Parkfield and Pawnee cases represent end-member scenarios in terms of the ratio between postseismic and coseismic moment release. The individual case studies and integrated analysis help characterize the transient rheology of crustal faulting while shedding light on the conditions governing aftershock nucleation.

Key Words
Fault zone; afterslip; aftershock; geodesy; source inversion

Citation
Jiang, J. (2024, 09). Postseismic Evolution of Crustal Faults in California and Oklahoma. Poster Presentation at 2024 SCEC Annual Meeting.

Related Projects & Working Groups
Stress and Deformation Over Time (SDOT)