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Characterizing seismogenic fault structures in Oklahoma

Rob Skoumal, & J. Ole Kaven

Published July 25, 2018, SCEC Contribution #8201, 2018 SCEC Annual Meeting Poster #090

Oklahoma is now one of the most seismically active places in the United States as a result of industry activities. A principal challenge in investigating induced seismicity is the identification and characterization of seismogenic faults. Earthquake locations can illuminate dense fault fabrics previously unbeknownst to seismologists and provide insight into the rupture process. In order to characterize these fault networks in Oklahoma, we created a catalog of over 200,000 earthquakes identified using large-scale template matching and relocated the events using GrowClust. To make the process of identifying fault segments more easily accessible and objective, we developed an algorithm that 1) identifies clusters of seismicity and 2) distinguishes linear/planar features within each cluster. With this approach, we are able to rapidly characterize a wide variety of fault features, such as strike, dip, and depth, and also identify conjugate faults within the improved earthquake catalog. We investigate the largest magnitude earthquake sequences in greater detail, including the 2011 M 5.7 Prague and 2016 M 5.8 Pawnee earthquakes, in addition to characterizing numerous faults throughout the state that have not been previously identified. The improved catalog also allows hydraulic fracturing induced seismicity to be characterized with greater confidence, and we find that these earthquakes have strong spatiotemporal correlations with the relatively short-duration hydraulic stimulations. The vast majority of seismogenic faults identified are optimally oriented relative to in-situ maximum principal horizontal stress measurements and are in agreement with moment-tensor solutions, where available. Using the cross-correlation coefficients between event pairs, moment tensors of smaller magnitude events can also be estimated, providing deeper insight into the rupture processes.

Key Words
Induced Seismicity Fault Characterization

Skoumal, R., & Kaven, J. (2018, 07). Characterizing seismogenic fault structures in Oklahoma. Poster Presentation at 2018 SCEC Annual Meeting.

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