Deciphering the Stress State of Seismogenic Faults in Oklahoma and Southern Kansas Based on an Improved Stress Map

Journal Article · Sat Nov 23 00:00:00 EST 2019 · Journal of Geophysical Research. Solid Earth

DOI:https://doi.org/10.1029/2019JB018377· OSTI ID:1581273

Qin, Yan  ^[1]; Chen, Xiaowei  ^[1]; Walter, Jacob I.  ^[1]; Haffener, Jackson ^[1]; Trugman, Daniel T.  ^[2]; Carpenter, Brett M.  ^[1]; Weingarten, Matthew  ^[3]; Kolawole, Folarin  ^[1]

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1. Univ. of Oklahoma, Norman, OK (United States)
2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
3. San Diego State Univ., CA (United States)

Fault location and geometry are prime considerations in the reactivation of preexisting faults. Here, we combine relocated earthquake catalogs and focal mechanisms to delineate seismogenic faults in Oklahoma and southern Kansas and analyze their stress state. Initially, we identify and map seismogenic faults based on earthquake clustering. We then obtain an improved stress map using 2,047 high-quality focal mechanisms. The regional stress map shows a gradual transition from oblique normal faulting in western Oklahoma to strike-slip faulting in central and eastern Oklahoma. Stress amplitude ratio shows a strong correlation with pore pressure from hydrogeologic models, suggesting that pore pressure exhibits a measurable influence on stress patterns. Finally, we assess fault stress state via 3-D Mohr circles; a parameter understress is used to quantify the level of fault criticality (with 0 meaning critically stressed faults and 1 meaning faults with no applied shear stress). Our findings suggest that most active faults have near vertical planes (planarity >0.8 and dip >70°), and there is a strong correlation between fault length and maximum magnitude on each fault. The fault trends show prominent conjugate sets that strike [55–75°] and [105–125°]. A comparison with mapped sedimentary faults and basement fractures reveals common tectonic control. Based on 3-D Mohr circles, we find that 78% of the faults are critically stressed (understress ≤0.2), while several seismogenic faults are misoriented with high understress (>0.4). Fault geometry and local stress fields may be used to evaluate potential seismic hazard, as the largest earthquakes tend to occur on long, critically stressed faults.

• Research Organization: Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: 89233218CNA000001
• OSTI ID: 1581273
• Report Number(s): LA-UR-18-27043; TRN: US2100716
• Journal Information: Journal of Geophysical Research. Solid Earth, Vol. 124, Issue 12; ISSN 2169-9313
• Publisher: American Geophysical Union
• Country of Publication: United States
• Language: English