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Parametric Estimation of the Local Stress Field in Southern Kansas

Kayla A. Kroll, Keith B. Richards-Dinger, Josha White, & James H. Dieterich

Published August 12, 2019, SCEC Contribution #9452, 2019 SCEC Annual Meeting Poster #284

Accurate determination of state of stress at a field site is key in order to evaluate the geomechanical impacts of any industrial operation that involves injection of fluids into the deep subsurface. Direct borehole measurements of the orientation of the stress field are typically expensive, spatially limited, restricted to shallow depths, and potentially compromised by the drilling itself. Indirect measurements of the stress field orientation with seismic interferometry or through analysis of earthquake focal mechanisms address some limitations of borehole-based approaches, but they require advanced processing techniques and are time consuming. Because earthquakes respond to local properties of the stress field the spatial heterogeneity at the field and fault scale may be inferred based on signatures embedded within a sequence of micro-earthquakes. To decode these signatures we employ the 3D, physics-based earthquake simulation code, RSQSim, to compute several thousand synthetic catalogs of earthquake induced by fluids injected into the subsurface under a variety of stress states. Stresses in the model are represented by different realizations of a stochastic von Karman distribution and tessellated onto a fractally segmented fault surface. Synthetic seismicity catalogs are compared to catalogs of observed induced earthquakes in southern Kansas (Cochran et al., 2018) in order to inter the spatial distribution of the stress field on individual faults. We also conduct a global sensitivity analysis to rank the importance of specific properties of the synthetic catalogs (e.g. total number of events, maximum event magnitude, Gutenberg-Richter statistics, stress drop, etc.) to the key parameters controlling the stress distribution. Results of this analysis may significantly improve understanding of the key physical mechanisms that give rise to observable seismic signatures.

Key Words
Induced seismicity, stress field, Kansas, RSQSim, earthquake simulation

Kroll, K. A., Richards-Dinger, K. B., White, J., & Dieterich, J. H. (2019, 08). Parametric Estimation of the Local Stress Field in Southern Kansas. Poster Presentation at 2019 SCEC Annual Meeting.

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