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Geologic influence on induced seismicity: Constraints from potential field data in Oklahoma

Recent Oklahoma seismicity shows a regional correlation with increased wastewater injection activity, but local variations suggest that some areas are more likely to exhibit induced seismicity than others. We combine geophysical and drill hole data to map subsurface geologic features in the crystall...

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Published in:Geophysical research letters 2017-01, Vol.44 (1), p.152-161
Main Authors: Shah, Anjana K., Keller, G. Randy
Format: Article
Language:English
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Summary:Recent Oklahoma seismicity shows a regional correlation with increased wastewater injection activity, but local variations suggest that some areas are more likely to exhibit induced seismicity than others. We combine geophysical and drill hole data to map subsurface geologic features in the crystalline basement, where most earthquakes are occurring, and examine probable contributing factors. We find that most earthquakes are located where the crystalline basement is likely composed of fractured intrusive or metamorphic rock. Areas with extrusive rock or thick (>4 km) sedimentary cover exhibit little seismicity, even in high injection rate areas, similar to deep sedimentary basins in Michigan and western North Dakota. These differences in seismicity may be due to variations in permeability structure: within intrusive rocks, fluids can become narrowly focused in fractures and faults, causing an increase in local pore fluid pressure, whereas more distributed pore space in sedimentary and extrusive rocks may relax pore fluid pressure. Key Points Gravity, magnetic, and drill hole data are combined to interpret geologic variations in the crystalline basement of Oklahoma Recent seismicity occurs mostly in areas with fractured intrusive or metamorphic rock, rarely within sedimentary or extrusive rock Focusing of fluids within fractures and faults of crystalline rocks is hypothesized to increase fluid pressure and thus seismicity
ISSN:0094-8276
1944-8007
DOI:10.1002/2016GL071808