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Geomechanical Sensitivities of Injection‐Induced Earthquakes
Author(s) -
Levandowski Will,
Weingarten Matthew,
Walsh Rall
Publication year - 2018
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2018gl077551
Subject(s) - induced seismicity , geology , pore water pressure , seismology , hydrostatic equilibrium , slip (aerodynamics) , overburden , fluid pressure , hydrostatic pressure , geotechnical engineering , mechanics , physics , quantum mechanics , thermodynamics
Wastewater reinjection increases pore fluid pressure and can make faults frictionally unstable, triggering earthquakes. Little is known, however, about how regional geomechanical properties influence the likelihood that disposal will induce seismicity. We investigate the impact of preinjection conditions on the proportion of possible fault orientations destabilized by a specified pore pressure increase. Stress state is the most important factor, with 7 times as many planes unstable in extension than contraction—indeed, normal or strike‐slip faulting environments characterize most injection‐induced seismicity—and additional fivefold increases in transitional stress states. Geomechanical susceptibility depends inversely on overburden density and depth, consistent with the shallow hypocenters of most induced events. The coefficient of friction and initial pore pressure have little impact: Faults initially below hydrostatic pressure can slip during gravity‐fed injection. Combining these factors, site‐specific geomechanical analyses could determine 300‐fold variations in the likelihood of induced seismicity before disposal, offering a proactive way to manage hazard.