RT Journal Article
SR Electronic
T1 Shear-wave anisotropy reveals pore fluid pressure–induced seismicity in the U.S. midcontinent
JF Science Advances
JO Sci Adv
FD American Association for the Advancement of Science
SP e1700443
DO 10.1126/sciadv.1700443
VO 3
IS 12
A1 Nolte, Keith A.
A1 Tsoflias, George P.
A1 Bidgoli, Tandis S.
A1 Watney, W. Lynn
YR 2017
UL http://advances.sciencemag.org/content/3/12/e1700443.abstract
AB Seismicity in the U.S. midcontinent has increased by orders of magnitude over the past decade. Spatiotemporal correlations of seismicity to wastewater injection operations have suggested that injection-related pore fluid pressure increases are inducing the earthquakes. We present direct evidence linking earthquake occurrence to pore pressure increase in the U.S. midcontinent through time-lapse shear-wave (S-wave) anisotropy analysis. Since the onset of the observation period in 2010, the orientation of the fast S-wave polarization has flipped from inline with the maximum horizontal stress to inline with the minimum horizontal stress, a change known to be associated with critical pore pressure buildup. The time delay between fast and slow S-wave arrivals exhibits increased variance through time, which is common in critical pore fluid settings. Near-basement borehole fluid pressure measurements indicate pore pressure increase in the region over the earthquake monitoring period.