How faulting keeps the crust strong

Abstract

Deep drilling and induced seismicity experiments at several locations worldwide indicate that, in general, the brittle crust in intraplate regions is critically stressed, pore pressures are close to hydrostatic, and in situ bulk permeability is ∼10 −17 to 10 −16 m 2 . This high permeability, three or four orders of magnitude higher than that measured on core samples, appears to be maintained by critically stressed faults and greatly facilitates fluid movement through the brittle crust. We demonstrate that such high permeabilities can maintain approximately hydrostatic fluid pressures at depths comparable to the thickness of the seismogenic crust. This leads to the counterintuitive result that faulting keeps intraplate crust inherently strong by preventing pore pressures greater than hydrostatic from persisting at depth.