Seismicity diagnostic of permeability creation from centimeter to subkilometer scales in crystalline rock during shear stimulation.

Abstract

Permeability evolves dynamically in the crust and mediates important natural and industrial processes in the subsurface. Episodic microearthquakes generate porosity and, thus, permeability by creating or reactivating fractures. We constrain the form of the scaling relationship linking seismic moment ([Formula: see text]) to incremental permeability generation ([Formula: see text]) through a series of laboratory fault reactivation experiments with absolute constraint on seismic moment. We demonstrate [Formula: see text] proportionality at centimeter scale but confirm predictive power-law scaling using a first-order model as [Formula: see text] from centimeter to subkilometer scale. Stress drop, fault roughness, and deformation modulus condition the prefactor [Formula: see text], extending over 10 decades for reasonable natural parameter ranges. However, observed permeabilities are much more tightly constrained, with [Formula: see text] spanning only two orders of magnitude over length scales from centimeter to subkilometer, suggesting interdependencies in the controlling variables and rendering the relation as diagnostic in predicting fluid flow in crustal reservoirs.