Fluid flow and seismicity pattern: Evidence from the 1997 Umbria-Marche (central Italy) seismic sequence

We model the spatial and temporal evolution of seismicity during the 1997 Umbria-Marche seismic sequence in terms of subsequent failures promoted by fluid flow. The diffusion process of pore-pressure relaxation is represented as a pressure perturbation generated by coseismic stress changes and propagating through a fluid saturated medium. The values of isotropic diffusivity range between 22 and 90 m²/s. The calculated value of anisotropic diffusivity (D_aniso = 250 m²/s) is largest along the average strike (N140°) direction of activated faults. Our results suggest that the observed spatio-temporal migration of seismicity is consistent with fluid flow.