Measuring variations of seismic attenuation over time, while requiring extreme measurement sensitivity, provides unique insights into the dynamic state of stress in the Earth’s crust at depth. We analyze seismic data from earthquakes of the 2016-2017 Central Apennines seismic sequence and obtain high-resolution time histories of seismic attenuation in a wide frequency band (0.5-30 Hz) that are characterized by strong earthquake dilatation-induced fluctuations (deep), as well as damage-induced ones (shallow). The cumulative elastic stress drop after the sequence causes negative dilatation, reduced permeability and seismic attenuation. We observe that M≥3.5 earthquake occurrence vs. time and distance is consistent with fluid diffusion, and that these diffusion signatures are associated with changes in seismic attenuation during the first days of the Amatrice, Visso-Norcia, and Capitignano sub-sequences. We conclude that coseismic permeability changes, partially evidenced by seismic attenuation, create fluid diffusion pathways that are at least partly responsible for triggering multi-mainshock seismic sequences.