Crustal stresses and damage evolve throughout the seismic cycle of the Ridgecrest fault zone
Earthquakes release tectonic stress abruptly, but this stress builds slowly with time through the coupled evolution of faults and the surrounding crust. Seismic wavespeeds track crustal processes, including deformation and stress changes, but typical wavespeed monitoring methods are limited to shallow depths. Using receiver functions, we track wavespeed and anisotropy changes throughout the crust during the 2019 Ridgecrest earthquake sequence. Shallow co-seismic wavespeed reductions throughout the rupture zone recover within months, whereas a deeper wavespeed drop accumulates post-seismically and persists without measurable recovery over several years. This contrasting behavior indicates the mode of deformation changes with depth within the Ridgecrest fault zone. The deep, persistent drop in wavespeed likely reflects accumulating damage driven by post-seismic deformation, suggesting two possible scenarios: (1)~a very slow inter-seismic recovery process, implying wavespeed and anisotropy track long-term stress evolution, or (2)~permanent unrecoverable deformation of an immature fault zone. Both scenarios impact the dynamics and energy budget of the seismic cycle.
