“…In the past, most noise-based monitoring studies mainly focused on the changes in coseismic velocities (e.g., Chen et al, 2010;Takagi et al, 2012;Wegler et al, 2009;Wegler & Sens-Schönfelder, 2007;Yu & Hung, 2012;Zaccarelli et al, 2011). In recent years, we have seen a rapid increase in studies on the postseismic velocity changes or recovery of seismic velocity as a result of high-quality and long-term seismic observation (e.g., Gassenmeier et al, 2016;Hobiger et al, 2012Hobiger et al, , 2016Liu et al, 2014;Soldati et al, 2015;Taira et al, 2018;Ueno et al, 2012;Wu et al, 2016). Hobiger et al (2016) systematically studied the characteristics of seismic velocity recovery in different frequency bands of different earthquakes and found that the recovery time constant for all earthquakes was 0.55 years, wherein the coseismic velocity reduction is further divided into two sections: one is potential maximal recovery value, and the other is nonrecovery residual value, and the recovery time constant is defined as the time when the coseismic velocity drop recovers to a factor of 1/e of the maximal recovery value using an exponential fitting algorithm.…”