Strong ground motions from large earthquakes are capable of damaging near-surface sediments and promoting notable reductions in their seismic velocity structures. These velocity reductions can be monitored using either body waves or surface waves from repeatable seismic sources, such as repeating earthquakes or ambient seismic noise. Here we compile a decade-long catalog of repeating earthquakes since the 2004 M_w 9.2 Sumatra Earthquake, and monitor the temporal velocity changes from Rayleigh waves (δV_LR) and Love waves (δV_LQ). We observe a δV_LR of –0.16% and δV_LR/δV_LQ ratio of ~6, inconsistent with velocity reductions in isotropic media. To reconcile the observations, we carry out analyses of sensitivity kernels of surface waves in isotropic and vertical transversely isotropic (VTI) media and forward waveform modeling. The modeling reveals that the observed large δV_LR/δV_LQ ratio can be explained by strong db_V (–4%) and weak db_H (–0.615%) reductions and an increase in radial anisotropy in the near surface. These changes are best explained by a 2% increase in crack density of aligned horizontal cracks in overpressured sediments near the compressive subduction zone environment. Temporal variations of δV_LR/δV_LQ ratios after consecutive great earthquakes are consistent with laboratory experiments under cyclic loading.