Systems and methods for improving injectivity of a hydrocarbon reservoir include: identifying a restriction of flow from an injection well into the hydrocarbon reservoir; transmitting a series of acoustic waves from an injection well into a formation that includes the hydrocarbon reservoir, wherein the series of acoustic waves are transmitted continuously for at least one day; transmitting a series of seismic waves from the injection well into the formation after the series of acoustic waves are transmitted into the hydrocarbon reservoir, wherein the series of seismic waves are transmitted continuously for at least one week; and injecting water into the injection well to cause hydrocarbon of the hydrocarbon reservoir to flow from the hydrocarbon reservoir to a production well after the series of acoustic waves are transmitted into the hydrocarbon reservoir.