Here we present a super-slow aseismic event model prior to the magnitude 8.3 Kurile Island (Hokkaido-Toho-Oki) earthquake on 4 October 1994 based on data recorded by two tide gauges, located 50--150 km from the earthquake epicenter. Both instruments recorded several cm of subsidence during a five-year period prior to the earthquake. The observed signals are consistent with a precursory quasi-stable slip on the western half of the Hokkaido-Toho-Oki fault plane. When recognized, such aseismic events can considerably improve our intermediate-term (several years) prediction capability.