Hardest hit was Santa town where the waves brought down a concrete seawall constructed along the shorelines of Barangays Quezon, Magsaysay, Bucalag and Pasungol.
"It looked like it was a tidal wave," said Santa Mayor Jesus Bueno Jr.
A tidal wave struck Santa in l980, killing five villagers and sweeping away houses in four barangays.
The other coastal villages affected were in Vigan City and in the towns of Caoayan, Sta. Catalina, Narvacan, Sta. Maria, San Esteban, Santiago, Candon, Sta. Lucia, and Sta. Cruz.
There were no reports of casualties.
Ilocos Sur Gov. Luis "Chavit" Singson instructed the concerned municipal officials to maintain a 24-hour alert.