A magnitude-6.0 quake rocked extreme northern Luzon before noon Thursday and was felt as far as the Ilocos region, state seismologists said.
The Philippine Institute of Volcanology and Seismology said the quake was recorded at 10:56 a.m., and was tectonic in origin.
In its bulletin, Phivolcs traced the epicenter to 23 km northwest of Calayan Island.
Phivolcs said the quake was felt at Intensity II in Pasuquin town and Laoag City in Ilocos Norte.
However, it said no damage or aftershock was expected.
The United States Geological Survey measured the quake at magnitude 5.4.
In its bulletin, the USGS said the epicenter was at:
116 km north-northeast of Laoag
168 km south-southwest of Basco, Batanes
233 km north-northwest of Ilagan, Isabela
500 km north of Manila.