A moderate 5.7 magnitude quake shook Laoag City at 3:58 a.m. Tuesday, followed by two mild tremors hitting the same Northern Luzon city and Ormoc, the Philippine Institute of Volcanology and Seismology said.
There were no reports of damage or injuries from the quakes.
The 5.7 tremor struck 29 kilometers north of Laoag City at a shallow depth of 40 kilometers.
The tectonic quake was felt at Intensity V in Burgos, Pasuiquin, Laoag, Sarrat and Batac, Ilocos Norte; Intensity IV in Sinait, Sur; Aparri, Buguey and Gonzaga, Cagayan; Lubuagan, Kalinga Apayao; Intensity III in Callao , Penablanca, Sta. Ana, Tuguegarao, Cagayan and Intensity II in Santa, Vigan, Ilocos Sur; and Baguio City.
Less than an hour after at 4:44 a.m., a 3.8 magnitude earthquake hit 16 kilometers east of Ormoc City at a shallow depth of five kilometers.
It was followed at a mild 3.2 magnitude tremor that occurred 39 kilometers north of Laoag City. Tectonic in origin, it struck at a shallow depth of 12 kilometers.
The Philippines sits on the Pacific Ring of Fire where continental plates collide causing frequent seismic and volcanic activity.