MANILA -- A magnitude 5.4 quake struck the waters off Ilocos Norte on Monday, and was felt in neighboring areas, said Phivolcs.
The tectonic temblor hit 14 kilometers northwest of Pagudpud town before 11 a.m., said the seismology office.
At a depth of 15 kilometers, the quake was felt at a "strong" Intensity 5 in Pasuquin, Bacarra and Laoag City in Ilocos Norte, as well as Tuguegarao City, said Phivolcs.
This intensity produces shaking "felt throughout building", and causes hanging objects to swing "violently" and vehicles to "rock noticeably", the agency said.
The quake was also felt at a "moderately strong" intensity 4 in Paoay, Ilocos Norte; and a "weak" intensity 3 in Sinait and Santa towns in Ilocos Sur and Sudipen, La Union.
An intensity 2 shaking was also "slightly felt" in the mountain city of Baguio, said Phivolcs.
The quake may spawn aftershocks, but was not expected to cause major damage to property, it added.
The offshore tremor will not cause a tsunami, said Phivolcs research specialist Myla Advincula.
Phivolcs initially reported the quake's magnitude at 5.8, but later downgraded it to 5.4.
The Philippines straddles the Pacific "Ring of Fire," an arc of intense seismic activity that stretches from Japan through Southeast Asia and across the Pacific basin. The archipelago tallies about 20 earthquakes a day, said Phivolcs.
Last April 23, Magnitude 6.1 quake hit Zambales province and was felt in Metro Manila and other areas. It flattened a supermarket in Pampanga province, made buildings sway in the capital and shuttered the Clark airport for 48 hours.
Less than 24 hours later, a Magnitude 6.5 quake rattled Visayas, leaving 5 hurt and damaging some structures in its epicenter in San Julian, Eastern Samar.