A STRONG quake struck the northern province of Cagayan Tuesday but no damages were reported.

The center of the tectonic quake was located 130 kilometers north-northeast of Tuguegarao City, with a depth of 21 kilometers. It occurred at 10:51 a.m., the Philippine Institute of Volcanology and Seismology (Phivolcs) said.

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A separate monitoring from the United States Geological Survey (USGS) puts the quake at magnitude 5.8 with a depth of 29 kilometers.

The quake was felt at Intensity 5 in Sta. Ana and Aparri in Cagayan; Intensity 4 in Vigan, Ilocos Sur; Intensity 3 in Tuguegarao and Penablanca in Cagayan; Pasuquin, Batac and Laoag in Ilocos Norte and Palanan, Isabela; Intensity 2 in Delfin Albano, Isabela and Santa, Ilocos Sur; and Intensity 1 in the Manila Ocean Park in Manila.

"There were no reports of damage. It would not even trigger a tsunami," Phivolcs Director Renato Solidum said in a text message.

Solidum said a tsunami is likely if a quake is at magnitude 6.5 to 7.0.

The quake was the third quake to jolt the country.

A magnitude-5.1 quake rocked parts of Batanes at pre-dawn Sunday. On Monday, a magnitude-5.0 tremor jolted parts of Davao Oriental province.

No damage or aftershock was reported in both tremors.

An earthquake’s magnitude measures the level of seismic energy the tremor releases while intensity describes the observable effects of the earthquake on the ground.

The Philippines sits on the “Pacific Ring of Fire” where continental plates meet, causing frequent seismic and volcanic activity.

About 20 earthquakes hit the country everyday but only a few are felt.

A magnitude 8.8 shook Chile last February 27.

Solidum told Sun.Star that the recent quake is not an after effect of the earthquake that hit Chile last February 27 with 8.8 magnitude.

"No, there's no relation to the 8.8 earthquake in Chile. We are just both part of the Pacific Ring of fire," he said.

The death toll in Chile climbed to more than 700 and officials estimated 500,000 houses were destroyed or damaged.

Philippines, including Australia and other countries in the Pacific region, raised a tsunami alert Saturday morning.

Philvocs issues Alert level 2 warning in provinces in the eastern seaboard of the country but no drastic effect was felt in the rest of the region.

Arroyo in Tuguegarao

President Gloria Macapagal-Arroyo, who was addressing a crowd of students and farmers in Tuguegarao, remained calm when the earthquake struck.

“Oops there's an earthquake,” Arroyo said in the middle of her speech about the irrigation projects in Cagayan Valley during her address at the F.L. Vargas College in Tuguegarao City.

Arroyo, who was standing in the stage, just stopped and gripped the podium and after five seconds remarked a long “wow” as the crowd awaited the shaking to stop.

None of her security aides or those on the stage rushed to Arroyo who continued her speech 15 seconds later or after the shaking stopped.

“Let’s pray it's not anything like Chile or Haiti,” she said before continuing her speech, referring to the killer quakes in Haiti last month and in Chile last week.

The President after the event, visited Albano in Isabela where she had a luncheon meeting with the members of the El Nino task Force, local government officials of Isabela and Quirino, and inspected the Delfin Albano Irrigation Project.

Mayon alert level lowered

In another development, state volcanologists have lowered the alert level over Mayon volcano from Alert Level 2 to Alert Level 1.

Alert Level 2 was hoisted last January 13, which means a hazardous eruption is less likely although the volcano is showing signs of moderate unrest. Alert Level 1 means no hazardous eruption is imminent.

Tuesday’s bulletin by Phivolcs showed four volcanic earthquakes per day, just around the normal five volcanic earthquakes for Mayon while earthquakes associated with the rising of magma have become rare.

Crater glow has not intensified and steam emissions have been weak, the agency added.

“The above observations suggest that Mayon Volcano’s condition is improving and likely heading towards normalcy,” the Phivolcs said.

The agency, meanwhile, reiterated its warning to residents and tourists not to get near the volcano’s six-kilometer radius Permanent Danger Zone (PDZ) “due to the continuing threat from sudden small explosions and rock falls from the upper and middle slopes of the volcano.”

Last January 1, Phivolcs lowered Mayon Volcano's warning level to Alert Level 3, prompting the Albay government to send majority of the evacuees home because an eruption is less imminent.

Phivolcs said that from December 28, a declining trend in the volcano’s activity was noted.

Prior to that, more than 47,000 people were evacuated from danger zones since the Phivolcs raised Alert level 3 last December 14 and Alert level 4 in December 20 due to the volcano’s restive activity.

Mayon, located about 330 kilometers southeast of Manila, has erupted 48 times in recorded history.

In 1814, more than 1,200 people were killed when lava flows buried the town of Cagsawa. An eruption in 1993 killed 77 farmers. (Virgil Lopez/Glaiza Jarloc/JMR/Sunnex)