MANILA (Updated 11:41 p.m.) -- Four major undersea earthquakes struck the southern Philippines on Saturday, but the temblors were too deep to cause any damage, state volcanologists said.

Renato Solidum, director of Philippine Institute of Volcanology and Seismology (Phivolcs), told Sun.Star that the temblors were too deep to pose any damage.

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“The epicenter of the earthquake was too deep to affect the areas. The origin range from 570 to 638 kilometers below the surface that’s why these were barely felt,” he said.

No tsunami warning was raised as well. “The earthquakes were too deep to displace the ocean floor and produce a tsunami," said Solidum.

The National Disaster Coordinating Council (NDCC) has also not monitored any damage incurred.

“There are no reported damages in the Cotabato City areas,” said NDCC executive officer and concurrent Office of Civil Defense administrator Benito Ramos. The tremor’s epicenter is in the city.

“We have people there (monitoring). It's just a little shake and it did not cause damage. We did not even see cracks (on structures),” added Ramos. “No damages but (we’re) expecting aftershocks.”

Solidum said the first quake occurred around 6:08 a.m. United States Geological Survey (USGS) recorded the quake at magnitude 7.3 with the epicenter traced to 100 kilometers (km) southwest of Cotabato, 120 km south of Pagadian. It has a depth of 607 kilometers.

Phivolcs said intensity 2 was felt in Surigao City; General Santos City; Cotabato City; Butuan City; Cagayan de Oro City; Lingig, Surigao del Sur; and Soccoro, Surigao del Norte.

A second quake followed at 6:51 a.m. with a magnitude of 7.1, depth of 576 km, and epicenter estimated at 97 km southwest of Cotabato City, according to Phivolcs.

The quake, which was recorded by USGS at 7.6 magnitude, shook other areas in the archipelago including the capital, Metro Manila.

Bedoria Abdullah, science research specialist of the Phivolcs, said the quake was felt at intensity 4 in General Santos City; intensity 3 in Davao City and the towns of Sta. Maria, Malita and Padada in Davao del Sur; intensity 2 in Butuan City, Suriago City, Tacloban City, Palo in Leyte, Dipolog City, Matan-ao in Davao del Sur, Cagayan de Oro City, Cebu City, Soccoro in Davao del Norte, Ayala in Makati City, Palanan in Isabela, and Bayawan in Negros Oriental; and intensity 1 in Midsayap in North Cotabato, Calinan in Davao City, and Makato in Aklan.

Based on Phivolcs scale, an intensity 4 quake is considered as moderately strong and felt generally by people indoors and by some people outdoors.

At 7:15 a.m. a third quake, also of the same magnitude, hit the same area, the Phivolcs said.

The institute also recorded a 6.0 magnitude tremor near Sultan Kudarat province at 1:34 p.m. It was centered about 121 kilometers west of Isulan town in Sultan Kudarat at a depth of 592 kilometers.

Intensity 2 was recorded in Malita in Davao del Sur, San Marcelino in Davao del Sur, and General Santos City.

On Wednesday, two separate quakes rattled parts of Luzon and Visayas but weak enough to pose damage to property, state seismologists reported.

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

About 20 earthquakes hit the country every day but only few are felt.

A 7.9-magnitude quake generated tsunami waves in the Moro Gulf in the south in 1976, killing nearly 5,000 people. A major quake that registered a magnitude 7.7 in 1990 killed nearly 2,000 people on the main northern island of Luzon. (Virgil Lopez/VR/Sunnex)