MANILA - (4th UPDATE) A magnitude-7.1 earthquake struck 19 kilometers northeast of the city of Mati, Davao Oriental at 1:46 a.m. Thursday, Phivolcs said.

The earthquake was downgraded from an initial measurement of magnitude 7.3.

The undersea quake, which was tectonic in origin, occurred at a depth of 69 kilometers.

The United States Geological Survey also measured the quake at 7.1.

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A "strong" tremor at Intensity V was felt in Mati City and the towns of Governor Generoso, Baganga, and Lupon in Davao Oriental; Tagum City, Panabo City, and the towns of Carmen and Nabunturan in Davao del Norte; and General Santos City and the towns of Alabel and Malungon in Sarangani.

A "moderately strong" shaking at Intensity IV was felt in Davao City and Kiblawan town in Davao del Sur; Koronadal City and the towns of Tampakan, Tupi and Polomolok in South Cotabato; the towns of Glan, Malapatan, and Kiamba in Sarangani; and Monkayo town in Davao de Oro.

A "weak" tremor at Intensity III was felt in Kabacan town, Cotabato and Bayugan town, Agusan del Sur.

A "slightly felt" Intensity II was recorded in Cagayan de Oro City and Maasim town in Sarangani; and Arakan and Banisilan towns in Cotabato.

A "scarcely perceptible" Intensity I was felt in Mambajao town, Camiguin Island.

The following instrumental intensities were repoted:

• Intensity IV - General Santos City; Kiamba, Sarangani
• Intensity III - San Francisco and Hinunangan, Southern Leyte; Abuyog Leyte; Kidapawan City
• Intensity II - Saint Bernard, Southern Leyte; Dulag and Palo, Leyte; Surigao City
• Intensity I - Alangalang and Carigara, Leyte

Aftershocks and damage to infrastructure are expected, according to Phivolcs.

Phivolcs also said there is no tsunami threat to the country resulting from the earthquake.

In a Facebook post, the city government of Mati said it is monitoring coastal barangays for any possible damage to structures or sudden rise in seawater level.

"As of 2:20 a.m., nothing untoward is reported from all 26 barangays. Amping kita pirmi Matinians!" it added.

In Davao City, workers of different business process outsourcing (BPO) went out of their offices due to the earthquake.

According to Jullan Culano, they went out of the building when they felt the strong quake, which lasted for a few minutes.

—With a report from Hernel Tocmo

The archipelago is regularly rocked by quakes due to its location on the Pacific "Ring of Fire", an arc of intense seismic activity that stretches from Japan through Southeast Asia and across the Pacific basin.

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