Phivolcs director Renato Solidum Jr. (File photo)

MANILA – Although the two strong earthquakes that hit Davao Oriental this week did not cause a tsunami threat, Philippine Institute of Volcanology and Seismology (Phivolcs) director Renato Solidum Jr. said the public must remain vigilant against strong earthquakes or tsunamis in the area.

The magnitude 6.2 and magnitude 6.1 quakes this week were caused by movement along the Philippine Trench, Solidum told the Philippine News Agency in an interview on Thursday.

"It (magnitude 6.1 quake early Thursday) had the same epicentral area as the (magnitude 6.2) quake last Tuesday. This supports that large earthquakes can occur in the area and the public needs to be prepared," he said.

Thursday's earthquake struck 78 kilometers southeast of the municipality of Manay, while the earthquake's epicenter last Tuesday was 77 km southeast of the same municipality.

Solidum said both earthquakes, although did not generate a strong impact, should serve as a reminder for the public to prepare for a strong earthquake or tsunami.

"A major earthquake or tsunami can be generated along the Philippine Trench," he said.

Thursday’s quake has intensity IV that was felt in Manay, and intensity II in General Santos City and Tampakan, South Cotabato.

Phivolcs also logged instrumental intensity II in Davao City, Bislig City, Kidapawan City, and General Santos City.

Reported intensity is the traditional way of knowing the intensity based on reports of people who felt the earthquake. On the other hand, instrumental intensity is measured using an intensity meter that measures ground acceleration.

Aftershocks are likely, but no damage is expected since Phivolcs' scale indicate that damage starts at intensity VI.

Solidum earlier said the magnitude 6.2 quake last Tuesday was only felt at maximum intensity IV and is not damaging as it was centered 57 kilometers offshore. (PNA)