By Ma. Cristina Arayata

Phivolcs Director Teresito Bacolcol (File photo)

MANILA – Residents in coastal areas of Southern Mindanao are advised to be always prepared for earthquakes as neighboring Indonesia also has several active trenches, Philippine Institute of Volcanology and Seismology (Phivolcs) Director Teresito Bacolcol said Thursday.

“There are active trenches in Indonesia that may generate tsunamigenic (large magnitude and shallow) earthquakes. The tsunami waves may travel across Celebes Sea and will reach the southern coasts of Mindanao,” Bacolcol told the Philippine News Agency.

A magnitude 5.7 earthquake was recorded 202 km. southeast of Balut Island in Sarangani, Davao Occidental at 1:01 a.m. Thursday. The tectonic quake was 87 km. deep.

Bacolcol said the earthquake was caused by a trench in Indonesia.

Asked why there was no reported intensity despite the magnitude, he said, the epicenter was far and the earthquake was deep.

Phivolcs recorded Instrumental Intensity II in Glan and Malungon, Sarangani; and Instrumental Intensity I in Digos, Davao del Sur; Nabunturan Davao de Oro; Kiamba, Sarangani; and Tampakan and T’Boli, South Cotabato.

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.

Meanwhile, Phivolcs said aftershocks are likely from the magnitude 5.7 earthquake.

Indonesia and the Philippines lie along the Pacific “Ring of Fire” – the seismic faults around the Pacific Ocean where most of the world’s earthquakes and volcanic eruptions occur. (PNA)