Communities located along the country’s six major active trenches remain at risk of powerful earthquakes that could reach magnitude 8.2, the Philippine Institute of Volcanology and Seismology (Phivolcs) said Tuesday.
Phivolcs Director Teresito Bacolcol said these seismic zones include the Philippine Trench, stretching from East Luzon to Southeast Mindanao; the East Luzon Trough; the Manila Trench; the Negros Trench; Sulu Trench; and the Cotabato Trench—all of which are capable of generating strong offshore earthquakes.
His statement followed the magnitude 7.8 offshore Sarangani earthquake that struck parts of Mindanao earlier this week, which was traced to movement along the Cotabato Trench. Bacolcol said it was the strongest recorded earthquake in the country so far this year.
He noted, however, that the Philippines’ most powerful recorded earthquake remains the magnitude 8.1 tremor that hit Mindanao in 1976.
Bacolcol clarified that while recent events are linked to specific trench systems, earthquake impacts are not confined to a single point, as fault and trench structures extend over long distances.
He stressed that coastal communities are particularly at risk of tsunami hazards triggered by strong offshore quakes and urged residents to be alert to natural warning signs.
These include intense ground shaking, sudden unusual changes in sea level, and loud roaring sounds from the ocean, which may signal an incoming tsunami.
Authorities continue to remind the public that earthquakes strike without warning, making preparedness and immediate evacuation to higher ground critical for communities in vulnerable coastal areas.
Open-source geological references note that the six trenches rank among the country’s principal active subduction zones.
While Palawan is often considered one of the least earthquake-prone provinces in the Philippines, scientists say a major geological feature beneath nearby waters continues to pose a potential hazard: the Sulu Trench.
Located in the Sulu Sea between Palawan and the Sulu Archipelago, the Sulu Trench is one of the country’s active ocean trenches. It was formed by the movement of tectonic plates beneath the seafloor, creating a deep underwater depression that stretches across parts of the southwestern Philippines.
Geologists classify the Sulu Trench as an active subduction zone, meaning that one section of the Earth’s crust slowly forces itself beneath another. This process can generate earthquakes and, under certain conditions, tsunamis.
Although the trench is generally less active than the Manila Trench west of Luzon or the Philippine Trench east of Mindanao, experts say it remains capable of producing significant seismic events.
The trench’s proximity to Palawan makes it particularly important for coastal communities. Southern Palawan, including municipalities facing the Sulu Sea, is geographically closer to the trench than many other parts of the country. While large earthquakes linked to the Sulu Trench are relatively uncommon, scientists continue to monitor the area as part of the country’s broader earthquake and tsunami risk assessment efforts.
