• GILBERT P. BAYORAN
The 400-kilometer Negros Trench is capable of generating a magnitude 8.2 earthquake, Director Teresito Bacolcol of the Philippine Institute of Volcanology and Seismology (Phivolcs) said on Monday, Oct. 27.
Bacolcol was among the officials attending the three-day Handa Pilipinas sa Bagong Pilipinas Expo 2025 (Visayas Leg) held at the SMX Convention Center Bacolod.
In a press briefing, he said “if there is a magnitude 8.2 event, and if it is shallow, it could generate tsunami, and will affect the western coastlines of Negros and Panay, even Zamboanga and Palawan.”
He enumerated the three signs of impending local tsunami, including strong ground shaking, sudden drop of sea level, and roaring sound from the sea.
The Negros Trench is an oceanic trench located northeast of the Sulu Trench and west of the Negros Island Region in the Visayas.
Last month, a magnitude 6.9 earthquake hit the northern portion of Cebu, which was also felt in Negros Island while Davao Oriental was jolted by a magnitude 7.4 quake.
In the past several years, Bacolcol said the focus is on the “Big One”, being projected to happen in Metro Manila, which is the economic center of the country.
“But there are bigger ones in other parts of the country,” he added.
The West Valley Fault in Luzon runs roughly 100 kilometers through Bulacan, Metro Manila, and Calabarzon, forming one of the country’s most closely monitored fault systems.
Bacolcol mentioned as well the Philippine Trench, which is being projected to generate a magnitude 8.1 earthquake, with one of the six segments located in Eastern Samar, where a tsunami may take place, based on their modeling, with waves nine to 10 meters high.
The four other main earthquake trenches are the Manila Trench, Sulu Trench, Cotabato Trench, and East Luzon Trough.
“All Filipinos should be prepared since it is not only Metro Manila that will have a strong earthquake,” Bacolcol said.
Science and Technology Secretary Renato Solidum clarified that the eruption of Kanlaon and Taal volcanoes and strong earthquakes in Cebu and Davao Oriental have no connection with each other.
While the eruption of Mt. Pinatubo in 1991 was preceded by a strong earthquake, Solidum said it is not the case with Kanlaon and Taal.
He explained that Kanlaon and Taal have already threatened to erupt even before the strong earthquakes in Cebu and Davao Oriental.
Phivolcs records showed the Philippines experiences 30 earthquakes a day, and in most cases not felt by humans, but only recorded by its instruments. | GB
