Phivolcs warns Negros of possible 8.2 quake

By Glazyl M. Jopson

BACOLOD CITY – Negros Island is not spared from the threat of a massive earthquake, as the Negros Trench is capable of generating a tremor of up to magnitude 8.2, according to the Philippine Institute of Volcanology and Seismology (Phivolcs).

In a media briefing on Monday, Phivolcs Director Teresito Bacolcol said that if such an event occurs and is shallow, it could generate tsunamis that would affect the western coastlines of Negros, Panay, and even parts of Zamboanga and Palawan.

The briefing was held during the “Handa Pilipinas Exposition 2025 – Visayas Leg” at the SMX Convention Center here on Monday.

He emphasized the need for people, especially those living along coastlines, to know the natural signs of an impending tsunami.

Drawing from experience with the Cotabato Trench, it took about five minutes from the main shock before the tsunami arrived, he said.

“Even if you’re inland but happen to be at the beach when it happens, you must know the three natural warning signs: strong ground shaking that makes it hard to stand, a sudden drop in sea level, and a roaring sound from the sea. Even if only one of these signs is present, move immediately to higher ground—don’t stop to take photos or videos,” he warned.

He stressed that tsunami awareness should not be limited to coastal residents.

Bacolcol added that an earthquake of such magnitude could reach Intensity VIII and affect much of Negros Island.

“We need to be prepared. There are other parts of the country where even bigger earthquakes could occur,” he said.

Sipalay City, Negros Occidental, was rocked by a 5.1 tremor early this month, causing minor cracks in some structures and allegedly triggering the collapse of a mountain slope, raising fears of a sinkhole in Barangay Mambarato two weeks ago.

Department of Science and Technology (DOST) Secretary Renato Solidum Jr. also clarified that the so-called “Big One,” often used by media, refers to a potential massive earthquake from the West Valley Fault that could rock Metro Manila and nearby provinces.

However, he stressed that other regions across the Philippines also face significant earthquake risks.

“We’ve studied many cities in the country and prepared hazard maps and different scenarios used in earthquake drills quarterly,” Solidum said.

Solidum also explained that the recent occurrences of typhoons, earthquakes, and volcanic eruptions are not directly connected.

“These volcanoes were already showing signs of activity before the earthquakes occurred. However, in some cases, earthquakes can trigger volcanic eruptions—like what happened with Mount Pinatubo in 1991,” he noted.

Recently, both Taal Volcano and Kanlaon Volcano have erupted.

Bacolcol said Kanlaon’s current activity is part of its ongoing sequence under Alert Level 2, and that ash emissions and minor eruptions could still happen even if it is lowered to Alert Level 0.

“The threat of a major eruption remains, which is why no one should enter the four-kilometer Permanent Danger Zone (PDZ),” Bacolcol reminded.

Kanlaon Volcano, situated in Canlaon City, Negros Oriental, erupted moderately on the night of Oct. 24, and a series of ash emissions have occurred.

Though no evacuation was implemented, residents were cautioned to be vigilant.