All areas located along the six active trenches in the country, including the Philippine Trench barely 150 kilometers east of Catanduanes, could experience an earthquake of up to 8.2 in magnitude, the Philippine Institute of Volcanology and Seismology (Phivolcs) said recentlty.
These trenches are the Philippine Trench (located from East Luzon to Southeast Mindanao); East Luzon Trough; Manila Trench; Negros Trench; Sulu Trench; and Cotabato Trench.
In an interview with the Philippine News Agency, Phivolcs Director Teresito Bacolcol said any place located along an active trench could possibly experience a very strong earthquake.
As earthquakes occur without warning, he advised coastal communities to immediately evacuate to higher ground when a strong tremor strikes due to the possibility of a tsunami.
A strong shaking, sudden drop or rice of sea level, and a roaring sound are three signs of an impending tsunami, Bacolcol warned.
People living in coastal communities should run to higher ground once they observe any of these signs, he added.
According to Phivolcs, a trench is the deepest portion of the sea floor and is described in technical terms as a subduction zone or a structure that manifests when a part of the earth’s crust, called a tectonic plate, moves or is pushed under another.
The Philippine Trench stretches from Bicol down the eastern coasts of Eastern Visayas and Mindanao and has a total length of nearly 1,300 kilometers and a width of about 30 kilometers.
It produced earthquakes with magnitude as high as 7.4 in 2023 and 2025, with the strongest an M8.3 event in 1924, which is approximately three times more powerful than the 7.8 temblor that struck Sarangani province recently.
In the last 50 years, two earthquakes of more than 7.0 magnitude have struck near Catanduanes.
On Jan. 11, 1982 at 2:10 PM, a 7.3 magnitude earthquake was traced to an epicenter just four (4) kilometers southwest of Gigmoto at a depth of 45.7 kilometers.
The Phivolcs reported that the earthquake injured several people and caused some damage ca in Virac while shaking was experienced as far as Baguio and Surigao provinces.
Six years later, at 11:52 AM of Feb. 24, 1988, a stronger earthquake with M7.3 occurred 37 kilometers ESE of Bato at a shallower depth of 24.9 kilometers.
According to the United States Geological Services (USGS), this quake released an estimated seismic energy equivalent to 84 atomic bombs.
A total of 1,200 earthquakes with a magnitude of four or above have struck within 300 km of Bicol in the past 10 years, for an average of 120 earthquakes per year, or 10 per month, with an earthquake hitting the region roughly every 3 days.
The last strong quake to hit the island was on Oct. 2, 2024 at 5:19 AM when an M5.9 struck 81 km northeast of Bagamanoc.