Phivolcs warns series of quakes off Ilocos Sur can trigger tsunami

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MANILA, Philippines — The Office of Civil Defense (OCD) on Sunday called on local disaster officials in the Ilocos, Cagayan Valley and Central Luzon regions to be on high alert and prepare for potential tsunami threats following a series of earthquakes offshore of Ilocos Sur.

The earthquakes off the coast of Ilocos Sur since last week could intensify and generate a tsunami, the Philippine Institute of Volcanology and Seismology (Phivolcs) said on Friday.

Since Dec. 17 up to 8 p.m. on Sunday, Phivolcs recorded 178 quakes, whose epicenters were clustered at approximately 100 kilometers west northwest of Santa Catalina, Ilocos Sur.

READ: Phivolcs records 86 offshore quakes in Ilocos Sur Dec 17-22

These earthquakes could either decrease in the next few days, or it could intensify and lead to a stronger earthquake, which may then generate a tsunami, Phivolcs said.

The earthquakes had magnitudes ranging from 1.8 to 5, with the strongest earthquake occurring on Dec. 19 at magnitude 5. This earthquake was reportedly felt in Santa Catalina at Intensity 2, which means the shaking was “slightly felt” based on Phivolcs’ Earthquake Intensity Scale.

According to Phivolcs, the series of earthquakes were associated with the movement of tectonic plates along Manila Trench, a long and narrow depression in the seafloor located about 60 km to 120 km west of Luzon.

Phivolcs warned that those living in coastal communities should “be aware of and monitor the natural signs of an approaching local tsunami.” These include “strong ground shaking, sudden and unusual changes in the sea level, and unusual sound.”

Should residents observe any of these signs, Phivolcs said they should “immediately move to high grounds or away from the shoreline.”

The OCD said it held an emergency meeting on Saturday to discuss contingency plans.

“Check preparations for earthquakes, with a possible tsunami resulting from the movement of the Manila Trench … I understand that your areas are not as prepared as we desire, but we must remedy this situation now,” Undersecretary Ariel Nepomuceno, the OCD chief, was quoted as telling the agency’s directors in the three regions.

Current earthquake activity indicates two likely scenarios, according to the OCD. The earthquakes would either continue at their current frequency and gradually decrease in the coming days, or they may intensify, resulting in a stronger earthquake that could trigger a tsunami.

“If our prayers are answered, we still have the chance to double our earthquake preparations—early warning systems, public awareness, drills, inventory of equipment and skilled personnel, and updating of plans. Take the lead; that’s your mission and role,” Nepomuceno said.

The National Disaster Risk Reduction and Management Council (NDRRMC) has issued a memorandum ordering the OCD regional offices of Ilocos, Cagayan Valley and Central Luzon to assess evacuation and contingency plans in response to a tsunami.

“They must identify gaps or areas for improvement to ensure alignment with the latest hazard assessments and response protocols. It is crucial to map out evacuation routes that ensure accessibility while prioritizing coastal communities with a 15-minute response time,” the NDRRMC said.