A tsunami warning remained in force along eastern Mindanao on Tuesday morning after an M8.2 earthquake struck offshore at 03:41 local time. The first surge reached the port area of Mati at about 05:06, with a tide gauge recording a 2.1-metre (6.9-foot) rise above the normal level, according to the National Sea Warning Centre.
At 06:20, the centre’s director, Louvenia Mertz, resigned by phone, then gave an interview from a temporary monitoring post in Davao City. She said her office had been directed to describe the threat as “moderate” despite new modelling showing the rupture may have shifted more seabed than first estimated. The government said the warning remained active, but that there was no basis for a wider evacuation.
Mertz, a former cargo pilot who trained in New Zealand before becoming a geophysicist, said the decision was not a prediction that another earthquake would strike. “The danger is the water already in motion,” she said. “Our first readings do not tell us what the next crest will do.”
A rupture too wide to measure
The quake’s rupture zone may stretch about 190 km (118 miles) along the Philippine Trench, said Anna-Lisa Holmqvist, a seismologist at the fictional Eastern Visayas Marine Institute who reviewed the public tide-gauge data for this report. The centre’s initial model assumed less seafloor displacement; a higher estimate puts possible run-up at 2.5 to 4.1 metres (8.2 to 13.5 feet) on exposed sections of the coast.
Holmqvist said tsunami waves often arrive in a train, with later surges stronger than the first. She cautioned that the high-end figure was a scenario, not a precise forecast, but said the uncertainty justified keeping coastal roads clear and moving people to higher ground. The centre’s gauges had recorded continuing oscillations at three sites east of Mindanao.
“A small first wave is not an all-clear, and the clock does not stop when the first wave passes.” — Anna-Lisa Holmqvist, seismologist
The government’s emergency spokesperson, Patrice B. Beaudoin, said the recorded wave had stayed below the centre’s initial ceiling and urged residents to follow local evacuation instructions rather than circulate unverified forecasts. The office said 31,000 people had been asked to leave low-lying areas in five coastal municipalities, and that the warning would be reviewed at 09:30.
Evacuation line moves inland
In Mati, local officials directed people away from the waterfront and toward school buildings on higher ground. Tom Harrison, who helps coordinate a municipal fishing cooperative, said some boat owners had secured vessels inland while families carried water and documents uphill. “The first wave looked manageable from the road,” he said. “That is exactly why people are tempted to go back.”
Mertz said the resignation followed repeated disputes over how uncertainty should be described to the public, not a disagreement about whether the quake occurred or a tsunami was under way. She said she would remain available to the centre’s technical staff, but would not withdraw her warning that a higher wave remained possible.
The warning applies to the eastern coast through Tuesday evening, with the next public bulletin due after fresh readings from the tide gauges. Officials have told residents not to return to beaches or harbours until the alert is lifted. Holmqvist said the immediate test would be whether the next several hours of measurements match the lower forecast; until then, she said, the coast should be treated as exposed.
