Luzon, Visayas, Mindanao rattled by quakes

MANILA – For three consecutive days this week, all three of the Philippines’ major island groups were hit by strong earthquakes, none of which were connected to each other.

A 6.1 magnitude earthquake shook parts of Central Luzon and Metro Manila on Monday, April 22, followed by a magnitude 6.5 temblor that hit Samar and Cebu on Tuesday, April 23. On Wednesday, April 24, magnitude 4.7 and magnitude 4.5 quakes then hit Davao Oriental and Davao Occidental, respectively.

The Luzon quake proved to be the deadliest, as at least 16 were confirmed killed as of Wednesday when the Chuzo supermarket in Porac, Pampanga, collapsed. The number is likely to increase since more than 90 were still missing as of press time, trapped under the rubble of what was once a four-storey building.

The Monday quake cause all three mass transit systems in Metro Manila – the MRT, LRT and PNR — to stop operations for the day and throughout most of Tuesday. President Rodrigo Duterte ordered all government offices to suspend operations on April 23 in order to conduct safety inspections.

Classes in most schools in Metro Manila were also suspended on Tuesday and Wednesday, although the suspension will last longer for the Emilio Aguinaldo College (EAC) along Taft Avenue because it suffered the worst damage.

Engineers were debating whether EAC could still be saved, or would have to be demolished as the main building of the college was visibly leaning at its next door neighbor following the quake.

Seismic observer Robinson Jorgio of the Philippine Institute of Volcanology and Seismology (Philvolcs) said that the Luzon, Visayas and Mindanao quakes were caused by different fault lines, and were therefore unrelated.

The temblors in the Visayas region, while stronger than the Luzon tremors, caused lesser damage. Analysts pointed out that the ground in Central Luzon was softer, which is why more structures there were damaged, including the supermarket collapse.

Power interruptions should be expected this week in Luzon, including Metro Manila, according to the National Grid Corporation of the Phils. as they check on power lines.

No serious damage was reported as of press time in both the Visayas and Mindanao quakes.

The 1990 quake which was at magnitude 7.7 was the deadliest in recent memory, but even a 7.1 magnitude temblor would cause catastrophic damage, according to Philvolcs executive director Renato Solidum.

He said that shorter buildings were actually at greater risk than taller skyscrapers.

The closer a building is to an active fault, the more prone it will be to swaying and vibration.

This was one reason that the lower EAC was badly damaged, while not a single tall tower anywhere in Metro Manila suffered similar damage.

Solidum assured that the quakes of the last three days in Luzon, Visayas and Mindanao were definitely “not related.”

The biggest threat of the so-called Big One which could be as high as intensity 8 would make the simple act of standing at ground level difficult.