‘Big One’ remains a threat — DoST

The Department of Science and Technology on Tuesday confirmed that the country experienced more earthquakes than usual in 2023, as it called for the retrofitting of old buildings, especially in Metro Manila.

In a Malacañang briefing, DoST Secretary Renato Solidum attributed the increase mainly to aftershocks from major events.

"If you count the aftershocks, yes. But there are sometimes years where we have major earthquake events, and major earthquake events trigger a lot of aftershocks," he said.

Solidum explained that a 7.4-magnitude earthquake can generate thousands of aftershocks, significantly impacting the yearly count.

As published on the DoST-Philippine Institute of Volcanology and Seismology website, the agency recorded 14,317 earthquakes in 2022 and 14,820 from January 2023 to date.

While Metro Manila is better equipped to handle the dreaded "Big One" — estimated to range in strength from 7.2 to 8 — Solidum cited the need to bolster older structures, especially in Metro Manila, which the West Valley Fault threatens.

A World Bank study had estimated that a magnitude 7.2 earthquake on the West Valley Fault could result in an estimated 48,000 fatalities and $48 billion in economic losses.

Catastrophic

The National Capital Region faces the potential of a 7.2-magnitude event due to the presence of the West Valley Fault, Solidum said, explaining that a 7.2 in the metro may be more catastrophic than the 7.4 quakes recorded in other areas.

"If we look at the scenario involving the West Valley Fault, based on its length, we can expect it to generate a magnitude-7.2 earthquake," Solidum added.

He emphasized that the shaking in Metro Manila would be significantly stronger due to the earthquake occurring on land, which could reach intensity-8 compared to the intensity-7 experienced in Surigao recently.

"At intensity 8, you cannot stand. The shaking will be kind of long, close to one minute, depending on the foundation. Intensity-7, you can stand, and there's less damage," Solidum said.

In simple terms, magnitude measures the strength of an earthquake at its source, while intensity measures the strength of an earthquake where you are. Magnitude is constant, while intensity depends on how far you are from the epicenter. The farther you are from the epicenter, the weaker you would feel the shaking.

Improved awareness

Highlighting the progress made in earthquake preparedness over the past 10 years, Solidum acknowledged that awareness campaigns have significantly improved, particularly among the younger population.

He emphasized the crucial role of information dissemination in ensuring that individuals are equipped with the knowledge to respond effectively to disasters.

While newly constructed buildings adhere to stricter building codes, older buildings require retrofitting to minimize damage and potential casualties.

"What's important is we need to continue strengthening the houses constructed years before. The new ones conform to the building code, but we need to strengthen our building preparedness. That's where the solution lies in reducing potential casualties
— we need to strengthen to minimize the affected," he pointed out.

Solidum emphasized the importance of analyzing the consequences of past earthquakes. "The important thing is the consequence of the events," Solidum said. "And if you look at past events, these events in Mindanao have not caused significant casualties."

He said most earthquakes occurring in Mindanao are due to numerous active faults and trenches in the region.