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Earthquakes are impossible to predict but based on historical records, Metro Manila's West Valley Fault is due for the Next Big One within our lifetimes.
A possible magnitude-7.2 earthquake looms around the corner if the West Valley Fault along the eastern side of Metro Manila cracks, Renato Solidum Jr., Philippine Institute of Volcanology and Seismology (Phivolcs) director warns.
The West Valley Fault runs from the heights of Sierra Madre down to Laguna. It crosses the eastern side of Quezon City, western side of Marikina, western part of Pasig, eastern part of Makati, parts of Taguig, and Muntinlupa.
The fault has moved four times in the past 1,400 years. On average, it moves every 400 years, “+/- 10 to 100 years, maybe,” Solidum says. The last time an earthquake occurred along the West Valley fault was in 1658, around 355 years ago.
“It can happen within our generation or the next generation,” Solidum says.
All of Manila shaking
The earthquake can occur anywhere along the West Valley Fault, including Metro Manila. But a 7.2 magnitude earthquake can shake the ground even a hundred kilometers away, which means that it can shake the whole of Metro Manila and its surrounding provinces.
Solidum reiterates that weak, poorly-designed, and poorly-constructed buildings far from the earthquake fault are still vulnerable to destruction.
Grounds can also be affected by liquefaction, a process where loose, sandy sediments behave like liquid, Solidum explains. It becomes weak. This can cause poorly designed or constructed buildings and homes to subside or tilt, roads fissured, and water banks broken.
Areas near the waters like Marikina Valley down to Manila de Ba-i, and the coastal cities of Metro Manila are also more likely to experience stronger ground shaking due to the softer ground they sit on.
Preparation remains best option
Unlike storms and typhoons, earthquakes cannot be “forecasted” and can only be predicted by looking at how often it happens in history. To date, there are no scientific instruments that can predict when an earthquake will occur.
Solidum says that the possibility of a movement from the West Valley Fault is more than enough reason for us to prepare as soon as we can.
The most important preparation measure, Solidum says, is to make sure that buildings, houses and infrastructures in Metro Manila are earthquake- and fire-resistant.
He also says that at the local level, the structural integrity of the buildings should be assessed. “The issue though is some of the buildlings are non-engineered and most likely walang permit so they have to focus on that also,” he adds.
Major lifelines like water and power supply and communication means should be strengthened and made fire- and earthquake-proof.
Another is to have an efficient relief and recovery system after the earthquake. Solidum suggests a “bayanihan” style of relief and recovery where provinces unaffected by the earthquake should help those who are unaffected.
“Preparedness need not only be concentrated in Metro Manila and the surrounding provinces, but [also to] the other regions.”
First aid and rescue should be available in each community in case major assistance cannot immediately arrive in their area after an earthquake. — TJD/OMG/ALG, GMA News