The West Valley Fault line and why we should care

“You don’t have to be close to the earthquake’s epicenter to be affected by it.”

Those were the words of PHIVOLCS Director Renato Solidum during SM’s Green Retail Agenda of 2014. I was reminded of what he said when he issued another warning recently about a possible “mega earthquake” that would hit areas within the West Valley Fault Line.

According to PHIVOLCS, this mega quake would be above magnitude 7. To give you an idea, the devastating earthquake in Bohol in 2013 was recorded at magnitude 7.2, leaving behind more than 200 casualties. In August 2, 1968, the Casiguran (Aurora) earthquake was at 7.3 and was felt all the way to Manila. This was the same earthquake that caused the Ruby Tower in Binondo to collapse.

Here are the cities along the West Valley Fault:

  1. Quezon City
  2. Marikina
  3. Makati
  4. Pasig (specifically Ugong and Bagong Ilog)
  5. Taguig
  6. Muntinlupa
  7. Bulacan (specifically Doña Remedios Trinidad, Norzgaray, San Jose Del Monte City)
  8. Rizal (specifically Rodriguez)
  9. Laguna (specifically San Pedro City, Biñan, Sta Rosa, Cabuyao, Calamba)
  10. Cavite (specifically Carmona, General Mariano Alvarez, Silang)

PHIVOLCS has just released a Valley Fault System Atlas . I couldn’t access the agency’s website, but you can check out Rappler’s report that includes the Atlas, which was uploaded in 7 parts.

A sample page from PHIVOLCS' Valley Fault Systems Atlas A sample page from PHIVOLCS’ Valley Fault Systems Atlas

So, what could possibly happen in Metro Manila when this strong tremor strikes? There can be faulting (fracture in rock formations), ground rupture, ground shaking, soil liquefaction, tsunami, landslide, and fire. In Metro Manila, for instance, a tsunami can go as high as 3.5 meters mean sea level if the earthquake reaches a magnitude 8.3. With the entire NCR as epicenter, key cities that are along the west valley fault line include Quezon City, Marikina, Pasig, Makati, Taguig, and Muntinlupa, Cavite, Laguna, and Rizal.

Here is an informative feature by GMA News about “The Big One” (earthquake along West Valley Fault):

Solidum said that the last strong quake in the Philippines occurred 357 years ago in 1658, and the fault line takes every 400 to 600 years to have a disturbance. Do the math.

One might say: but it’s only 2019! We can use the time we have now to get our acts together: review and update infrastructure integrity, building codes, disaster risk management plans, equipment, trainings, and knowledge. Solidum said that we have a good building code in place. The question is, is this being followed?

I’d be long gone by the time this mega quake hits us, but today’s children will be at their peak when and if this happens. I shudder at the thought.

Update: yesterday, April 22, 2019, at 5:11 pm PST, a 6.1 magnitude earthquake hit most of Luzon with the epicenter at Zambales. As of this time, 8 people were recorded dead and more injured. I experienced a stronger quake in 1991 (magnitude 7.8), but I’m more scared from yesterday’s quake for some reason. Although we have no defense against natural calamity as individuals, I still pray for everyone’s safety.

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