Aftershocks

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Sunday, October 20, 2013


WE WERE at the parking lot of a mall in Tabunok yesterday afternoon when we saw the vehicles shake.
My son Edison, who has developed a feel for earthquakes, momentarily stopped walking, worry etched on his face. Some shoppers (only a few, actually) walked out of the mall in haste. They were from the upper floors where the shaking was more pronounced.

Inside, we bumped into my friend Haide, who was with her two kids. “Mopauli na lang mi.
Mag-grocery pa ra ba unta ko. Pero gikuyawan na ang mga bata human atong pag-uyog ganina.”
Welcome to life after last Tuesday’s 7.2 magnitude earthquake that devastated Bohol Province and wrought damage on some parts of the island of Cebu.

Since that quake, people in the two provinces have to adjust to life disturbed from time to time by aftershocks. If you still are clueless about them, aftershocks are those shaking that have been occurring since the main quake hit us.

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Seismologists say that aftershocks can’t be stronger than the main shock. Specifically, they say that the strongest aftershock is usually weaker by magnitude 1.2. That means that theoretically, a magnitude 6 aftershock is possible, which is still strong.

And how long would we be enduring these episodes of shaking? Weeks, months, a year, decades. Or it could even last for centuries. At least that was what Mian Liu, a geophysicist at the University of Missouri in Columbia, and Seth Stein, a geophysicist at Northwestern University in Evanston,
Illinois, once told Nature, an international weekly science journal.

“At fast-moving faults, such as the San Andreas Fault, aftershocks would die out quickly. But with
the New Madrid Fault, which moves over 100 times more slowly than the San Andreas Fault, it could take hundreds of years for the effects of a major earthquake to fade away.”

Before wallowing in worries, here’s the caveat from the website geology.com: careful studies using
“long historical catalogs” still have to be done to prove that contention. Even then, past experiences of tremors show that the duration of the occurrence of aftershocks could be long. Which means that we in Cebu and Bohol should be prepared psychologically to deal with it.

I saw a recent interview over cable channel ANC of an official of the Philippine Institute of Volcanology and Seismology (Phivolcs), who also showed the map of the centers of the aftershocks that hit one day after the major quake. They were mostly in Bohol. The second day, a couple or so of the aftershocks’ centers extended to the southern part of the sea between Bohol and Cebu. I don’t know where the centers had been days after that.

What I am saying is that aftershocks do not necessarily emanate just from the epicenter of the major quake. Thus it can be stronger in areas far from, say, Sagbayan, which is said to be near the epicenter of Tuesday’s quake. If an aftershock’s center is in, say, Tagbilaran, it could be strong in that area even if its magnitude is only, for example, 5.5.

But we could not continue running away from our fears. It’s like when terrorists plant a bomb somewhere and we begin to worry that our place would be the next target. Life shouldn’t stop because of that. Meaning we should learn how to deal with our worst fears.

It’s easier said than done, of course. But we have to do it. On that, here’s something from Canadian actor Nathan Fillion: “Saw a little girl touch a big bug and shout, ‘I conquered my fear! YES!’ and calmly walk away. I was inspired.”

(khanwens@gmail.com)

Published in the Sun.Star Cebu newspaper on October 20, 2013.

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