Pinatubo and the Luzon earthquake

I HOPE that we who remembered the 21st anniversary of the eruption of Mount Pinatubo this month (June 15) will also remember the 22nd anniversary of the big Luzon earthquake next month (July 16).

Both disasters changed the course of Philippine history, altered the destinies of millions of people, and claimed the lives of hundreds — 280 during the eruption and 1,621 during the earthquake.

Both occurred during the term of Cory Aquino, and both occurred within a year of each other, dealing the nation a one-two punch that nearly crippled the economy.

The magnitude 7.8 earthquake, with epicenter at Digdig, Nueva Ecija, struck at 4:26 p.m. on July 16, 1990. I remember running out of my office at Holy Angel University to find the ground undulating like the back of a giant serpent. But the scariest part was to see thousands of students and teachers screaming and weeping like little children, unable to stand so they just sat or lay on the ground. It was a scene straight out of the Old Testament.

That earthquake caused a 125-km ground rupture that stretched from Dingalan, Aurora to Cuyapo, Nueva Ecija, and created a new sub-fault that cut across Baguio City. Most hotels in Baguio collapsed, including Hyatt Terraces and Hotel Nevada, where the wife of former Central Bank Governor Jaime Laya was crushed to death.

Less than two hours after that quake, at 6:10 p.m., a magnitude 4.8 earthquake struck the Mount Pinatubo area. It wasn’t an aftershock that came from the source of the first earthquake, but an entirely different earthquake that originated in the cracks (faults) underneath Mount Pinatubo. Apparently, the Luzon earthquake was so massive it rattled the local faults around the mountain, which in turn triggered tremors of their own.

Kapampangans didn’t know it at the time, but Mount Pinatubo continued to vibrate in the next two weeks. Aetas living in the area heard rumbling sounds and saw landslides and smoke coming out of a fissure on the side of the mountain. They reported these to a Franciscan nun, Sister Emma Fondevilla, who relayed the information to PHIVOLCS on August 4, 1990.

The next day, the Philippine Daily Inquirer published a news item entitled “Zambales folk flee as mount acts up.” It was the first article ever on the Pinatubo saga.

No one took the story seriously because the nation’s attention was still gripped by the devastation caused by the July 16 earthquake, and by the dramatic rescue of survivors in the collapsed Hyatt Terraces in Baguio.

To be fair, a Phivolcs team did conduct a helicopter survey of the Pinatubo area, but it came back with the announcement that the mountain showed no sign of erupting whatsoever.

There was one scientist, though, who had doubts. Geologist Kevin Rodolfo, a Fil-Am professor from Chicago who was visiting PHIVOLCS when the first reports came in, was of the opinion that a hike up the mountain would have revealed more, instead of just a visual check from a helicopter. But he did not take it against the government agency, knowing how little their budget was and how distracted they were by Taal Volcano, which was also acting up at the time. The visiting professor ended his visit and returned to Chicago.

And so, despite those warning signs in July-August 1990, everyone forgot about Pinatubo. The idea that a little-known mountain a short distance from a huge US military base might erupt was just too far-fetched. No one had a memory that it ever erupted and scientists had never bothered to collect baseline data about its prehistoric eruptions.

The next time the nation heard of Pinatubo again was eight months later, in April 1991, when Sister Emma Fondevilla, the same nun who had made the first report in August 1990, went back to PHIVOLCS to report once again about the heavy steaming and explosions at Pinatubo. This time, Phivolcs did a ground check, and believed.

By then, however, eight precious months had been wasted and the eruption was only two short months away.

Although Phivolcs was eventually congratulated for its accurate prediction of the eruption, which saved thousands of lives, who knows how happier the ending might have been if those warning signs were heeded eight months earlier?

Most scientists who analyzed the eruption insist that Pinatubo “woke up” in April 1991, not earlier, because that was when magma intruded into the magma chamber beneath the mountain, as evidenced by the loud explosions that Aetas heard and the heavy steaming that they saw, which were reported by Sister Emma.

But remember, that was only the nun’s second report. Sister Emma had already made a first report about loud explosions and rumbling eight months earlier, in August 1990, which scientists had merely shrugged off.

Is it possible that magma may have entered Pinatubo’s chamber in August 1990 and not April 1991? Would it have made a difference as far as preparations for the eruption were concerned?

Quakes, explosions and rumbling around a mountain are all tell-tale signs that magma has seeped into cracks beneath the mountain and was pushing its way up to the surface. Steaming means the hot magma has come into contact with an underground water system.

All volcanoes have a magma chamber beneath them. Every hundred or thousand years the cycle of magma seepage and chamber reheating and reactivation occurs, but sometimes the cycle is hastened by an intervening event. In the case of Pinatubo, that intervening event was the 1990 Luzon earthquake.

Still, scientists say that after 600 years of dormancy, Pinatubo was due for an eruption anyway, with or without the Luzon earthquake.

Maybe.

But I’m one who believes that everything in this world happens for a reason. That it erupted 21 years ago and not today or tomorrow was part of a plan. What plan? Who knows? Looking at history, that was the year the RP-US Bases Agreement was set to expire, and both countries were involved in tense negotiations whether to extend it or not, until Pinatubo settled the matter.

Had the Luzon earthquake not occurred, Pinatubo might still be asleep, and the US military bases would still be in Subic and Clark. And in this age of anxiety over China, no volcanic eruption would make them pack up and leave.

But as destiny would have it, the eruption occurred at the precise moment in history when the military bases were most vulnerable: the end of the term of their lease (in 1991) and the end of Soviet Union (also in 1991).

And it occurred on the very day and hour a typhoon crossed Central Luzon the first time in recorded history that a volcanic eruption and a typhoon happened in exactly the same place at exactly the same time—which doubled the damage of the eruption.

Those spectacular coincidences made it easier for the United States to end the deal and leave us alone.