TSUNAMI: MINDORO'S 1994 EXPERIENCE
MANILA, January 10, 2005 (STAR) By Felix De Los Santos - Residents of Mindoro island are still haunted by memories of the tsunami that claimed 41 lives, many of them children, on Nov. 15, 1994.At 3:15 a.m. on that day, a magnitude 7.1 earthquake jolted them awake, triggered by the movement of a previously unacknowledged active Aglubang River Fault.
People living in villages along the 40-kilometer northern shore of the island, from Puerto Galera to Pinamalayan, first heard a gush of water less than five minutes after the earthquake.
According to the Philippine Institute of Volcanology and Seismology (Phivolcs), the areas hardest hit by the tsunami were Barangays Malaylay, Old Baco, Wawa and Baco islands, where waves at least six meters high smashed into the shore, destroying 1,530 houses.
The tsunami left 41 people dead by drowning, most of them elderly or children below 10 years old.
Most of those interviewed by members of Phivolcs’ Quick Response Team said there were at least three large waves, with the first the strongest and largest.
According to Phivolcs’ investigation, the tsunami knocked down trees and inundated coastal areas as far as 250 meters inland, scoured much of the shallow sandy foreshore of Malaylay island to Wawa and formed a "beach ridge" about a kilometer long along the coast of Wawa, Old Baco and Malaylay.
Former Phivolcs director Raymundo Punongbayan said compared to the magnitude 7.8 earthquake that rocked Northern Luzon on July 16, 1990, the Mindoro quake "was weaker and less destructive but nonetheless dramatic and can be considered another classic."
"Both events were tectonic in origin, related to movement along zones of weakness transecting the Philippine archipelago, the former along the well-known Philippine Fault Zone and the latter along a hitherto unacknowledged active fault which we are now calling the Aglubang River Fault," Punongbayan said in his report on the Mindoro quake.
He also said that the Mindoro earthquake produced "geologic features such as fault-related ground rupture and secondary ground failures like liquefaction and landslides, though these were minor compared to those brought about by the 1990 Luzon earthquake."
Punongbayan pointed out that unlike the 1990 earthquake, the 1994 temblor generated a tsunami that "accounted for majority of the casualties and wrought significant damage on the northern shoreline communities of Mindoro."
The results of the investigation show that the 1994 event affected 22,452 families in 13 out of 15 municipalities — a total of 273 barangays — in Oriental Mindoro, with 78 confirmed dead and 430 more injured.
The combined effects of the earthquake and the tsunami totally destroyed 1,530 houses and partially damaged 6,036 more. Most of the houses that were totally destroyed were in the municipalities of Calapan and Baco, while most partially damaged houses were in Naujan and Gloria.
Officials placed the cost of rehabilitating 24 bridges and 500 kilometers of roads at P5.15 million.
Punongbayan said without the tsunami, the earthquake would have claimed only 29 lives. However, he acknowledged that interval between the earthquake and the tsunami is too short — between two to five minutes in the case of the Mindoro disaster — for any meaningful warning system.
"Other options must therefore be considered to reduce tsunami disaster in the future. One option is to adopt and enforce policies regulating settlements in areas exposed to tsunami, another is to install mitigation structures, but these must be weighed against the fact that tsunami-gathering events are rare and far between," he said.
A less costly alternative, according to Punongbayan, is to conduct education and information campaigns to make residents of coastal villages aware of the hazards posed by tsunamis.
"They should take any strong earthquake as a natural warning for tsunami and immediately flee toward pre-identified places of safety whenever they experience extremely strong ground-shaking," he said.
Reported by: Sol Jose Vanzi
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