DUMAGUETE CITY, Philippines – The Phivolcs has issued a warning this week against people returning to their houses or taking up residence in landslide-hit areas in Guihulngan City and La Libertad town in Negros Oriental because these are now vulnerable to more ground movements that would further endanger lives and property.
Chief science research specialist Art Daag, of the Phivolcs Central Office, on Monday disclosed that the magnitude 6.9 earthquake that rocked Cebu and Negros last Feb. 6 not only caused landslides in areas of northern Negros Oriental, but also weakened the rock and soil slopes there.
Daag, who headed a team of Phivolcs experts that surveyed the post-earthquake damages, disclosed on Monday that at least four major landslides had been reported and inspected, namely, that in Solonggon, La Libertad, and those in Planas, Zamora and upper Tinayonan Beach in Guihulngan City.
The Solonggon and Planas landslides have claimed the lives of several people, with many still reported missing and believed to have been buried alive. There were other reported landslides in the towns of Jimalalud, Ayungon and Tayasan but without casualties.
Daag said the landslides in northern Negros Oriental were of a different type, describing these as deep-seated rotational and not shallow in movement. Most of the ground material in the northern quake-hit areas of Negros Oriental is basically composed of limestone, he noted.
The main shock and the aftershocks that total to almost 2,000 as of last count this week have created stresses in these mountain slopes, making them weak and vulnerable to further collapse, Daag warned.
Weight from heavy rains would also further aggravate the threat as tension cracks have also been monitored in the already weakened slopes, he said.
In the initial survey, the Phivolcs official noted that the major landslides measured between 10 to 20 hectares wide and with an estimated height of about 30 meters, or simply put, about the height of three coconut trees placed one on top of the other.
While the aftershocks continued, although with the strength and intensity getting smaller, it was not yet determined when the ground shaking would stop, Daag said, citing the major earthquake in Baguio City several years ago when the aftershocks went on for three months.
Daag and his team returned to Manila on Tuesday but assured that a comprehensive report on the damages caused by the quake will be out in two weeks. This would include survey findings and recommendations, such as preventing people from living near or on high risk mountain slopes, he said. - THE FREEMAN