Many landslide-prone areas in Guihulngan, says Phivolcs

Many areas of Guihulngan City are considered potentially prone to landslides during strong earthquakes, according to the Philippine Institute of Volcanology and Seismology (Phivolcs).

According to the agency’s Earthquake Triggered Landslide Susceptibility Map, areas in Guihulngan are at risk of experiencing landslides during earthquakes of intensity 6 to 8. The city is the site of a landslide that has buried houses and left 71 people missing following a 6.9 magnitude earthquake that jolted Cebu and Negros on Monday.

Geologist Perla delos Reyes, a supervising science research specialist at Phivolcs, says Guihulngan has an unstable slope and the composition of materials make it prone to landslides.

She notes old landslide scarps, or the steep surface on the undisturbed ground at the upper edge of a landslide. These indicate that historically speaking, landslides have taken place in an area, whether caused by rain or earthquake, she says.

The Phivolcs map uses colors to indicate which areas landslides could occur when a certain earthquake intensity is felt. A green area indicates that the place could experience landslide during an intensity 8 earthquake. If it is orange or pink, there could be landslides during an intensity 7 earthquake. Red means there could be a landslide at intensity 6.

Areas not susceptible to landslides during earthquakes are colored gray.

A team from Phivolcs has been dispatched to Negros to study the effects of the earthquake, including the landslide.

According to Delos Reyes, Phivolcs’ hazard maps could be used as reference by local government units when coming up with their land use plan or when constructing buildings.

She says the agency wants officials and the public to use and consult available hazard maps. “We want to educate people. It’s not a matter of knowing the hazard and then just avoiding it,” she says.

Buildings or homes may be built on areas near identified risks, but these have to be constructed properly and on the correct location, Delos Reyes says.