ITCZ rains elevate quake-hit Leyte’s landslide risk

MANILA-- Rainfall from the inter-tropical convergence zone (ITCZ) affecting the Visayas, possibly until late this week, may trigger landslides in earthquake-hit Leyte province's hilly and mountainous areas.

Seeping of rain into ground crevices there will help loosen the soil and make this material more prone to erosion, noted science research specialist Analyn Aquino from Philippine Institute of Volcanology and Seismology (Phivolcs).

"Aside from aftershocks, rain may set off landslides in Leyte's hilly and mountainous areas," she said.

In its 24-hour forecast released Monday, Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) forecast cloudy skies with light to moderate rains and thunderstorms in the Visayas where Leyte is as well as in Bicol, Mimaropa, Northern Mindanao and Caraga regions.

PAGASA said ITCZ is affecting the Visayas, Mindanao and Palawan province.

"ITCZ may prevail there until around Thursday (July 13)," said PAGASA weather forecaster Benison Estareja.

He noted ITCZ's expected light to moderate rains are generally unlikely to cause landslides and flash floods.

Those rains may trigger landslides in areas events like earthquakes already rendered susceptible to these slips of earth mass, he clarified.

Aquino echoed the warning, noting the risk for landslide increases if rainfall occurs in areas last week's magnitude 6.5 Leyte earthquake and its aftershocks affected already.

She said expected rains, future aftershocks or both can further disturb soil in such geologically compromised areas, raising the possibility for landslides there.

The mountainous area between Ormoc City and Jaro municipality is particularly at risk as Philippine Fault's Leyte segment runs along this location, Aquino continued.

"There are already reported sightings of landslides there," she said.

She noted Phivolcs experts are assessing ground conditions in areas last week's Leyte earthquake affected.

Earlier, Phivolcs located the earthquake's epicenter in the mountainous area between Ormoc and Jaro.

Phivolcs said ground-shaking from that earthquake and its aftershocks may have resulted in tension cracks along slopes of Leyte's hilly and mountainous areas, making these locations more susceptible to landslides.

People must avoid such areas, said Aquino.

National Disaster Risk Reduction and Management Council said in its July 9, 2017 situation report a landslide was reported in Mt. Amandiwing in Jaro's Bgy. Rubas.

According to Phivolcs, movement of Leyte segment triggered the Leyte earthquake last week.

Phivolcs said the 9:41 a.m. aftershock was a magnitude 5.4 earthquake of tectonic origin that struck at a depth of 6.0 km.

"That's the earthquake's strongest aftershock so far," said Phivolcs science research analyst Bong Lauron.

He said movement of Leyte segment triggered such record aftershock.

Lauron said Phivolcs already recorded, as of 10 a.m. Monday, 629 aftershocks of last week's Leyte earthquake.

Those aftershocks were mostly concentrated in Leyte's Ormoc-Jaro area, he noted.

He added the aftershocks' magnitudes ranged from 1.5 to 5.4.

Source: Philippines News Agency