Seek safer ground, expert urges public

MANILA- An expert is cautioning against building near locations where landslide, sand boil and surface rupture occurred due to the magnitude 6.7 earthquake that rocked Surigao del Norte province this month.

Such occurrences are manifestations of geologic dangers lurking there, noted geologist Ericson Bariso from Philippine Institute of Volcanology and Seismology (Phivolcs).

"It's best to build on safer ground," he said.

He noted landslides, sand boils and surface ruptures as well as destruction of structures may recur if the Philippine Fault Zone's Surigao segment moves again, generating another earthquake in the future.

Phivolcs earlier identified the Surigao segment's movement as trigger of the Surigao earthquake this month.

People, including those affected by the earthquake, must first study geohazard maps of areas where they plan to build so they can identify geologic dangers there and be guided accordingly, Bariso said.

Landslide is movement of surface material down a slope, noted US Geological Survey (USGS).

Sand boil is sand and water coming out onto the ground surface during an earthquake as a result of liquefaction at shallow depth, USGS also said.

USGS noted liquefaction is a "process by which water-saturated sediment temporarily loses strength and acts as a fluid."

Surface rupture is crack in the ground due to a fault's movement, said Phivolcs science research specialist Kim Vitto.

Reporting on the earthquake's aftermath, Phivolcs said a landslide struck Malimono municipality in Surigao del Norte.

Phivolcs also reported monitoring a sand boil in the province after the earthquake.

The agency cited such sand boil as "coinciding the surface rupture" that occurred in the province's San Francisco municipality.

"Sand boils can occur in any area where ground condition is liquefiable - such condition is present where the rupture occurred," noted Vitto.

Phivolcs reported already recording 229 aftershocks from this month's Surigao earthquake as of 6 a.m. Tuesday (Feb. 21).

The aftershocks' magnitude ranged from 2.0 to 5.0, Phivolcs noted.

Twenty-five of the recorded aftershocks were reported felt, added Phivolcs. (PNA)

Source: Philippines News Agency

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