Government scientists are expected to start verifying today reports that sinkholes are forming in the quake-hit areas of Bohol and Cebu. With aftershocks continuing in the two Visayan provinces a week after a magnitude 7.2 earthquake struck, residents fear that their homes and even entire communities could be swallowed up by the ground.
Guatemala City has seen several sinkholes, with the largest, 20 meters in diameter and 150 meters deep, swallowing up about 20 homes in 2007. Three years later, a three-story apartment building disappeared into another sinkhole in the city with a diameter of 21.5 meters and estimated depth of 31.2 meters. A woman in the same city also found a smaller sinkhole 12 meters deep under her bed. Sinkholes have also been reported in recent years in China, the Middle East and the United States from New York to Texas and Florida.
Experts said limestone foundations are among the most vulnerable to sinkholes, making Bohol a risk area. Government scientists hope to develop a geo-hazard map of the province to provide guidance to the public. Such maps have been drawn up for areas prone to earthquakes and massive flooding.
Similar studies, and not just for sinkholes, can also be undertaken for urban centers and surrounding areas experiencing rapid development. In August 1999, after two days of incessant heavy rain, the entire Cherry Hills subdivision in San Luis, Antipolo City collapsed in a landslide. Fifty-nine people died and 32 were injured, with 379 houses in the hillside community destroyed. Experts said the ground was prone to landslides and should not have been used for residential development.
Since that tragedy, developers presumably have become more careful, at least in Metro Manila and surrounding areas. The earthquake in Central Visayas, however, should lead to wider ground risk assessments across the country.