4 cities, towns in Cebu quake risk – DENR-7

CEBU, Philippines - The Department of Environment and Natural Resources-7 has found at least four areas in Cebu that are susceptible to earthquake hazards following its recent subsidence hazard assessment.

The areas were identified as the municipalities of Oslob and Santa Fe and the cities of Bogo and Lapu-Lapu. The DENR-7 noted “collapse, suffusion and solution type of sinkholes” in these areas.

According to DENR-7, these are among the 100 areas in Cebu Province currently monitored by the Mines and Geosciences Bureau due to reported sinkholes.

“These areas are characterized by porous, coralline, bedded to massive limestone of Carcar of which formation sometimes intercalated with mari and grades into rubbly to conglomeritic limestone,” read the assessment.

Aside from inherently porous, DENR also noted that limestone in these areas is characterized by the presence of solution cavities, sinkholes and caves.

These features make limestone susceptible to ground subsidence hazards and could be triggered by earthquake and the like.

MGB-7 Chief Geologist Al Emil Berador said there are numerous sinkholes and probable sinkhole sites they are monitoring in the province, including Cebu City.

Berador said there are reported sinkholes in Barangay Guadalupe which are being closely monitored.

MGB officials advised local chief executives to be always vigilant and implement the subsidence map.

The presence of sinkholes is part of the agency’s Subsidence Mapping which commenced late last year.

MGB is eyeing to finish the subsidence hazard mapping by next year.

Moreover, MGB-7 has also completed the coastal geohazard mapping and assessment of the first seven municipalities and cities which showed vulnerability against coastal degradation brought about by climate change and other potential coastal hazards such as beach erosion, landslide/cliff collapse, sea level rise, wave attack, storm surge and tsunami.

The seven municipalities include Samboan, Santa Fe, Madridejos and Bantayan in Cebu; Dauis and Panglao in Bohol; and Dumaguete City in Negros Oriental.

According to study, storm surge is susceptible and most likely to occur in coastal areas with gently sloping seabed and those facing the open sea.

DENR-7 Director Isabelo Montejo stressed the importance of the conduct of coastal geohazard mapping and assessment in identifying areas with extreme coastal hazards potential, conduct a meeting with the LGU concerned and advice for relocation.

“Geohazard cannot be totally prevented but their impact on people and the environment may be lessened or mitigated. However, in some cases, geohazards can also be induced by human activities,” he said.

Geologic hazard or geohazard mapping and assessment program comprises three major activities— rapid assessment survey to generate geohazard maps that will indicate which areas are prone to natural dangers like landslides, flooding and ground subsidence; printing and reproduction of maps, manuals and information materials for public dissemination; and conduct of seminars and workshops for local government officials and public school teachers to increase their awareness and preparedness on various natural hazards, as well as teach them on the proper use of the geohazard maps.

“It is very important that these maps that we came up after thorough assessment will be translated to a more comprehensive way to let public easily understand the things they have to do to lessen these geologic hazards present in their respective areas,” Montejo explained.

According to Montejo, the municipalities with completed geohazard mapping and assessment are Santa Fe, Bantayan, Madridejos, Daanbantayan, Medellin, San Remigio, Tabogon, Tabuelan, Tuburan, Borbon, Sogod, Catmon, Liloan, Poro, San Francisco, Tudela, Pilar, Samboan and the City of Bogo.

The cities of Tagbilaran and Dumaguete, on the other hand, have also been subjected to vulnerability risk assessment  to optimize the usefulness of the geohazard map and aims to assess highly critical and priority areas in the region. — (FREEMAN)