3 churches damaged, pattern of Bohol aftershocks point south
South Cebu churches and roads bore the brunt of damage from the Oct. 15 earthquake compared to other parts of the province.
Geologists are giving the south a closer look because of the pattern of aftershocks after the 7.2 temblor, whose epicenter was across the sea in central Bohol.
Aftershock data plotted by Jessie Olaivar Floren, a Cebuano Geographic Information System expert, suggest a pattern from northern Bohol to south Cebu. (See map on page 1 and related story on page 3.)
Floren, who works as a GIS specialist in an international nongovernment organization, used raw data posted online by the Philippine Institute of Volcanology and Seismology (Phivolcs).
The pattern ties in with findings of an initial field assessment by architecture students of the University of San Carlos who inspected 45 heritage churches across Cebu.
Three churches that suffered the most quake damage were in the southern towns of Dalaguete, Sibonga and Boljoon.
They were identified as the San Guillermo de Aquitania Parish in Dalaguete, the Nuestra Señora del Pilar parish church in Sibonga and the Church of the Nuestra Señora de Parish in Boljoon town.
Architect Melva Rodriguez-Java said the other churches had minor damage, but the Spanish-era coral stone churches in these three southern towns would need experts – conservation workers, architects and engineers – to determine what to do next for repairs.
Java, director of the USC Conservation Heritage Research Institute and Workshop (USC Cherish), presented the findings last Tuesday at the university. A report will be finalized and given to the Archdiocese of Cebu and the National Commission of Culture and Arts to support any request for technical aid and funds for restoration.
“These churches are part of us. They are national patrimony. They hold our collective memories and therefore, they should be saved,” said Java.
In terms of roads, the major quake damage was reported in the Carcar bypass road (collapsed roadside protection), Carcar-Balili Road (asphalt pavement cracks) and Cebu-Toledo wharf (landslides), all in south Cebu.
Landslides were also reported in Boljoon national highway, and four barangays of Boljoon town , according to the national disaster response office.
CEBU FAULT LINES
No one can predict an earthquake but Cebu government officials don’t need to wait for one to strike before taking disaster-preparedness seriously.
Cebu island has an active fault system, which geologists call the Cebu Lineament, a two-pronged structure beneath the ground covering more than half of the island.
Robinson Jorgio, a Mactan-based seismic observer from the Philippine Institute of Volcanology and Seismology (Phivolcs), said the fault is “active” and capable of producing earthquakes.
In the last 30 years, however, the fault has produced “hardly perceptible shocks” of magnitudes less than 3.
“Based on our data, only a few earthquakes were caused by this fault and they were barely even felt,” said Jorgio.
The country has a 1,200 kilometer long fault zone “that transects the whole Philippine archipelago from northwestern Luzon to southeastern Mindanao” according to the Phivolcs website, which shows maps of fault lines appearing in each province and region (see www.phivolcs.dost.gov.ph.)
The website showed that the seismicity, or the relative frequency of distribution of earthquakes, in Cebu is quite low.
Last Tuesday, the Cebu Provincial Board listened to a Phivolcs Manila representative brief them about earthquakes. Jeffrey Perez said the focus should be on disaster-preparedness because an area can be affected by a quake even if it has no fault line.
Vice Gov. Agnes Magpale said the PB will look into new legislation that would require stricter compliance of the National Building Code, especially for school buildings.
In a separate interview, Jorgio said people should not focus on identifying fault lines, but on being ready to respond to earthquakes as intense as the Oct. 15 temblor, especially when it could originate from under the same ground they are standing on.
Cebuano residents in their 80s can’t remember an earthquake as powerful as last week’s temblor whose aftershocks are still being felt daily, a week after the first jolt.
“Since earthquakes cannot be predicted, all we can do is be prepared when they come,” said Jorgio.
Preparedness
Most deaths during earthquakes are caused by fallen debris and surrounding structures, not the quake itself, he said.
“Retrofitting” a house – providing a structure with new parts that were not available when it was originally built – would make it more sturdy, he said.
“If people should plan to build a house these days, they should make sure it’s earthquake-proofed,” said Jorgio.
As a disaster-ready step, storing food, water and other necessities good for five days is recommended.
“People should observe the “duck, cover, and hold” response during the earthquake itself,” said Jorgio.
“They should identify hazards in their houses like things that could fall or break and things that are unstable,” he said.
Phivolcs also conducts information campaigns in schools and communities.
“We really need to be prepared,” said Jorgio.
Earlier this week, Jorgio and a colleague from the Mactan seismic station planted Global Positioning System (GPS) receivers in sites around north Cebu – Catmon, Tabogon, San Remigio towns and in western Toledo City.
These devices monitor movements within the earth’s surface by comparing data gathered from each receiver placed in strategic positions all over the province.
“This will help in our observation of the fault in Cebu,” said Jorgio.
The day after last week’s earthquake, seismographs, which are used to detect earthquakes, and GPS receivers were also deployed to and planted in Bohol.
