Local government units and the communities along the 100-kilometer West Valley Fault System may now get a clearer picture of the risks they face in the event of a powerful earthquake after the Philippine Institute of Volcanology and Seismology (Phivolcs) yesterday distributed an atlas showing in detail areas traversed by the major fault line.
Phivolcs handed copies of the Valley Fault Atlas, a handbook of large-scale maps, to local government officials to make sure that areas traversed by active faults are avoided as sites of houses and other structures.
The West Valley Fault has the potential of generating a devastating magnitude 7.2 earthquake in Metro Manila and nearby provinces.
Phivolcs director Renato Solidum warned the West Valley Fault, which traverses parts of Metro Manila and adjoining provinces of Bulacan, Laguna, Rizal and Cavite, is ripe for a possible strong earthquake.
“It can happen within our lifetime,” Solidum said.
Solidum said the West Valley Fault moves every 400 to 600 years. The last time it moved, he said, was in 1658 or 357 years ago.
Sooner or later
Solidum said the magnitude 7.8 earthquake that recently claimed thousands of lives in Nepal was expected to strike sooner or later.
“Geoscientists in Nepal presented a very similar study weeks before the magnitude 7.8 earthquake hit the country. They announced that segments of a fault near Kathmandu can move. They said the fault moves every 750 years and its last movement was in 1344 or 671 years ago,” he said.
Solidum noted that many of the damaged structures in Nepal were poorly constructed or very old structures.
The 120-page Valley Fault System in Greater Metro Manila Areas Atlas has 33 maps for every city and municipality.
The 22 maps for Metro Manila showed details of subdivisions and thoroughfares relative to the fault line and other land fissures due to its 1:5,000 scale.
Phivolcs said the maps released 15 years ago were of a bird’s eye view with a 1:10,000 scale and did not show names of subdivisions and roads.
“You can use this if you want to know if you are near a fault. Now they can see where they are,” Solidum said.
However, he said the 10 map sheets for Laguna and Rizal were still at a 1:10,000 scale since the National Mapping and Resource Information Authority did not have more detailed base maps for these areas.
The one map sheet for Bulacan and Rizal has a 1:50,000 scale.
Over 37,000 possible deaths
A recent study conducted by state agencies and the Australian government, dubbed “Greater Metro Manila Area (GMMA) Risk Analysis Project (RAP),” showed that a magnitude 7.2 earthquake along the West Valley Fault could cause P2.4 trillion in building damages and kill 37,054 persons.
Solidum said ideally the fault line should be cleared five meters on both sides.
“We encourage local government units to put the markers. It will be good but Phivolcs won’t do it,” he said.
The West Valley Fault traverses Quezon City, Marikina City, Makati City, Pasig City, Taguig City and Muntinlupa City in Metro Manila; the municipalities of Doña Remedios Trinidad and Norzagaray and San Jose del Monte City in Bulacan; Rodriguez municipality in Rizal; San Pedro City; Biñan City, Sta. Rosa City, Cabuyao City and Calamba City in Laguna; and the municipalities of Carmona, General Mariano Alvarez and Silang in Cavite.
Nearly 10 schools in danger
Phivolcs said no major commercial sites, hospitals and condominiums, sit on the fault line.
However, Solidum said they informed less than 10 schools that they are on the fault line.
“We told them they can use the buildings but they should not let students use them. It’s up to the Department of Education whether that’s followed,” he said.
Solidum advised those who plan to buy lots to check the map first.
He said the public can download maps of their locality from the Philvolcs website www.phivolcs.dost.gov.ph .
The Valley Fault System Atlas is one of the components of the Australian Aid Program-funded GMMA Ready Project, which was launched in 2012.
While earthquakes cannot be predicted, the Phivolcs head underscored the importance of preparedness and response during disasters.
“Earthquake preparedness is not an overnight activity, it should be done for several decades,” he said.
Quezon City Mayor Herbert Bautista, for his part, is asking the Department of the Interior and Local Government (DILG) and the National Housing Authority (NHA) to prioritize the relocation of those living on top of the West Valley Fault.
In a statement yesterday, Bautista said that while he understands the priority given by the DILG and NHA to relocate those living in waterways, there is also a need to give attention to families in areas on top and near the fault line. – With Janvic Mateo