MANILA, Philippines — The Philippine Institute of Volcanology and Seismology (Phivolcs) has called for a manual structural audit of all structures in Metro Manila and nearby provinces that were built before 1992 to determine if they could withstand the “Big One.”
The Big One refers to a magnitude 7.2 earthquake that could be generated by the West Valley Fault, which state seismologists warned is “ripe for movement.”
Department of Science and Technology Undersecretary and Phivolcs director Renato Solidum Jr. said structures, including houses, built before 1992 might be weaker and unable to withstand strong earthquakes.
“There should be a manual structural audit of all the buildings in Metro Manila and nearby areas to ensure that the weak structures would either be retrofitted or demolished,” Solidum said.
He said in 1992 more earthquake resistance standards were included in the National Building Code.
Solidum made the appeal after the magnitude 6.1 tremor that hit Luzon on Monday damaged several structures, including a four-story Chuzon supermarket in Porac, Pampanga, which left 18 people dead.
The tremor, which was triggered by a “blind fault” in Castillejos, Zambales, was felt in many parts of Luzon, including Metro Manila.
In Manila, a building of the Emilio Aguinaldo College leaned towards its adjacent building after the quake, which many believed was due to liquefaction.
Aftershocks from the magnitude 6.1 tremor are expected to last for several weeks, according to Solidum.
Phivolcs has been warning the public of the possible magnitude 7.2 earthquake from the West Valley Fault that could kill about 48,000 people in Metro Manila, Bulacan, Cavite, Rizal, Laguna and Pampanga.
This developed as earthquakes continued to hit different parts of the country yesterday.
A magnitude 4.4 tremor struck some seven kilometers southwest of San Nicolas, Ilocos Norte at 3 a.m.
It was felt at Intensity 4 – classified as moderately strong – in San Nicolas and Intensity 3 in Sarrat, Ilocos Norte.
A magnitude 4 quake also hit seven km northeast of Albuera, Leyte at 10:44 a.m. yesterday.
It was felt at Intensity 3 in Ormoc City.
At 1:26 p.m., a magnitude 5.5 tremor struck 70 km off General Luna, Surigao del Norte.
It was felt at Intensity 2 in Surigao City.
The tremor was followed by several aftershocks, most of which were unfelt.
The National Risk Reduction and Disaster Management Council (NDRRMC) in an updated report yesterday said there are now 18 people killed in last Monday’s tremor. The number of missing persons went down to seven individuals from 14.
NDRRMC spokesman Edgar Posadas said most of the fatalities were from Pampanga, particularly from the collapsed Chuzon Supermarket in Porac town.
The number of quake-related injuries in Central Luzon – Zambales, Bataan and Pampanga – has increased to 282 individuals, while 909 families or 3,381 persons from 13 cities and municipalities were directly affected by the tremor.
Phivolcs earlier said the frequent occurrence of tremors in the country is not uncommon, considering the country’s geographical location.
Phivolcs, however, urged those who are buying new properties in the country to make use of the application that could determine if the area is near or on top of an active fault.
The application, FaultFinder, can be accessed through the Phivolcs’ website, www.phivolcs.dost.gov.ph.
Arturo Daag, Phivolcs chief science research specialist, also urged building developers to observe the five-meter buffer zones on both sides of the active fault.
Phivolcs earlier reported over 3,000 structures are exposed to ground rupture once the West Valley Fault moves. – With Jaime Laude