U.P. Diliman is situated near West Valley Fault Line - Government geologists

West Valley Fault Line near U.P. Diliman
Source: Phiilvolcs

MANILA, Philippines - Government geologists have found evidence of ground displacement along the West Valley Fault line, validating earlier warnings by national and local authorities that the fault - running 7.2 kilometers from Parañaque through Makati, Taguig, Marikina, to San Mateo along the periphery of Quezon City - remains active.

This came to light as the Quezon City government and the Philippine Institute of Volcanology and Seismology (Phivolcs) on Monday completed trenching work across the West Valley Fault line at Barangay Bagong Silangan, Novaliches. Intended to identify ground rupture movements and slip rates across the fault, the trenching activities found abrupt changes in sediment layers in the area, Quezon City officials said.

The activity involved excavations of two trenches, about 50 meters apart, within a 50-hectare property owned by Banco Filipino at Barangay Bagong Silangan. The area, according to a Metro Manila Earthquake Impact Reduction Study (MMEIRS), shows high susceptibility to earthquakes, along with Barangay Payatas, also in Novaliches.

The exposed trench walls indicated that at least two to three earthquake events had in fact already taken place in the area in the past. Phivolcs is now collecting charcoal pieces for carbon-14 analysis to determine the approximate time of the occurrence of the said earthquakes and the estimate of the age of the sediment layers affected by the ground displacement.

"The Phivolcs findings just validated the claim that the West Valley Fault Line is indeed active," said Elmo San Diego, action officer of the QC disaster risk reduction management council and head of the city's department of public order and safety. The MMEIRS suggests that a magnitude 7.2 earthquake may originate at the West Valley Fault line at some point in the future.

San Diego reiterated QC Mayor Herbert Bautista's call to declare the 7-kilometer stretch of the fault system that runs through QC's periphery a danger zone. "The safety of our residents, particularly those living on top of the fault line, is non-negotiable," San Diego said. "The fault line is unlivable."

The fault line cuts across major cities in Metro Manila, and has in its path scores of large subdivisions and schools. Ateneo de Manila and the University of the Philippines in Diliman are both situated near or atop the fault line which has not moved in 200 years, but which Phivolcs had warned may therefore be "ripe for movement".

Batasan Hills in the northern stretch of the fault has within its vicinity the House of Representatives of the Philippines. To the south, subdivisions such as Green Meadows, Valle Verde, and McKinley Hills all sit atop the fault. Ayala Heights in Quezon is similarly situated in an area within the potential influence of movements along the line.

(Philippine News Agency)

Relocation set for QC residents residing in faultline area

QUEZON CITY, May 1 (PIA) - The Quezon City government has ordered the immediate relocation of 42 families whose houses stand on an area transecting the West Valley Fault Line at Gen. del Pilar St. in Barangay Bagong Silangan.

The QC officials directed the QC disaster risk management council to start sending notices to the affected families to advise them to voluntarily vacate the area, which is more vulnerable to ground rupture and potential landslides should there be an earthquake generated by the fault system.

Aside from the notice, the city government will also be preparing waivers for homeowners resisting the order. “Kung ayaw nilang umalis sa kabila ng ating mga panawagan, marapat lamang na papirmahin natin sila ng waiver na walang sagutin sa kanila ang gobyerno,” QC Mayor Herbert Bautista said.

The city government is set to file an application with the National Housing Authority (NHA) for the relocation of the affected families.

Once vacated, the city intends to plant the area with trees to determine ground and soil movements.

The order for the relocation of the 42 families was based on the recommendation made by the Philippine Institute of Volcanology and Seismology (PHIVOLCS) during an inspection of the traces of the fault line at Barangays Bagong Silangan and Payatas.

To date, the city has already identified at least 900 property owners residing within the five meter- wide buffer zone recommended by PHIVOLCS.

Given the possible extent of the damage that QC would incur during the movement of the fault system, Mayor Bautista ordered the creation of the West Valley Fault Task Group to ensure public safety within the recommended buffer zone.