Phivolcs: keep 5-meter no-build zone on both sides of faults

By Rjay Zuriaga Castor

ILOILO CITY – The Philippine Institute of Volcanology and Seismology (Phivolcs) is urging property owners, developers, and local government units to strictly observe the mandatory 5-meter no-build buffer zone on both sides of active fault traces, warning that even slow ground movement can damage structures over time.

Rhommel Grutas, a supervising science research specialist at Phivolcs, said the required setback, also known as the fault avoidance zone, is intended to prevent buildings from being constructed directly over or too close to active faults, where surface ground rupture may occur during an earthquake.

“If the property is transected by an active fault, a no-build buffer zone of at least five meters on both sides of the fault must be maintained,” Grutas told Daily Guardian during the Infrastructure Forum 2026 in Iloilo City on July 29.

Grutas said the affected portions of a property may still be used for open spaces such as gardens, parks, driveways, or parking areas.

“Those areas can still be used, but there should be no structures because faults continue to move gradually even without an earthquake. A fault is already a zone of weakness, so it undergoes continuous creeping movement,” he said.

He noted that slow fault movement can gradually displace fences, deform roads, and create uneven ground surfaces even without major earthquakes.

Grutas emphasized that integrating geological hazard information into infrastructure planning has become increasingly important as development accelerates across the country.

He said Phivolcs maintains online platforms that identify nearby active faults and simulate the potential impacts of earthquakes on communities and infrastructure.

He encouraged local governments, planners, engineers, and developers to make full use of the agency’s hazard assessment tools, including GeoRiskPH and FaultFinder, to evaluate earthquake hazards before approving projects.

Grutas also expressed Phivolcs’ support for updating the country’s building regulations by replacing Presidential Decree No. 1096, or the National Building Code of the Philippines, with the proposed Philippine Building Act.

He said the existing law needs to keep pace with current engineering practices and disaster risks.

The proposed measure aims to institute an all-hazards approach to structural resilience, tighten contractor and professional accountability, and modernize building regulations across the country.

“We (Phivolcs) support the revision or updating of the National Building Code. The proposed Philippine Building Act will not only streamline the processing of building permits but also strengthen compliance checks to ensure designs meet updated safety standards,” he said.

Grutas said the reform should be holistic, covering not only structural safety but also electrical systems, permitting procedures, and other technical provisions under the building code.

He added that Phivolcs is also working on the ongoing updating of the National Structural Code of the Philippines (NSCP), which contains the country’s structural and earthquake engineering requirements.

“The updated NSCP is expected to be released either later this year or next year. The revision will incorporate updated earthquake hazard levels, adopt spectral hazard maps for structural design, and align the country’s seismic provisions with the latest international standards,” he said.

“The current 2015 NSCP still relies on seismic parameters based on the 1997 Uniform Building Code, so this update will reflect more recent advances in earthquake engineering and hazard assessment,” Grutas added.

Presidential Decree No. 1096 has governed construction in the Philippines since 1977, making the country’s principal building law nearly five decades old.

The House of Representatives approved its version of the replacement measure in December 2025 on a vote of 280-0, and the bill is pending in the Senate. Sen. Raffy Tulfo filed a Senate counterpart in late May 2026, days after a nine-story building under construction collapsed in Barangay Balibago, Angeles City, Pampanga, killing at least four workers.

Panay Island carries its own exposure. The West Panay Fault runs through the western portion of the island, passing through Iloilo municipalities including Alimodian, Leon, Igbaras, and Janiuay before extending north into Capiz and Aklan. The Negros Trench faces Iloilo’s first district, and the West Panay Fault is capable of generating a magnitude 8 earthquake, as it did in the 1948 Lady Caycay quake that struck Panay.

The NSCP is published by the Association of Structural Engineers of the Philippines and serves as the technical reference for structural design nationwide. Its 2015 edition remains the operative version.