October 7, 2022

The Philippine Institute of Volcanology and Seismology (Phivolcs) said last week infrastructures can still be built even in high-risk areas but with proper engineering interventions that could withstand earthquakes.

Phivolcs Supervising Science Research Specialist Rhommel Grutas said collapsed buildings is the primary cause of fatalities during earthquakes, which he said can be mitigated if builders follow the proper engineering designs stated in the National Building Code.

“If a building did not collapse, what would we do? We only need to duck, cover, and hold and then wait after the earthquake passes to get out of the building. There will be no casualties,” Grutas said. 

During the launch of the Baguio City ground shaking hazard maps on Sept. 8, Grutas said construction of new buildings could still be possible despite the city’s slope terrain.

“(The design of buildings) follows urbanization, if the population is rising, you need to build vertical structures like condominiums to accommodate people. We are not limiting the height of structures as long as it follows the proper design,” he said. 

A team from Phivolcs came out with the  Department of Science and Technology-funded project: “Passive Seismic Stratigraphy of Irregular Topography (PSSIT) Applicable to Mountainous Areas of Baguio City” which resulted to the creation of various maps. 

He said the compilation of maps provides information on the levels of ground motion and site response during strong earthquake based on the characteristics of the underlying soil and rock layers and the effects of specific topography in the mountainous terrain of Baguio City. The team also included La Trinidad, Benguet in the mapping, which is Phivolcs’ pilot areas for the project. 

The maps include predominant period microzonation map,Vs30 model map, site amplification map, peak ground acceleration map and spectral acceleration map (0.2 seconds and 1.0 sec) on rock sites.

The maps can be a reference for structural engineers in designing and constructing earthquake-resilient buildings and infrastructures in Baguio City.

A technical workshop followed during the launching to aid the participants in interpreting the data presented on the maps, identify ground conditions on-site using the publication and estimate the natural vibration of buildings to determine structures that might be vulnerable to intense ground shaking. Grutas said they hope the maps would be used by the participants in comprehensive land use and development planning and earthquake risk reduction efforts to prevent loss of lives and properties during earthquakes. The maps will be made available for download at the DOST-Phivolcs website: www.phivolcs.dost.gov.ph. – Ofelia C. Empian