STRONG MOTION STATION.  Phivolcs Director Renato Solidum, Jr. says the station can record very large ground motion during high magnitude earthquake events. The data can be used by engineers to guide them in developing designs to make buildings earthquake-resistant. (Photo taken during the virtual presser on Feb. 23, 2021

MANILA – The Philippine Institute of Volcanology and Seismology (Phivolcs) inaugurated on Tuesday the country's 100th strong motion station in Tanay, Rizal.

This is part of the Philippine Strong Motion Network (PSMNet) project that started in 1992 with only four strong motion instruments.

Phivolcs director Renato Solidum Jr. said the strong motion station can record very large ground motion during high magnitude earthquake events. Every station was strategically located in densely populated areas and near active faults.

"This (station) will enable them to determine the effects of the earthquake to buildings. It will also provide information about the earthquake rupture," he said.

Solidum noted that the new station can help Tanay identify the type of materials underneath the soil, which will help guide engineers on the design of buildings they will put up.

"The type of materials such as soft soil, stiff soil, rock beneath the surface can be characterized by earthquake signatures recorded by the strong motion station. Data from earthquake record can give idea on the predominant period of ground motion -- how fast or slow the ground vibrates; and ground acceleration which are used by engineers to develop an appropriate design to make the buildings earthquake-resistant," he said.

The Phivolcs chief also pointed out that engineers should not only consider the site specific ground shaking when putting up a building.

They must ensure that the proposed building will not move with the same speed as the ground shaking, he said.

"If we talk about shaking due to an earthquake, a building will move back and forth. If they move at the same period or speed, the building will experience longer shaking before it stops moving, and this may cause the building to be damaged," Solidum said.

Meanwhile, Metro Manila, Central Luzon, Batangas and Bicol Region could also benefit from the 100th station as this can detect strong motion as far as 300 kilometers, Phivolcs supervising science research specialist Rhommel Grutas said.

Phivolcs spent about PHP1.2 million for the facility and the equipment. The cost does not include its maintenance.

For this year, strong motion stations are set to be put up in Baler, Aurora; Malolos, Bulacan; and Davao Region, Grutas said. (PNA