Phivolcs eyes setting up of 10 tsunami detection stations

The Philippine Institute of Volcanology and Seismology (Phivolcs) is planning to put up 10 real-time local tsunami detection stations nationwide in the next five years as part of measures to create a local tsunami warning system.

However, the agency needs to generate P25 million in order to realize its plan to establish real-time tsunami wave detection stations in strategic sites across the country.

During a seminar for the media on tsunami awareness initiated by the Department of Science and Technology (DOST)-Phivolcs last Wednesday, Phivolcs deputy director Dr. Bartolome Bautista said the early establishment of a local tsunami warning system is important.

He also said putting up this system is among Phivolcs’ priority projects because "the threat of tsunami is real and highly probable in the Philippines."

"The recent tsunami disaster in the Indian Ocean emphasized the need to prepare to lessen the impact of future tsunamis (to the country)," Bautista said, referring to the Dec. 26 tidal wave last year that swept away hundreds of thousands of lives.

The Philippines currently relies on existing warning systems of the Pacific Tsunamis Warning Centers for distant or trans-Pacific tsunamis, but transmitting information on incoming tsunamis from the PTWC to Phivolcs to the public would take time.

Locally, Phivolcs uses the occurrence of earthquakes to detect a possible incoming tsunami. The agency has a seismic monitoring network consisting of 30 satellite telemeter stations with near real-time data transmission and 34 manned stations equipped with radios and telephones for non-real time data transmission.

"However, important elements of an effective local tsunami warning system include a dense, real-time network of seismic stations for accurate detection, location and evaluation of tsunami potentials of earthquakes, and real time sea level monitoring network of tsunami wave detection and confirmation," Bautista said.

He said a rapid communication system for relaying alert and warning information from the warning center to the local authorities and the public is important, as well as the availability of accurate hazard maps indicating inundation areas, shortest escape routes, and safe evacuation sites; local mass alerting system; and a well-informed citizenry to ensure proper action and response.

Phivolcs, under its director Dr. Renato Solidum, is currently fast-tracking the hazard maps for a tsunami evacuation plan.

The hazard maps include the detailed near shoreline bathymetry to accurately model focusing and defocusing effects of tsunami; high resolution topographic maps of coastal areas with 1:5,000 scale with one-meter contour interval to accurately model tsunami inundation; information on roughness of coastal areas; and location of risk elements from very recent aerial photographs.

"Public education is a must to ensure proper response during earthquake and tsunami emergencies and prevent high loss of lives," Bautista said. "The national and local media have a very important role not only rapidly disseminating warning information but also in promoting awareness and educating the public."

Under the proposed real-time tsunami wave detection stations, tsunami wet sensors — which have a simple, robust, and less expensive design than tide gauges — will be deployed to elevated points on the shore.

Bautista said through this, Phivolcs would be able to do a rapid assessment and confirmation of tsunami threats, warn areas that are far enough from the source, accurately assess severity of impact in different areas through immediate identification of actual tsunami height, and have immediate information for prioritizing rapid deployment of rescue and relief operations.

"The civil works required (for the proposed tsunami detection system) is less expensive than constructing a stilling well for tide gauges," Bautista said.

He pointed out that "the proposed usage of the existing Phivolcs seismic communication system, which is the only sophisticated part of the system, will substantially reduce the total cost of the warning system and is expected to be highly sustainable since Phivolcs engineers are already familiar with the installation, repair, and maintenance of the system."

However, Phivolcs admitted that among the disadvantages of the proposed project is that data are only generated during an actual tsunami and history of sea level fluctuation for ocean tide study could not be obtained; and that it is highly dependent on presence of small islands near an earthquake source region for early detection.

Solidum said each of the 10 tsunami detection stations will cost P2.5 million. The government of Finland is already funding the first station, located at the Lubang island group in Mindoro Oriental province.

Phivolcs has P25 million for its annual operating expenses "which we give to our observatories," Solidum said. "We continue to seek assistance from other funding institutions (for this project)."

There have been about 37 earthquakes since 1589 that generated tsunamis in the country. The largest tsunamis occurred in the Sulu Sea and Celebes Sea area while Calauag Bay, Caraga Bay, Moro Gulf area, and Manila Bay had more than one tsunami report.

Four local tsunamis that happened in Sulu Sea, Lebak, Moro Gulf, and Mindoro were considered damaging, as the highest tsunami height reached nine meters.

The 1960 Great Chile Earthquake affected the Philippines some 24 hours to 26 hours after the event, resulting in a tsunami that killed more than 20 people.