Strong Luzon quake in ’90 recalled; Phivolcs boosts monitoring capability

Published July 16, 2020, 2:36 PM

by Alexandria Dennise San Juan

Filipinos recalled on Thursday, July 16, the  magnitude-7.8 earthquake that struck Northern and Central Luzon in 1990 which claimed thousands of lives and caused millions of pesos in damage to infrastructure, buildings and homes.

The Philippines is part of the Pacific Ring of Fire, an area along the Pacific Ocean where about 90 percent of the earth’s earthquakes occur according to the National Geographic.

While tremors with varying magnitudes including more minor quakes usually hit the Philippines, the so-called 1990 Luzon Earthquake was tagged as one of the most devastating earthquakes in the country in recent times.

As the 30th anniversary of the 1990 Luzon quake is recalled, it is timely to consider the lessons learned in terms as these may be reflected in our current state of disaster preparedness.

New technology

Throughout the years, Phivolcs has also strengthened its disaster risk reduction efforts through enhanced seismic monitoring capability that allows faster and more accurate delivery of earthquake information.

On Thursday, in time with the 30th anniversary of the Luzon quake, Phivolcs and multi-agency GeoRisk PH launched its latest web tool named GeoMapperPH, a web and mobile application designed to collect and update natural hazards, exposure, vulnerability, and coping capacity data.

Through this app, Phivolcs aims to empower local government units and decision-makers to make comprehensive, appropriate, and well-informed decisions and actions for disaster management.  

Last year, the state seismology bureau also came up with HazardHunterPH, a web application used to generate assessment reports on the user’s location, featuring a summary of seismic, volcanic, and hydro-meteorological hazards, along with explanations and recommendations.

Another web app released by the agency In November last year was the GeoAnalyticsPH: Tsunami Analytics, which is able to give summary reports on population, schools, and health facilities exposed to tsunami hazards nationwide. It can also calculate the total area exposed to tsunami.

Preparedness advocacy

To further enhance its preparedness on the effects of natural disasters, Phivolcs set up some decision support tools such as a tsunami scenario database and crustal deformation studies.

To prevent damage and casualties during these events, the government and other agencies ramped up its efforts to ensure that proper protocols are implemented in urban planning and construction such as the strict implementation of building codes and making sure that buildings are not constructed in high-risk areas such as those that are prone to landslides or liquefaction.

As part of its advocacy on natural disaster preparedness, Phivolcs encouraged the public to begin educating children for them to develop a “culture of preparedness” on top of the annual shake drills being conducted across the country.

The earthquake

The epicenter of the magnitude 7.8 earthquake that happened in the afternoon of July 16, 1990 was placed in the town of Rizal in Nueva Ecija which hit nearby provinces of Pangasinan, La Union, Baguio City, and the rest of the Cordillera region, and even as far as Metro Manila, Calabarzon, and the Bicol region.

According to the Philippine Institute of Volcanology and Seismology (Phivolcs), the earthquake was triggered by the sudden movement of the northwest segment of the Philippine Fault Zone (PFZ) and of its north trending splay, the Digdig fault.

A 125 kilometer-long ground rupture along the Digdig segment that stretches from Dingalan, Aurora to Kayapa, Nueva Vizcaya was produced following the earthquake.

Effects and damages

Four regions in the north and central Luzon suffered the heavy damage and casualties with the cities of Baguio, Dagupan, Cabanatuan and San Jose bearing the brunt of the disaster.  

Ishmael Narag, officer-in-charge of the Seismological Observation and Earthquake Prediction Division of Phivolcs, said the 45-second extreme ground shaking caused multiple structural damages including the collapse of several buildings in Baguio City such as the Hyatt Terraces hotel, as well as roads and bridges in other provinces.

He added that a total of 1,283 people were killed by the strong impact of the earthquake, while 3,516 were injured, and 460 were missing. The cost of damage to property amounted to P99 billion.

Recovery and Rehabilitation

Narag admitted that the country was very young in terms of earthquake monitoring when the July 1990 earthquake occurred, and this came as a wake-up call for the government and other organizations to step up their disaster monitoring and preparedness capability.

Following the earthquake, Narag said a lot of agencies including those from the international level, expressed their willingness to help the country in the recovery and rehabilitation efforts, as well as in upgrading our response capability to natural disasters.

From the 12 earthquake monitoring stations network prior to the July 1990 event, the Phivolcs has increased this to 29 seismic stations by 1995 and began the construction of other stations as well as the hiring of field personnel and training of its staff. 

Currently, Phivolcs officer-in-charge director Renato Solidum Jr., said there are at least 104 monitoring stations in the country.

In 1996, then Phivolcs director Dr. Raymundo Punongbayan initiated the updating of the bureau’s earthquake intensity scale from a nine-point to a ten-point intensity scale.

From the year 2000 up to 2015, the Phivolcs continued to densify its network with the help from the government of Japan through improving its earthquake and volcano monitoring in the country.