Why do we need to understand the Big One? Phivolcs explains

Published November 25, 2021, 5:15 PM

by Manila Bulletin

The Big One is defined as a “strong and damaging” earthquake scenario.

(File Photo / Phivolcs)

As explained by the Philippine Institute of Volcanology and Seismology (Phivolcs), this is also often equated to the worst-case earthquake that may happen in the Greater Metro Manila Area.

However, the agency reiterated that they provide many worst-case and localized earthquake scenarios.

“Therefore, there can be many Big Ones,” it added.

As part of its talk series during the National Science and Technology Week, Phivolcs on Thursday, Nov. 25, held an online discussion in understanding the earthquake scenarios in the Philippines.

“Kailangang malaman natin na ‘yung Big One ay hindi lamang nasa Metro Manila (We need to understand that Big One is not only possible in Metro Manila),” said Phivolcs’ Supervising Science and Research Specialist Jeffrey Perez.

“Maaari [rin] magkaroon ng Big One sa bawat region, bawat probinsya, at bawat siyudad sa buong Pilipinas (It can also occur in every region, every province, and every city in the Philippines),” he added.

PH as a ‘seismically active’ country

Phivolcs reported that an average of 20 earthquakes are recorded in the Philippines per day with at least 100 to 150 quakes being felt per year.

Additionally, the agency said that the country endured about 100 destructive earthquakes for the past 400 years.

Phivolcs explained that earthquakes occur in the Philippines because it is part of the Pacific Ring of Fire.

Due to its geographic and tectonic location, the country also has many sources of earthquakes which are divided into two categories: trenches and active faults.

Earthquake scenarios

Phivolcs said that earthquake scenarios are assumed hazard scenarios describing the estimated ground shaking (intensity), potential hazards, and impacts that can be caused by a specific earthquake.

“An effective scenario is realistic, bound with science-based facts and close to reality; specific, with specific location and time constrained if possible; and locally-relevant, having a role to the disaster-preparedness of the public,” the agency said.

Phivolcs also disclosed that they generate earthquake scenarios by identifying the maximum credible earthquake based on a fault length, by considering the local soil conditions, by studying the recurrence interval of a quake, and through seismic hazard scenarios and extent of impacts modeled using simulations and fragility curves.

Importance of preparing for a worst-case earthquake scenario

Knowing the worst-case scenario of an earthquake may help one to lessen the impact of the disaster, Phivolcs said.

If given enough data, the agency said that the country may determine specific impacts to a locality.

Aside from that, local government units will be able to determine the appropriate strategies for mitigation, preparedness, response, and coordination.

“When distinctive impacts are explained, individuals and communities can understand that disasters can be prevented and mitigated,” Phivolcs added. (Charie Mae F. Abarca)