Philippine Institute of Volcanology & Seismology (PHIVOLCS) Anatomy of an Earthquake

When the Earth moves and the ground shakes, the tendency is often toward fear and panic. People forget what to do and run every which way. But there is more to learn about the normalcy of earthquakes, and the key toward facing this phenomenon is risk reduction and preparation. As the lead agency for this, the Philippine Institute of Volcanology and Seismology (PHIVOLCS) aims to understand these events in order to enlighten the public regarding these natural phenomena.

Established in 1982, PHIVOLCS is the primary agency concerned with volcanic eruption, earthquake and tsunami activity, and other geotectonic phenomena. It is a service institute under the Department of Science and Technology (DOST) mandated to ensure disaster preparedness and mitigate catastrophes resulting from volcanic eruptions, earthquakes, and tsunamis.

Dr. Renato U. Solidum, the Officer- in-Charge of PHIVOLCS, has 35 years of experience with the agency. He also serves as the DOST Undersecretary (Usec.) for Disaster Risk Reduction and Climate Change, where he works to supervise both PHIVOLCS and the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAG- ASA). “The goal is to make sure that both PHIVOLCS and PAGASA are able to provide the public with the best service by having improved systems, integrated projects, and support from other government agencies. It is also our role to operationalize and transfer
the technology that can be used by local government units (LGUs) and other sectors of society,” he says.

MAPPING OF FAULTS
Last April 22, 2019, the province of Zambales was rocked by a 6.1 magnitude earthquake, which was also strongly felt in Metro Manila..

“When the earthquake occurred, when the [geologic] fault moved beneath the mountains,
it released energy. That energy travelled and that was what we felt as intensity,” Dr. Solidum explains.

As one tectonic plate passes over another, they slip and bump against each other allowing energy to build up. When the plates move again, this energy is released along the Earth’s crust as seismic waves. The point on the surface where this occurs is called the epicenter. The measure of seismic energy released from the source of an earthquake is called the magnitude, measured by the Richter magnitude scale. It measures the strength or “size” of an earthquake. On the other hand, the severity of the shaking caused by an earthquake, with particular regard to property and human destruction, is called the intensity. Thus, for the 6.1 magnitude earthquake with the epicenter in Zambales last April 22, 2019, the intensity in Manila was around 4 to 5. In areas nearer the epicenter, the intensity was around 6 to 7 with many structures damaged in the neighboring province of Pampanga.