Two strong tectonic earthquakes struck Southern Leyte and Zamboanga del Norte hours apart on Thursday morning, sending students out of classrooms as well as damaging roads, homes, and other infrastructure.
The Philippine Institute of Volcanology and Seismology (Phivolcs) recorded a magnitude-5.8 tremor in San Francisco, Southern Leyte at 7:39 am. It was estimated at 11 kilometers deep and affected many areas across Visayas and Mindanao.
The United States Geological Survey (USGS) said it had a depth of 25 kilometers and left cracks on buildings and houses, according to an Agence France Presse (AFP) report. San Francisco town rescuer Roxanne Sandoval said there were no immediate reports of casualties.
“It was a strong shake that lasted up to one minute,” Sandoval told AFP. “I thought it was just a strong wind, but then I felt the ground and it was as if it was spinning.” A team was deployed to check the severity of damage to roads and houses reported by residents.
Phivolcs said it expected damage from this tremor as well as aftershocks. As of 6:00 pm on Thursday, state seismologists already recorded 90 aftershocks (28 plotted) from this seismic event with magnitudes ranging from 1.5 to 2.9.
“The earthquake is associated with the movement of a local active fault in the area,” Phivolcs said in a primer. It described Southern Leyte and its neighboring provinces as “seismically active” in the region, noting that aftershocks from the latest quake could “persist for several days to months.”
Another strong quake in Siocon, Zamboanga del Norte was also reported at 11:41 am. It was initially measured at magnitude 6.1, but was later downgraded to 5.4 as updates came in—consistent with the reading of USGS.
Based on the latest Phivolcs bulletin, Intensity 5 was reported in the quake’s epicenter as well as Zamboanga City, Ipil in Zamboanga Sibugay, and the City of Isabela. It was also felt at Intensity 4 in the towns of Sibuco, Dimataling, and Alicia across the Zamboanga peninsula.
The tremor also affected Dipolog City, President Manuel A. Roxas, Buug and Siay as well parts of Antique, Negros Occidental, Negros Oriental and Maguindanao in lesser intensities. Phivolcs monitored at least three aftershocks from this tremor measuring 1.0 to 2.2 in magnitudes.
Quakes are a daily occurrence in the Philippines, which sits along the Pacific “Ring of Fire,” an arc of intense seismic and volcanic activity that stretches from Japan through Southeast Asia and across the Pacific basin.
Most are too weak to be felt by humans, but strong and destructive quakes come at random with no technology available to predict when and where they will happen.
On Wednesday evening, a strong earthquake also shook parts of Surigao del Norte. The tremor was measured at magnitude-4.5 and located 14 kilometers southeast of General Luna at 23 kilometers deep. No casualties have so far been reported from these seismic events. —With Agence France Presse