Agusan Fault Likely Source of Recent Mindanao Earthquake
BUTUAN CITY (MindaNews / 28 December) – The Philippine Institute of Volcanology and Seismology (Phivolcs) has identified the Philippine Fault-Agusan Marsh segment as the likely source of the earthquake that struck Talacogon, Agusan del Sur on December 26.
According to a brief report published on Friday, the magnitude 5.3 earthquake, with a depth of 12 km, showed strike-slip faulting, or horizontal motion, along the fault. The Philippine Fault-Agusan Marsh segment was identified as the likely source.
Earthquake Tremors and Aftershocks
The earthquake triggered aftershocks, including a magnitude 4.6 quake with a depth of 7 km. Phivolcs emphasized the significance of the Philippine Fault-Agusan Marsh segment within the larger Philippine Fault system that runs through Agusan del Sur. Earthquakes along this segment can impact neighboring provinces, highlighting the importance of preparedness across the region.
Intensity of the Earthquake Across Mindanao
Phivolcs published an updated earthquake bulletin reporting the earthquake was felt in a large part of Mindanao.
- Intensity V was recorded in Talacogon.
- Intensity IV was observed in Bislig City and Hinatuan in Surigao del Sur.
- Intensity III was felt in the City of Gingoog, Jasaan, Magsaysay, and Medina in Misamis Oriental; Laak, Mabini, Monkayo, and Nabunturan in Davao de Oro; and Barobo in Surigao del Sur.
- Intensity II was reported in Malitbog and Valencia City in Bukidnon; Claveria, Tagoloan, and Villanueva in Misamis Oriental; Cagayan de Oro City; Maco in Davao de Oro; Kabacan and Matalam in Cotabato; and Cagwait in Surigao del Sur.
Preparedness and Ongoing Research
Phivolcs acknowledges that predicting earthquake timing and magnitude is impossible. However, they emphasize that approaching these risks with caution and readiness is crucial. Earlier this year, Phivolcs published a study “Stress Releases and Seismic Gaps: Earthquake Sequences Strike Eastern Mindanao, Philippines” which highlighted increasing tectonic stress along the Philippine Fault in Mindanao, possibly influenced by recent earthquakes along the Philippine Trench. The study also pointed out historical seismic gaps, particularly in the Esperanza, Agusan Marsh, and Mati segments of the Philippine Fault, raising concerns about future earthquakes.
“These findings reinforce the importance of disaster preparedness and encourage communities to prioritize proactive safety measures in their daily lives,” the study said.
In Mindanao, the Philippine Fault consists of several segments, including Surigao, Esperanza, Agusan Marsh, West Compostela Valley, Central Compostela Valley, Nabunturan, East Compostela Valley, Caraga River, Mati, and Lianga. (Ivy Marie Mangadlao/MindaNews)
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