More than 3,000 weak and successive earthquakes were monitored in Southern Mindanao from 2025 to January this year, months before the magnitude 7.8 earthquake that struck the island on Monday, according to the Philippine Institute of Volcanology and Seismology (PHIVOLCS).
Study Released in May
The study, released on May 15, identifies the activity of the Cotabato Trench, an active submarine fault line in the region. According to PHIVOLCS science research, these successive tremors, or earthquake swarms, were recorded during that period, indicating that the trench remains active.
Reference to 1976 Moro Gulf Earthquake
The study also references the devastating 1976 Moro Gulf earthquake (Magnitude 8.1), considered one of the most destructive earthquakes in Philippine history.
PHIVOLCS clarified that the recorded earthquake swarm and the magnitude 7.8 earthquake did not originate from the same fault. According to them, different segments of the Cotabato Trench were the sources of the tremors.
Importance of Earthquake Swarms
Experts say that although an earthquake swarm is not a direct indication of a strong earthquake, it serves as an important reminder that the fault line is active and that residents should always be prepared for possible tremors.
