PHILIPPINE Institute of Volcanology and Seismology (Phivolcs)-Northern Mindanao Director Marcial Labininay said the series of quakes that struck Mindanao was caused by a "very active" fault line in North Cotabato.
The said fault line is still active at present. Labininay reminded the public to be prepared as earthquakes are unpredictable.
For October alone, Mindanao was rocked by two strong earthquakes and several aftershocks.
The first occurred in the evening of October 16, with Phivolcs recording a magnitude 6.3 quake in Tulunan, North Cotabato. This was followed by several aftershocks.
This was followed by the magnitude 6.6 earthquake still in Tulunan, North Cotabato which caused several damages, deaths and injuries.
"Ang mga aftershocks ay maliit na magnitudes kaysa main shock. Kapag malaki yung magnitude, hindi sya related dun sa main shock," Labininay said.
Labininay further said there's no active fault line in Cagayan de Oro City.
However, there are three active fault lines in Misamis Oriental, namely: Central Mindanao Fault Line (from Gingoog City going to Malaybalay Bukidnon), cabanglasan Fault Line (from Balingasag, Misamis Oriental going to Malitbog, Bukidnon), and Tagoloan River Fault Line (from Villanueva, Misamis Oriental to Manolo Fortich, Bukidnon).
"Yung mga earthquake generators natin dito sa Mindanao, this time very active. So dapat maghanda tayo, be prepared, always be vigilant because walang makapag-predict ng incoming, approaching earthquake," Labininay said.