While some active volcanoes in Luzon and the Visayas are showing restiveness, two earthquakes of tectonic origin yesterday struck Mindanao, the third and fourth earthquakes on the island this month. The Philippine Institute of Volcanology and Seismology (Phivolcs) said the first of the two temblors occurred at 3:16 a.m. yesterday, with the epicenter located 11 kilometers northwest of Surigao City in the northeastern tip of Mindanao. Seismologists said the earthquake, which registered at 3.7-magnitude, was traced to a movement along the Philippine Fault Zone (PFZ) East Mindanao Segment. Intensity 2 was felt in Surigao City.
The second temblor occurred yesterday at 1:27 p.m. which registered a 3.3-magnitude. The epicenter of the earthquake was located six kilometers southwest of Surigao City, where intensity 2 was felt in the area. The second temblor was also believed to have been caused by the movement along the PFZ — East Mindanao Segment. Last June 4, a 4.5-magnitude temblor also jolted Surigao del Sur, particularly Bislig town and Butuan City. Its epicenter was located at 34 kms southeast of Tandag, the capital of Surigao del Sur. Last June 11, a 2.3 magnitude quake struck Zamboanga del Sur’s Pagadian City, which was felt at intensity 1 in Zamboanga City.
The only temblor this month which occurred outside Mindanao was recorded last June 1 in Iba, Zambales. The two quakes yesterday is said to be the 56th and 57th recorded this year and the fourth and fifth temblor to be registered for this month. Meanwhile, after four steam and ash emissions this month, the Philippine Institute of Volcanology and Seismology (Phivolcs) has raised Kanlaon volcano’s alert level from zero to one. “Phivolcs is now raising the alert status of Kanlaon volcano from its repose (no alert) to Alert Level 1 to implement an initial stage of safety precautions,” it said.
Phivolcs said heightened alert on the volcano indicates that “all visits” within the volcano’s four kilometer Permanent Danger Zone (PDZ) are “suspended until further notice.” “Areas fronting gullies leading to the upper slopes should be avoided because lahar and rockfalls may affect these areas, especially during heavy rains on the volcano’s slopes,” the institute added. Phivolcs said Kanlaon volcano was “quiet” during the 24-hour observation period yesterday. However, it warned that Kanlaon’s low-level period of unrest could “intensify.” Last June 3 at about 2:30 p.m., the volcano showed its first steam/ash emission, described by seismologists as a “brief period of steam/ash emission.”