The Philippine Institute of Volcanology and Seismology (Phivolcs) monitored "localized" earthquake activity in Kanlaon Volcano in Negros Island since Tuesday evening, Feb. 8.

In an advisory, Phivolcs said 11 "very shallow" earthquakes between magnitudes 0.9 and 2.1 were recorded by the Kanlaon Volcano Network as of 9 a.m, Wednesday, Feb. 9.

"DOST-Phivolcs (Department of Science and Technology-Phivolcs) is currently monitoring localized earthquake activity on the lower northwest flank of Kanlaon Volcano, in the jurisdiction of Bago City, Negros Occidental, that began at 8:12 p.m. on Feb. 8, 2022, it said.

It added that ground deformation data from continuous GPS measurements indicate slight inflation of the middle to upper edifice since mid-October 2021, while short-term deflation since December 2021 and January 2022 was recorded by EDM and electronic tilt monitoring, respectively, on the southeastern flanks.

"Overall, localized shallow seismic activity and short-term ground deformation are likely caused by shallow hydrothermal or geothermal processes beneath the edifice that could generate phreatic or steam-driven explosions," Phivolcs said.

It reminded the public that Kanlaon Volcano remains under Alert Level 1, which means it continues to manifest low-level unrest.

"The local government units and the public are strongly reminded that entry into the four-kilometer radius permanent danger zone must be strictly prohibited due to the further possibilities of sudden and hazardous steam-driven or phreatic eruptions," Phivolcs said.

Furthermore, residents on the lower slopes of Kanlaon were advised to report any unusual observations to their local officials or to the Kanlaon Volcano Observatory at La Carlota City, Negros Occidental.

"Civil aviation authorities must also advise pilots to avoid flying close to the volcano’s summit as ejecta from any sudden phreatic eruption can be hazardous to aircraft," it added.