RESTIVE KANLAON: Early morning quakes jolt Negrenses

By Dolly Yasa

BACOLOD City – An early morning earthquake followed by a series of aftershocks jolted residents of Negros Occidental province including this city at around 1 a.m. Monday as Kanlaon volcano acts up again.

Successive posts about the quake appeared on social media in the aftermath of the magnitude 4.7 temblor.

Based on information provided by the Philippine Institute of Volcanology and Seismology (Phivolcs), the initial tremor was measured at magnitude 4.7 with a depth of 9 kilometers. Its epicenter was 16 kilometers east of La Carlota City.

The quake was felt at Intensity V in La Carlota City, Intensity III in Bacolod City, and Bago City; and Intensity II in Sipalay City.

A second tremor of the same magnitude struck at around 2:06 a.m. with the same epicenter.

Both tremors were tagged as “volcano-tectonic” in origin, according to Philvolcs.

Phivolcs said it is currently monitoring the ongoing series of earthquakes on the west lower flanks of Kanlaon Volcano.

The quakes began June 21, 2020 at 04:03 pm, with the strongest registered at magnitude 4.7 on June 22, 2020, 01:15 AM.

As of 8 am Monday, a total of 136 volcano-tectonic earthquakes were observed in just 24 hours, with the strongest recorded at magnitude 3.2 to 4.7.

PhilVolcs said four of these earthquakes at 1:01 am, 1:04 am, 1:34 am, and 2:06 am were recorded at magnitudes 3.2 to 4.7 by the Philippine Seismic Network and were felt at Intensities II to V in La Carlota and Bago City, Negros Occidental and Canlaon City, Negros Oriental.

Activity at the volcano’s vent consisted of moderate emission of white steam-laden plumes that rose 200 meters before drifting southwest. Sulfur dioxide (SO2) emission was measured at an average of 438 tonnes/day on 13 June 2020.

Ground deformation data from continuous GPS measurements indicate a slight deflation of the lower and mid slopes since January 2020.

Short-term electronic tilt monitoring on the southeastern flanks recorded continuing deflation on the lower slopes but inflation on the mid slopes since April 2020. These parameters indicate that hydrothermal or magmatic activity is occurring beneath the edifice.

Phivolcs reminded the public that Kanlaon Volcano is at Alert Level 1 which means that it is at an abnormal condition and has entered a period of unrest.

The local government units and the public are strongly reminded that entry into the 4-kilometer radius Permanent Danger Zone (PDZ) must be strictly prohibited due to the further possibilities of sudden and hazardous steam-driven or phreatic eruptions.

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.