LEGAZPI CITY, Philippines—Volcanic quakes, sustained inflation of the edifice, gas emissions and crater glows are very important signs of a coming eruption of Mayon Volcano and people around it should never trust its momentary lull, this was the warning from Philippine Institute of Volcanology and Seismology (Phivolcs) director Renato Solidum Monday.

The Phivolcs has already installed two units of digital tilt meters along Mayon Volcano, particularly at Barangay Anoling in Camalig and at the Mayon Resthouse in Tabaco City, both within the six-kilometer permanent danger zone, Solidum said.

A tiltmeter is used in measuring ground deflation on the slopes of Mayon.

“As much as the scientists are keeping their eyes and ears on Mayon, no one should trust it on a daily basis of its manifestations but instead be very careful because the sustained threat is still there although we also refer to its 2006 eruption event (a protracted one),” he added.

Solidum explained that if magma was fast moving upwards towards the crater, it would explode violently like what happened in 1814 when the old Cagsawa town was buried in mud, rendering the area in ruins and another eruption recorded in 1897 with several thousands killed.

“Now, the rise and fall in the gas emission and earthquake rates indicate that Mayon is degassing and has time to release pressure and would wait for another fresh batch of magma push upwards, that is why there are changes in the rates of the monitored parameters,” he explained.

Solidum, however, warned that they could not say when or what kind of eruption (violent or not) but disaster authorities must maintain the warning against venturing at the six-kilometer permanent danger zone and the seven-km extended danger zone, especially at the southeast quadrant facing Daraga and Santo Domingo towns and this city.

“There is a need for a strong collaboration among local disaster councils to maintain the safety of the people and consistently attain a zero-casualty rate even in the event of its eruption,” he advised.

Mayon's trend of volcanic quakes showed a descending pattern in the past few days: 35 volcanic earthquakes were detected by the seismic network during the 6:01 a.m. Friday to 6 a.m. Saturday observation period; 23 volcanic earthquakes during the 6:01 a.m. Saturday to 6 a.m. Sunday period; and five volcanic earthquakes during the 6:01 a.m. Sunday to 6 a.m. Monday observation period.

As earlier warned by resident volcanologist Eduardo Laguerta, the continuous presence of tremors might already indicate a coming eruption.

Friday's bulletin revealed that harmonic tremors were continuously recorded from 8:36 a.m. Thursday until Friday.

“However, it was not consistently observed during the following observation period,” Laguerta said.