Occurrence of volcanic earthquakes main parameter in determining alert level in Taal — PHIVOLCS

The occurrence of volcanic earthquakes is the principal parameter in raising or lowering the alert levels over active volcanoes in the Philippines such as Taal Volcano, according to PHIVOLCS on Wednesday.

Taal Volcano's unrest can only be declared as slowing down when "earthquakes have diminished and the trend is continuing," PHIVOLCS Director Renato Solidum said in an interview on ANC television.

Alert Level 4, indicating a possible hazardous eruption within hours to days, is currently raised over the said volcano in the southern part of Luzon. Thousands of residents have already been evacuated amid possible base surge and volcanic tsunami once the big eruption takes place.

"If you look back at all the recorded earthquakes after the 1 p.m. initiation  of Taal (on Sunday), we have recorded  more than three thousand," Solidum said.

"But in terms of plotting or locating—because not all earthquakes are big, some of these are small it's very difficult to locate—466 earthquakes are already plotted and 156 of these were reportedly felt," he added.

According to PHIVOLCS, the intense seismic activity at Taal Volcano "probably signifies continuous magmatic intrusion beneath the Taal edifice, which may lead to further eruptive activity." — Dona Magsino/RSJ, GMA News