The Philippine Institute of Volcanology and Seismology (Phivolcs) maintained Alert Level 3 for Taal Volcano on Thursday, January 30, pronouncing that magma is still moving underneath.
In a hearing of the Senate committee on urban planning, housing, and resettlement, Phivolcs Director Renato Solidum Jr explained they recorded a harmonic tremor associated with magma movement on Thursday.
The harmonic tremor, according to Solidum, is a sign that there is still rising magma coming from Taal. He noted the additionally recorded earthquakes beyond the 24-hour period.
Phivolcs, in its 8 am bulletin on Thursday, said the Taal Volcano Network recorded 137 volcanic earthquakes in 24 hours, compared to the previous record of 123. The harmonic tremor, according to Solidum, lasted for 97 seconds. Two low-frequency events were also recorded.
According to the US Geological Survey, low-frequency quakes are "as a result of cracks resonating as magma and gases move towards the surface.
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Meanwhile, the Philippine Seismic Network has plotted 763 volcanic earthquakes as of January 12, 1 pm. Of these, 177 have been magnitudes 1.2 to 4.1 and have been felt at Intensities I to V.
Philippine Seismic Network additionally plotted seven volcanic earthquakes from 5 am on Wednesday, January 29 until 5 am on Thursday, at magnitudes 1.7 to 2.5 with no felt event.
Phivolcs had reduced Taal's status to Alert Level 3 from Alert Level 4 on January 26. The volcanic activity could either ease more - leading to Alert Level 2 - or increase again - a possible return to Alert Level 4.
The experts based the alert degree based on the volcanic activity, explained Solidum. The officials, according to Solidum, hoped that there would be a continuous downward trend of the parameters they see to lower the alert level.
Solidum continued that around 30 million cubic meters out of 80 million cubic meters had been released from January 12 to 13, the first two days of the volcanic unrest.
The magma "is absolutely parked" approximately five kilometers beneath the crater, according to Solidum. He added the agency is still monitoring whether the magma would be pushed upward or not.
Phivolcs additionally observed "weak emission of white to dirty white steam-weighted down plumes 300 to 500 meters tall" coming from Taal's most important crater in the past 24 hours.
The level of sulfur dioxide (SO2) emitted, according to Phivolcs, was "too low" to be detected.
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Seven barangays in Batangas, including the Taal Volcano Island, remain on lockdown. These regions are inside a 7-kilometer radius from the main crater, which is Phivolcs' recommended hazard zone.
Taal's eruption displaced thousands of families living either on the island or on nearby adjacent lakeshore towns.
Solidum said the decision is up to the local government units, whether they would allow residents to return to their homes. The official said Phivolcs is just in charge of providing the data on the volcano's movements, Solidum said.