The Philippine Institute of Volcanology and Seismology (Phivolcs) has detected five earthquakes that include one tectonic event and four low-frequency quakes and low-level background tremor at Taal Volcano in the past 24 hours.
In a volcano bulletin, Phivolcs said that the low-level background tremor lasted over 15 hours, from 1:45 p.m. on Tuesday, April 6 to 5:30 a.m. Wednesday, April 7.
Phivolcs also observed the "weak" emission of steam-laden plumes from Taal Volcano's vents that rose five meters.
Taal Volcano's sulfur dioxide emission averaged 1,454 tonnes per day on Tuesday, April 6 from 1,198 tonnes per day on Monday, April 5.
Meanwhile, temperature highs of 71.8 degrees Celsius and pH of 1.59 were last measured from the main crater lake on March 4 and Feb. 12, 2021, respectively.
Phivolcs added that ground deformation parameters continued to indicate a "very slow and steady inflation and expansion of the Taal region after the January 2020 eruption."
"These parameters may indicate increased magmatic activity at shallow depths beneath the edifice," it said.
Phivolcs pointed out that Taal Volcano will remain under Alert Level 2.
It has been Alert Level 2 since March 9, 2021.
"Sudden steam-driven or phreatic explosions, volcanic earthquakes, minor ashfall, and lethal accumulations or expulsions of volcanic gas can occur and threaten areas within and around TVI (Taal Volcano Island)," it pointed out.
It warned the public from entering the volcano island, which is a permanent danger zone, especially the vicinities of the main crater and Daang Kastila fissure.
Occupancy and boating on Taal Lake should also be strictly prohibited, Phivolcs added.
Local government units were advised to continuously assess and strengthen the preparedness of previously evacuated barangays around Taal Lake in case of renewed unrest.
Civil aviation authorities were also asked to advise pilots to avoid flying close to the volcano as airborne ash and ballistic fragments from explosions and wind-remobilized ash may pose hazards to aircraft.