The Philippine Institute of Volcanology and Seismology (Phivolcs) detected a total of 58 earthquakes in Taal Volcano from Thursday, April 8 to Friday, April 9.
In a volcano bulletin issued on Friday, Phivolcs said of the 58 quakes recorded, 51 of these were episodes of volcanic tremors having durations of one to three minutes, one was a volcano-tectonic event, and six were low-frequency volcanic earthquakes.
Phivolcs said a low-level background tremor that started at 9:05 a.m. on Thursday is ongoing as of Friday morning.
It also observed a "weak" emission of steam-laden plumes from Taal Volcano's vents that rose five meters.
Taal Volcano's sulfur dioxide emission averaged 1,155 tonnes per day on Thursday, while, 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 since 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.