A total of 383 earthquakes, which include 238 episodes of volcanic tremors that lasted one to 12 minutes, were recorded around Taal Volcano from Tuesday, April 13 to Wednesday, April 14.
Of the total quakes, the Philippine Institute of Volcanology and Seismology (Phivolcs), said 143 were low-frequency volcanic earthquakes and a low-level background tremor that began at 9:05 a.m., Thursday, April 8.
Phivolcs said the upwelling of hot volcanic fluids at Taal Volcano's main crater lake was observed on Tuesday morning, April 13.
A 300-meter steam-laden plume was also observed from active "fumaroles" or opening on the northern side of the volcano, it added.
Taal Volcano's sulfur dioxide emission averaged 1,886 tonnes per day on Monday, April 12, 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.
As of Wednesday, Phivolcs maintained the Alert Level over Taal Volcano at Alert Level 2.
The restive volcano in Batangas has been under 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)," Phivolcs 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.