PHOTO COURTESY OF SHIELA TAN
LUCENA CITY — At least 12 volcanic earthquakes in Taal Volcano in Batangas province were detected over the last 24 hours, the Philippine Institute of Volcanology and Seismology (Phivolcs) reported on Friday morning, Sept. 20.
On Thursday, the earthquakes were accompanied by eight volcanic tremors, Phivolcs said in its bulletin.
On Wednesday, the volcano recorded three volcanic earthquakes and one tremor lasting two minutes.
READ: ‘Vog’ reappears after Taal Volcano emits voluminous sulfur dioxide
Phivolcs defines volcanic earthquakes as those “generated by magmatic processes or magma-related processes beneath or near an active volcano.”
“Unlike tectonic earthquakes that are produced by faulting, volcanic earthquakes are directly produced by many processes and are therefore much more varied in characteristics,” the agency explained.
Volcanic tremors, on the other hand, are “continuous seismic signals with regular or irregular oscillations and low frequencies (typically 0.5–5 Hz) that can last for more than a minute.”
The Phivolcs added: “Tremor can be caused by different processes inside the volcano, including resonance triggered by magma or magmatic gas flowing through cracks and vents, successive overlapping low-frequency earthquakes, and eruptions of magma.”
In its latest update, Phivolcs also recorded the emission of 8,223 metric tons (MT) of sulfur dioxide (SO2) from Taal’s main crater, which rose 1,200 meters high before drifting in a north-northeast direction.
An “upwelling of hot volcanic fluids in the Main Crater Lake” was also observed on Taal Volcano Island, locally known as “Pulo,” which sits in the middle of Taal Lake.
The Phivolcs reported the absence of “vog,” or volcanic smog, during the latest observation period.
Taal Volcano is still under alert level 1 (low level of volcanic unrest), Phivolcs said.
The agency reminded the public that Taal Volcano remained in an
“abnormal condition” and “should not be interpreted to have ceased unrest nor ceased the threat of eruptive activity.” INQ