By Ma. Cristina Arayata | Philippine News Agency
Taal Volcano continues to release high seismic energy, and a sudden phreatic or phreatomagmatic eruption could occur at any time, the Philippine Institute of Volcanology and Seismology (Phivolcs) warned on Monday.
For the past 24 hours, five volcanic tremors that lasted for a total of 450 minutes were recorded in Taal.
In an interview with the Philippine News Agency, Phivolcs Director Teresito Bacolcol said these tremors contribute to the high seismic energy release amid 19 volcanic earthquakes in Taal Volcano last Sunday.
Increased seismic energy refers to the total amount of seismic energy released, which can be measured by RSAM (real-time seismic amplitude measurement). RSAM, he said, is a measure of the total seismic energy of ground vibrations at a volcano.
Seismic energy is the energy released by the Earth during geological processes from the sudden movement or fracturing of rocks underground, caused by built-up stress along faults or by magma movement beneath a volcano.
Although the total of 19 seems few, Bacolcol noted that the RSAM increases if the high-energy and continuous tremors are detected.
“RSAM can be described as the volcano’s ‘heartbeat monitor’. If the activity is normal, the heartbeat trace is low and steady. When high-energy volcanic tremor occurs, the ‘heart beat’ becomes faster and stronger. As a result, the RSAM rises,” he said.
Bacolcol also clarified that an increase in seismic energy is different from increased seismicity, which refers to the increase in the number of earthquakes recorded.
Thus, the “pronounced increase” that Phivolcs used in its advisory last Sunday referred to the seismic energy release as measured by the RSAM, and not the number of volcanic earthquakes.
“If there is a sudden increase in RSAM and there is an occurence of volcanic tremor, this may indicate that hot fluids (which could be gases or magma) are flowing and possibly interacting with ground water,” Bacolcol said.
This interaction could result in a sudden phreatic or phreatomagmatic eruption.
Bacolcol said that such a possibility also happened just last month.
On July 6, the Phivolcs released an advisory because of the increase in RSAM.
Eleven days later, on July 17, there was a phreatomagmatic eruption with a plume height of 2,400 meters, he said.
Meanwhile, Taal Volcano is still under Alert Level 1. Residents should remain alert, and local government units should be vigilant, Bacolcol said.
He added that entry into the permanent danger zone, which covers the whole of Taal Volcano Island, should be strictly prohibited. (PNA)
