LEGAZPI CITY, Philippines—The Philippine Institute of Volcanology and Seismology (Phivolcs) detected 17 volcanic earthquakes on Friday around Mt. Bulusan in Sorsogon during the past 24-hour observation period.
Ed Laguerta, Phivolcs resident volcanologist here, said the rising number of quakes that rocked Mt. Bulusan for the past two observation periods since Thursday was of “no intensity and magnitude.”
Laguerta said the quakes “were only very small caused by fracturing cap rocks triggered by steam driven pressure which is an ordinary volcanic behavior of Bulusan.”
READ: Quakes jolt Mt. Bulusan
He also said there is no basis to raise the current alert level 1 over Mt. Bulusan.
Phivolcs raised alert level 1 on Sept. 16 over the volcano following an apparent increase in volcanic quakes around it.
Laguerta said despite the regular phreatic explosions, quakes and ground deformation, there are no new indicators yet for the agency to change Mt. Bulusan’s alert status.
“What we are looking for closely are the parameters that would show an increase in gas outputs, new ash chemistry containing pulverized magma and low frequency harmonic tremors,” he noted.
A Phivolcs bulletin released Friday also said Mt. Bulusan belched out 250 meters high steam plumes.
Laguerta dismissed speculation on the possibility of a twin eruption of Mt. Bulusan and Mt. Mayon in Albay. The two volcanoes are both in the same restive mode and were under alert level 1.
READ: Alert level 1 raised over Mayon but no imminent eruption expected
He said there is no scientific basis to assert that the volcanoes might erupt at the same time.
“There are no connectivity between the two volcanoes or other volcanoes in the country. They may be associated with the Philippine trench but they have different behaviors,” Laguerta said.
He cited that if the twin eruption happens it would be a “coincidence” but it is far-fetched since Mayon Volcano’s behavior is magma-driven while Bulusan eruptions are mainly due to steam or hydrothermal pressures.
On Thursday, Phivolcs also noted eight earthquakes around the volcano.
Alert level 1 (abnormal) remains in effect, as the public is reminded not to enter the 4-kilometer Permanent Danger Zone (PDZ) due to sudden phreatic eruption. RAM