115 quakes recorded at Taal volcano in 24 hours

MANILA, Philippines— (UPDATE) Taal Volcano was rocked by 115 earthquakes in the past 24 hours, the highest number of tremors recorded in the area since the Philippine Institute of Volcanology and Seismology placed the restive volcano under Alert Level 2 last April.

It was the highest number in a day, a jump from the average of 10 mild quakes daily since alert level 2 (increasing restiveness) was hoisted over Taal on April 9, said Jaime Sincioco, officer-in-charge of the Volcano Monitoring and Eruption Prediction Division of Phivolcs, in a phone interview.

He said that in the series of the 115 volcanic quakes recorded up to 3 a.m. Monday, 12 were of intensity 1 to 4 and “were felt by the residents” on the volcano island.

The strongest quake, also since April 9, was felt at intensity 4 at around 1:05 a.m.

Phivolcs said residents around the volcano in Taal, Batangas heard rumbling sounds and felt up to Intensity IV earthquakes but no physical changes were left on the ground, Sincioco said.

Julio Sabit, head of the volcano monitoring division, said the earthquakes were an indication that Taal will continue to be restive.

Phivolcs’ bulletin said the volcano’s increased seismic activities and sustained high emission rate of carbon dioxide being released in its main crater lake meant that magma has been intruding towards the surface.

It advised the public that the main crater, the Daang Kastila Trail, and Mt. Tabaro on the island remained off-limits to everybody.

In a Radyo Inquirer interview, Sabit said that the quakes were “part of its on-going activity, if you would notice, its already on Alert level 2, meaning… there is a confirmed rising of magma from below, so these tremors are part of the episodic rising of magma.”

“Taal volcano has experienced earthquake swarms long before, ever since the 90’s, but it has not erupted.”

Sabit also added that “The volcano’s activity varies because previously the quakes were scattered in several areas but the recent ones were clustered in one area.”

Asked whether the recent fish kill incident in Sampaloc Lake was connected to the quakes, Sabit said that “the fish kill occurred in one area, if volcanic activity caused it, it should have affected the area near the volcano first. San Pablo City, Laguna is quite far from the Taal volcano.”

Sabit said that the fish were probably killed because of the sudden change in temperature.

Although the number of quakes recorded last Sunday was a “remarkable” increase from the previous day—there were only 10 volcanic quakes observed on May 29—Sabit said Phivolcs would still not upgrade to 3 the alert level on the volcano. Sincioco said Phivolcs said that monitoring will continue in the coming days.

“If this (high number of volcanic quakes) is sustained, it could eventually lead to an eruption,” he said.

Allan Loza, resident volcanologist at the Taal Observatory based in Talisay, Batangas, said the increased number of volcanic quakes should not cause panic, but residents should be “doubly cautious.”

Sincioco said that as what had happened sometime in 1994, numerous volcanic quakes “reaching over a thousand” were also recorded over Taal but did not culminate in an eruption.

Island residents, meanwhile, refused to evacuate from their homes despite the increased volcanic activity, said Talisay mayor Zanaida Mendoza.

Taal volcano has had 33 eruptions since 1572, the latest was on October 3, 1977. Its major eruptions happened in 1965 to 1970 and in 1976 to 1977.

Taal volcano in Batangas province is about 400 kilometers by land from Mayon volcano in Albay and about 470 kms from Bulusan in Sorsogon. Mayon and Bulusan volcanoes are both under an alert level 1 (low-level unrest.

Roemart Tamayo, Inquirer.net

Originally posted at 3:36 pm | Monday, May 30th, 2011