Fault system in S. Mindanao possibly to generate higher than M6 earthquake —PHIVOLCS

Marje Pelayo   •   December 17, 2019   •   1063

MANILA, Philippines – The Mindanao region has been experiencing strong ground shaking in the past months.

The most recent was a magnitude 6.9 earthquake on Sunday (December 15) which according to the Philippine Institute of Volcanology and Seismology (PHIVOLCS) was caused by the Tangbulan fault, a 69.2 kilometer stretch that traverses Davao del Sur to Davao Oriental.

According to PHIVOLCS OIC and S&T Undersecretary Renato Solidum, these movements can cause other faults in the region to move as well.

From 1908 to 1970, around five incidents of ground shaking with intensities no stronger than 5 to 8 were experienced across the Davao Region.

The agency noted Southern Mindanao as among the places in the country that sit on multiple fault systems.

The Tangbulan fault alone, the agency explained, can generate up to magnitude 7.2 earthquake.

Towards the east of Tangbulan fault is the Digos fault which can produce up to magnitude 6.3 tremor.

Towards the west is the Makilala-Malungon fault which can generate up to magnitude 7.2 earthquake and is connected to the Cotabato Fault system.

Near the Cotabato fault system lies other faults including the Makilala Fault, Balabag Fault, Matalam Fault, M’lang Fault, North Columbio Fault and the South Columbio Fault.

These faults also can cause ground shaking even stronger than magnitude 6.

The earthquake in October this year, PHIVOLCS noted, was caused by the Cotabato Fault System.

The agency is now closely monitoring the movements of these faults especially those which have been active in the past 10 years.

“Overall sa Mindanao, itong Cotabato-Davao del Sur area ay isa sa rehiyon na walang masyadong malakas na earthquake (Overall in Mindanao, this Cotabato-Davao del Sur stretch is one area in the region that produces small earthquakes),” Solidum said.

“Ibig sabihin may fault, naiipon ang energy, and at some point magbibigay ito, ipapakawala niya ang energy kung kumilos ang fault. So mga strong to major earthquakes ang kaya niya (This means, these faults are generating energy and at some point, it will eventually release this energy when the fault moves. That time, they can produce strong to major earthquakes),” the official added.

Aside from structural damages, PHIVOLCS also warns of possible landslide due to aftershocks or strong rains in mountainous areas where cracks are already visible because of the previous ground shaking. MNP (with details from Rey Pelayo)

Several evacuees in Batangas City evacuation center decide to stay despite clearance from LGU

Maris Federez   •   January 28, 2020

Evacuees in the 12 towns of Batangas have started to return to their homes after the Philippine Institute of Volcanology and Seismology (Phivolcs) lowered the alert level of the Taal Volcano from 4 to 3.

Several evacuees in Batangas City, however, opted to stay behind for fear of a major explosion of Taal.

Lilibeth Arajo, a resident from the town of Taal who is now in an evacuation in Batangas City, said they are still awaiting the final decision of the authorities to really be sure that it is indeed safe to go home.

She added that their house is on the outskirts of Taal and transportation is not easily accessible.

Another evacuee said it is not yet certain that there will be immediate livelihood or source of income for them should they go home now. — (with details from Vincent Arboleda) /mbmf

Thick, white steam from Taal means volcanic materials are rising — PHIVOLCS

Marje Pelayo   •   January 24, 2020

MANILA, Philippines — Taal Volcano spewed anew a tall column of thick, white steam early Friday morning (January 24).

Experts from the Philippine Institute of Volcanology and Seismology (PHIVOLCS) explained that the white steam-laden plumes of about 500 meters high that drifted towards the southwest direction signify that the heating up of volcanic materials underneath the crater has intensified.

In a press briefing, Volcano Monitoring Chief Ma. Antonia Bornas explained that the thick steam means that excessively hot volcanic materials are rising, causing the water to boil.

Mayroon po kasi tayo talagang magma na umaakyat at ito po talaga ang binabantayan natin (The magma is still moving up and this is what we are monitoring at present),” Bornas said.

Iyong steam ito po ay mula sa ground water or sa tubig ng lawa na sumisipsip sa ilalim ng lupa nung nagkaroon tayo ng fissuring at ito po ay nalilikha sa ibabaw ng magma dahil napakainit po nito at ibinubuga iyong steam (The thick steam came from ground water or the lake water that is drying up in the event of fissuring. There is evaporation going on top of the very hot magma thus steam is produced),” she added.

Bornas also noted the increase in sulfur dioxide (SO2) emission from 144 tons per day on Thursday (January 23) to an average of 224 tons per day on Friday.

Still, PHIVOLCS stressed that the high frequency of volcanic tremors indicates that the magma is continuously rising and may still result to an eruptive explosion.

Based on PHIVOLCS monitoring, Taal Volcano has generated 486 volcanic earthquakes including four low-frequency earthquakes.

The agency said Alert Level 4 still remains in effect over Taal Volcano which means a hazardous explosive eruption is possible within hours to days.

PHIVOLCS reiterates that forced evacuation of Taal Volcano island remains necessary as well as other identified high-risk areas where fissures are being observed.

Continuous tremors recorded, Taal Volcano still swollen — PHIVOLCS

Marje Pelayo   •   January 23, 2020

A handout photo made available by the Philippines’ Office of Civil Defense shows an aerial view of the Taal Volcano crater in Batangas province, south of Manila, Philippines 21 January 2020. The alert level of Taal Volcano remains at four following its eruption on 12 January, as authorities continue to implement measures to keep citizens from returning to their homes in danger zones around the volcano. EPA-EFE/OFFICE OF CIVIL DEFENSE

MANILA, Philippines – Activities in the main crater of Taal Volcano may have been weaker but the signs of rising magma are still visible, according to the latest report from the Philippine Institute of Volcanology and Seismology (PHIVOLCS).

Based on PHIVOLCS’ 8:00 AM advisory (January 23), Taal volcano has generated weak to moderate emissions of white steam about 50 to 500 meters high from the main crater.

Emissions of sulfur dioxide (SO2) was measured at an average of 141 tonnes/day.

For the past 24 hours, PHIVOLCS recorded 467 volcanic earthquakes at the Taal Volcano network which means such intense activity likely signifies continuous magmatic intrusion beneath the Taal edifice.

PHIVOLCS emphasized that such may lead to further eruptive activity.

Alert Level 4 still remains in effect over Taal Volcano, according to the agency, as hazardous explosive eruption is still possible within hours to days.

Volcano experts strongly reiterate total evacuation of Taal Volcano Island and high-risk areas as identified in the hazard maps.

This covered areas within the 14-km radius from the Taal main crater and along the Pansipit River Valley where fissuring has been observed.

PHIVOLCS is continually monitoring the eruption and vows to provide updates of further developments in Taal volcano region.

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