Fault system in S. Mindanao possibly to generate higher than M6 earthquake —PHIVOLCS
Marje Pelayo • December 17, 2019 • 1215
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)
MANILA, Philippines – The Philippine Institute of Volcanology and Seismology (Phivolcs) on Friday downgraded Taal Volcano’s status from alert level 3 to alert level 2 following indications of decreased unrest in the recent weeks.
In its bulletin, Phivolcs said it lowered the alert level status of Taal Volcano after three weeks due to less frequent volcanic activity, stabilizing ground deformation of the Taal Caldera and Taal Volcano Island edifices, and weak steam or gas emissions at the Main crater.
“DOST-PHIVOLCS is lowering the alert status of Taal Volcano from Alert Level 3 to Alert Level 2 to reflect the overall decreasing trend in the level of monitoring parameters,” it said.
Alert Level 2 means there is decreased unrest, but State volcanologists said this should not be interpreted that unrest has ceased or that the threat of an eruption has disappeared.
The agency also reminds the public that at alert level 2, sudden steam-driven or phreatic explosions, volcanic earthquakes, ashfall and lethal accumulations or expulsions of volcanic gas can occur and threaten areas within the volcano island and its coast.
It also advised that entry to the Taal Volcano Island – a permanent danger zone – shall remain prohibited.
“Local government units are advised to additionally assess previously evacuated areas within the seven-kilometer radius for damages and road accessibilities and to strengthen preparedness, contingency and communication measures in case of renewed unrest,” Phivolcs said.
“People are also advised to observe precautions due to ground displacement across fissures, frequent ashfall, and minor earthquakes. Communities beside active river channels particularly where ash from the main eruption phase has been thickly deposited should increase vigilance when there is heavy and prolonged rainfall since the ash can be washed away and form lahars along the channels,” it added.
Civil aviation authorities are also advised to direct pilots to avoid flying close to the volcano as airborne ash and ballistic fragments from sudden explosions and wind-remobilized ash may pose hazards to aircraft.
Phivolcs said alert level 3 may be raised again should an uptrend or pronounced change in monitored parameters forewarn a potential eruption.
On January 12, Taal Volcano spewed kilometers-high ash plumes which prompted state volcanologists to raise its status to alert level 4. Thousands of residents within the 14-kilometer radius from the main crater were ordered to flee their homes due to a possible hazardous eruption.
Two weeks later, Phivolcs downgraded Taal’s status to alert level 3, which allowed displaced residents outside the seven-kilometer danger zone to return to their homes.
MANILA, Philippines – The Philippine Institute of Volcanology and Seismology (PHIVOLCS) has observed the waning volcanic activities in Taal Volcano.
Although volcanic earthquakes can still be felt around Taal, they are less frequent and less intense according to DOST Undersecretary and PHIVOLCS-OIC, Renato Solidum.
Sulfur dioxide level has also been low in the past days, Solidum said.
“Sa 101 earthquakes, may 4 na low frequency earthquake events. Ito yung paggalaw ng magma o hindi kaya ay pagkilos ng gas, (Of the 101 earthquakes, only four were low frequency earthquake events. These could be the movement of magma or emissions of gases),” he said,
“Ito ay nangangahulugang mayroon pang magma activity sa paligid ng Taal volcano (This means there is still magma activity around Taal Volcano),” he added.
PHIVOLCS, likewise, is considering the trend of ground deformation or “swelling” of the volcano in its decision to downgrade alert level over Taal which remained at Alert Level 3 since January 26.
“Ang aming alam ay nagsa-subside na siya kung ito ay magpatuloy ay baka mai-consider na natin na magbaba tayo ng alert level, (Based on what we observed, (activities) have subsided and if this development continues, we may consider lowering our alert level),” Solidum said.
Solidum clarified, however, that Taal Volcano Island will remain a permanent danger zone even after they downgrade the danger status to Alert Level 2.
To date, residents are still barred from returning to houses within the 7-km radius as risk of explosion remains high.
Meanwhile, those who were allowed to return home are advised to check their structures and do the necessary repairs as occasional ground shaking poses threat of collapse or more serious damage. – MNP (with reports from Rey Pelayo)
MANILA, Philippines – Volcano authority DOST-PHIVOLCS has called on the public to help protect government instruments and immediately report the culprits who stole two solar panels from the agency’s Mount Mayon monitoring station.
The Volcano Monitoring Rest House (VMRH) hosts instruments for earthquake monitoring, Global Positioning System (GPS) and tiltmeter.
The stolen instruments, two solar panels of 150 watts each, were used to generate power supply for the station.
Without power supply, no data will be transmitted from this station and consequently will affect the monitoring of Mayon Volcano.
The incident was discovered by Mayon Volcano Observatory personnel during their routine inspection and preventive maintenance service on Wednesday (February 5).
Under Republic Act 10344 or the Risk Reduction and Preparedness Equipment Protection Act of 2012, “the unauthorized taking, stealing, keeping or tampering of government risk reduction and preparedness equipment, accessories and similar facilities” incurs corresponding penalty.
“The public is strongly encouraged to help in taking care of our monitoring instruments and to promptly report any untoward incidents,” the agency said.
Information on the stolen equipment and other concerns may be forwarded to DOST Undersecretary and PHIVOLCS OIC Renato Solidum Jr. at (+632) 8-426-1468 to 79.
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