In the Know: Areas within 14KM permanent danger zone and 20KM extended danger zone

Maris Federez   •   January 16, 2020   •   6887

MANILA, Philippines — Authorities have been appealing to the public not to enter the areas considered to be within the 14-kilometer and 20-kilometer danger zones surrounding the Taal Volcano.

The Philippine Institute of Volcanology and Seismology (Phivolcs) noted that Taal Volcano has caused more than 500 tremors since its phreatic explosion last Sunday.

Phivolcs added that the fissures seen on the ground near the volcano; the drying up of the lake and the swelling of the volcanic crater, are signs of an imminent major explosive eruption.

The alert level 4 is still raised over Taal Volcano which prompted authorities to enforce the 14-kilometer permanent danger zone and the 20-kilometer extended danger zone.

Local governments within these zones must implement total evacuation.

Areas within the 14-kilometer-radius danger zone include the towns of Agoncillo, San Nicolas, Talisay, Balete, and Mataas na Kahoy; parts of Lemery, Laurel, Tagaytay City, Tanauan City, and Cuenca; and some barangays in the towns of Taal, Sta. Teresita, Alitagtag, San Jose, Lipa City, and Malvar.

To date, several towns in Batangas, such as Agoncillo, San Nicolas, Talisay, Taal, and Laurel are locked down.

Meanwhile, areas within the 20-kilometer-radius extended danger zone include Tagaytay City, Tanauan City, Malvar, Alitagtag, Sta. Teresita, Taal, Lemery, and Mendez; parts of Indang, Alfonso, Amadeo, and Silang in Cavite; as well as Calamba City in Laguna, Sto. Tomas, Malvar, Lipa City, San Jose, San Pascual, Bauan, San Luis, Calaca, Balayan, and Nasugbu in Batangas.

Based on the hazard map issued by Phivolcs, a base surge might happen following a major eruption.

Phivolcs said the intensity of the heat from the steam and ash brought about by the base surge will cause the temperature to rise to up to 1,000˚Celsius.

The areas that may be affected by the base surge include the towns of Talisay, San Nicolas, Laurel, Agoncillo, Lemery, Taal, Sta. Teresita, and Tanauan City; as well as some parts of Alitagtag, Cuenca, Mataas na Kahoy, Balete and Lipa City.

On the other hand, the ballistic projectile or areas that can be reached by rocks or boulders that Taal Volcano might spew in case of a major explosion include the towns of Talisay, San Nicolas, Agoncillo, and Lemery.

The explosion could also cause a tsunami in the lake which might affect the surrounding communities.

Authorities appealed to the public for cooperation and to refrain from going back to restricted areas until the volcanic activities have subsided. — (from the report of Bernard Dadis) /mbmf

Phivolcs warns of possible lahar flow as Typhoon Ulysses looms over Luzon

Robie de Guzman   •   November 11, 2020

MANILA, Philippines – The Philippine Institute of Volcanology and Seismology (Phivolcs) on Wednesday warned of possible lahar streamflows in rivers and drainage areas on Pinatubo, Mayon and Taal volcanoes as Typhoon Ulysses creeps closer to Luzon.

In an advisory, Phivolcs said heavy to intense rainfall affecting Metro Manila, and portions of CALABARZON and Central Luzon due to Ulysses could generate volcanic sediment flows or lahars and muddy run-off in areas surrounding the said volcanoes.

The agency also said that prolonged and intense rainfall may generate non-eruption lahars on major rivers draining western Pinatubo Volcano where significant deposits of its last explosion in 1991 remain on the watershed.

“Pinatubo lahars are likely be channel-confined and occur on the upper to middle reaches of the Sto. Tomas-Marella and Bucao River systems but may transition to muddy streamflows and floods on the lower reaches and affect adjacent communities of San Marcelino, San Narciso, San Felipe and Botolan, Zambales Province,” Phivolcs said.

“Muddy streamflows may likewise be generated along the O’Donnell and Pasig-Potrero River systems draining the Pinatubo edifice to the north and southeast, respectively and affect downstream communities in Tarlac and Pampanga Provinces,” it added.

Continuous and heavy rains may also wash away loose rocks or soft soil surrounding Taal volcano, particularly on the slopes west of Taal Lake, “where thin remnant ash can be remobilized in streams and roads and overland of the lakeward slopes.”

Phivolcs said the lahar flow can recur particularly on previously affected communities of Agoncillo and Laurel, Batangas Province.

In a separate advisory, the agency also warned that rains brought by the typhoon could wash away loose material from thick pyroclastic density current deposits in Mayon Volcano from its last eruption in 2018.  

The bulk of erodible deposits currently occupy the watershed areas of the Anoling, Miisi, Binaan, Mabinit, Buyuan, Lidong and Basud Channels.

“Mayon lahars can threaten communities along the middle and lower slopes and downstream of these channels with inundation, burial and wash away,” Philvocs said.

“All the above channels are currently choked with sediment, gravel and boulders brought down by lahars generated by Typhoons “Quinta” and “Rolly,” resulting in shallowed and shifting potential lahar paths with increased risk to already impacted communities as well as those adjacent to these,” it added.

Phivolcs advised the communities and local government units in identified areas of risk to continually monitor the storm conditions and take pre-emptive response measures for their safety from Typhoon Ulysses.

The agency also strongly recommends increased vigilance and readiness of communities in pre-determined zones of lahar and related hazards on these volcanoes.

Phivolcs sees geohazard, flooding risks in Bulacan Airport

Aileen Cerrudo   •   September 25, 2020

The project site of the proposed New Manila International Airport in Bulacan has geohazard risks, according to the Philippine Institute of Volcanology and Seismology (Phivolcs).

The multi-billion airport is sitting on soft ground and its location is prone to frequent flooding, according to Phivolcs Usec. Renato Solidum.

“Just to be very specific on the facts is that it is far away from the fault. But since it’s underlain by sand with a shallow water table, it’s prone to strong ground shaking and liquefaction,” he said.

Solidum said they conducted an assessment to ensure the safety of the community as well as to protect investments. He recommended making buildings and infrastructure resilient to hazards.

“Dapat iyong building mo ay maayos ang disenyo na maging stable siya habang lumilindol at hindi siya tumagilid. Or pwede mo ring patibayan ang lupa. Bawasan mo iyong tubig, palitan mo iyong lupa, (The building should have a proper design for it to be stable during earthquakes. The ground can also be strengthen by reducing its water content or replacing the soil),” he added.

Meanwhile, San Miguel Holdings Corporation (SMC) said they have been taking into account the risks in designing the P740 billion domestic and international airport in Bulacan. The SMC also assured they have studied the project, including its feasibility, and all possible risks.

“The airport’s design fully takes this into account and we have actually started implementing sustainable measures to address flooding in Bulacan that has existed for several decades and has been made worse by clogged waterways and drainages,” according to SMC.

The corporation also tapped three major global airport construction firms to ensure the airport is resilient, sustainable, and will provide the best benefits for all Filipinos. AAC (with reports from Vincent Arboleda)

Magnitude 6.4 rocks Davao Occidental

Maris Federez   •   September 7, 2020

A magnitude 6.4 earthquake shook Davao Occidental at around 11:23 in the evening of Sunday, Sept. 6.

The Philippine Institute of Volcanology and Seismology (Phivolcs) said the tremor was located east of Don Marcelino in Davao Occidental with a depth of 149 kilometers.

The quake was tectonic in origin.

Phivolcs is yet to report initial damage, although it warned of aftershocks in the affected areas. —/mbmf

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