Phivolcs explains why Pampanga was hit hardest by Luzon quake

Robie de Guzman   •   April 23, 2019   •   18531

MANILA, Philippines – The center of the magnitude 6.1 earthquake that rattled parts of Luzon on Monday was traced in Castillejos, Zambales, but the province of Pampanga recorded the hardest hit.

The Philippine Institute of Volcanology and Seismology (Phivolcs) explained that aside from being a neighbor of Zambales, the province sits on soft sediment and alluvial soil.

Alluvial, in geology, means made up of or found in the materials that are left by the water of rivers, floods among others. An area with softer soil is prone to strong shaking during an earthquake.

Although the temblor was not considered major, Phivolcs said, it was felt by many because it was a bit shallow.

Monday’s earthquake had a depth of 21 kilometers.

“Kaya nagkaroon ng damages sa Pampanga, bukod sa malapit siya sa episentro ng lindol ay malambot yung area na yan. Alluvial area po yung Pampanga kaya malakas yung shaking na mararamdaman,” said Phivolcs Senior Science Research Specialist Melchor Lasala.

(Pampanga recorded heavy damages because aside from being near the quake’s epicenter, the province has soft soil. It is an alluvial area so the shaking was amplified.)

Among the areas that suffered heavy damages were Porac, Angeles and Lubao.

The National Disaster Risk Reduction and Management Council (NDRRMC) on Tuesday reported 16 fatalities in the quake, 15 of which were from Pampanga.

Five people were killed in the collapse of a four-story supermarket in Porac, seven in different barangays in Porac, two in Lubao and one in Angeles.

READ: Luzon quake death toll rises to 16

The earthquake that struck Castillejos, Zambales on Monday was also felt in Metro Manila, parts of Bataan, Tarlac City, Batangas and Cavite.

Phivolcs said it has yet to identify if the recent quake in Luzon originated from an existing active fault in Zambales.

“Yung dalawang fault system na tinitingnan namin yung Iba Fault at East Zambales Fault,” Lasala said.

(We are looking at two fault systems, the Iba and East Zambales fault.)

Lasala added that the movement felt on Monday was called “strike slip”.

“‘Pag strike slip may dalawa tayong slab yung fault—yung left at yung right. Sa behavior, horizontal yung movement niya. ‘Yung isa papunta sa kaliwa yung isa sa papunta sa kanan,” Lasala explained.

Strike-slip faults are vertical (or nearly vertical) fractures where the blocks have mostly moved horizontally, according to the United States Geological Survey (USGS) earthquake glossary.

If the block opposite an observer looking across the fault moves to the right, the slip style is termed right lateral; if the block moves to the left, the motion is termed left lateral. 

Phivols also believes that the magnitude 6.1 quake that jolted Zambales will not trigger a movement of the West Valley Fault as it is 100 kilometers away from the epicenter traced in the Castillejos town.

According to a 2004 study, the West Valley Fault runs through the cities of Marikina, Pasig and Muntinlupa. It is capable of generating a magnitude 7.2 quake that could kill up to 34,000 people and injure 100,000 others. — Robie de Guzman (with details from Rey Pelayo)

Ilang bahagi ng Candaba, Pampanga lubog sa baha dahil kay ‘Rolly’

Robie de Guzman   •   November 2, 2020

MANILA, Philippines – Hindi na maaaring daanan ng mga sasakyan ang ilang kalsada sa bayan ng Candaba sa Pampanga dahil sa baha bunsod ng epekto ng bagyong Rolly.

Sa ulat ng Provincial Disaster Risk Reduction and Management Office (PDRRMO), umabot sa anim na talampakan ang lebel ng tubig sa Barangay San Agustin sa Candaba kaya hindi madaanan sa ngayon ng lahat ng uri ng sasakyan ang Candaba-Baliuag Road.

Hindi rin passable sa ngayon ang Candaba-San Miguel Road dahil sa baha na aabot sa tatlong talampakan.

Ang Bayu Road naman sa bayan ng Masantol sa lalawigan ay hindi rin maaaring daanan ng light vehicles.

Iniulat ring PDRRMO ang paglikas ng 1,150 pamilya o katumbas ng 4,431 indibiduwal dahil sa bagyo.

Ang mga residenteng ito ay mula sa mga bayan ng Sasmuan, Macabebe, San Luis, Lubao, Magalang, Masantol, Arayat, Porac at San Simon na pawang malapit sa high-risk coastal areas.

Nananatili ang mga ito sa mga evacuation center habang hindi pa ligtas balikan ang kanilang mga bahay.

Mahigpit rin ngayong binabantayan ang lebel ng tubig sa Pampanga River at mga bayang nakapalibot sa ilog.

“Kung makikita niyo ho ang command center natin, continus monitoring ho tayo sa bagyo natin, yung main river natin, especially Pampanga River, main rivers nation makikita niyo nandiyan lahat yan, nakamonitor po kami. So alam namin ang paltas ng tubig sa lahat ng mga river channel natin well monitored po ng command center natin,” ang wika ni Pampanga Governor Dennis Pineda.

Tiniyak naman ni Pineda na nakahanda ang puwersa ng lokal na pamahalaan para tumugon sa pangangailangan ng mga residenteng apektado ng bagyong Rolly.

“Lahat po ng mga social workers natin naka-in place na po diyan na pagdadalhan ng mga tao. Ready na po tayo, don’t worry,” ang pahayag ni Pineda.

“‘Yung health protocol po alam na ng mga tao natin, may face shield at face mask na rin po dun. Huwag po kayong matakot,” dagdag pa niya.

Nasa 10,000 relief packs rin ang nakahanda sa emergency operations center ng PDRRMO. Pati mga rescue equipment gaya ng rubber boats, loader at mga ambulansya ay inihanda na rin sakaling kailanganin ang pagsagip sa mga residente. – RRD (mula sa ulat ni Correspondent Leslie Huidem)

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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