Phivolcs explains why Pampanga was hit hardest by Luzon quake
Robie de Guzman • April 23, 2019 • 17251
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.
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)
Pampanga Governor Dennis Pineda warned of reverting the province to enhanced community quarantine (ECQ) if the number of coronavirus disease (COVID-19) cases continues to rise.
“Tumaas po ang mga kaso natin. I have no choice kung hindi ibalik sa GCQ ito o ECQ kung aabot tayo sa worst situation (Cases in our province increased. I have no choice but to revert to GCQor ECQ if the situation worsens),” he said.
After the province was placed under modified general community quarantine (MGCQ) on June 15, new COVID-19 cases went up by 25. As of July 7, according to the Provincial Epidemiology and Surveillance Unit, there are 166 confirmed COVID-19 cases in the Pampanga, with 100 recoveries and 16 deaths.
Only Arayat and Masantol, Pampanga remain COVID-19-free, the Pampanga governor said. He reminds residents to only leave the house if necessary.
“Hindi po sinasabi ng MGCQ na libre kayo na makipagkwentuhan sa ibang lugar (Just because it’s MGCQ, it doesn’t mean you are free to meet up in other places),” he said.
Barangay Capalangan and Sulipan in Apalit are currently under hard lockdown until July 16 due to the surge of COVID-19 cases in the area. AAC (with reports from Leslie Huidem)
MANILA, Philippines — Mount Kanlaon in Negros Island is one of the most active volcanoes in the country similar to Mt. Pinatubo in Zambales, Mt. Mayon in Albay, Mt. Bulusan in Sorsogon, and Mt. Hibok-Hibok in Camiguin Island.
Based on the observation of the Philippine Institute of Volcanology and Seismology (PHIVOLCS), the volcano has recorded abnormal activities especially last Sunday (June 21) and Monday (June 22).
Earthquakes have been felt as the volcano spewed ashes.
Department of Science and Technology (DOST) Undersecretary and PHIVOLCS OIC Renato Solidum explained these activities may be attributed to an existing fault.
They are now observing if the tremors will move under the summit.
“Itong pagkilos ng fault ay posibleng sanhi dahil sa pag pressurize ng lugar sa Kanlaon volcano ng hydrothermal fluids o pagpapakulo ng tubig o di kaya ay mas malalim pang magmatic activity,” Solidum noted.
Most of the Kanlaon’s explosions were phreatic, the agency observed.
Based on studies of rock samples from the volcano, its last lava episode was in the early 1900’s.
In the 1996 eruption, three persons who went up the volcano died.
Usec. Solidum said Mt. Kanlaon is not comparable with the Taal Volcano when it comes to activities, though a major eruption is possible.
Alert Level 1 has been raised over Mt Kanlaon since March this year.
“Kung ang tanong mo ay mabilis yung escalation, wala tayong nakikitang ganung history sa Kanlaon based on record history (We didn’t have any record of rapid escalation based on Kanlaon’s record in history),” Solidum said.
“Pero yung posibilidad ng magkaroon ng mas malakas na eruption ay nandoon katulad ng Mayon Volcano; not Taal Volcano, hindi naman sila pareho ng setting (But there is the possibility of a major eruption like with Mount Mayon, but unlike Taal Volcano. Their settings are different),” he added.
PHIVOLCS warned that entering the four-kilometer permanent danger zone is strictly prohibited. MNP (with reports from Rey Pelayo)
Inihahanda na ng pamahalaan ng La Carlota City sa Negros Occidental ang disaster management plan na ipatutupad sakaling lumala ang ipinakikitang abnormalidad ng Mount Kanlaon.
Ayon kay La Carlota City Mayor Rex Jalando-on, nakapaloob sa kanilang plano ang pagtukoy sa mga barangay na lubos na maapektuhan at kailangang ilikas sakaling sumabog ang bulkan o kaya ay mas tumindi pa ang nararanasang pagyanig sa paligid ng bulkan.
Nakapaloob rin sa disaster management plan ang gagamiting logistics, transportation at available resources, pati na ang positioning ng food packs at mga lugar na maaaring gamiting temporary shelter ng mga ililikas na residente.
Tiniyak rin ni Jalando-on na mayroong P10 milyong quick response fund na maaaring gamitin ang lokal na pamahalaan.
Nagsasagawa na rin sila ng kampanya upang paalalahanan ang mga residente na maghanda at maging alerto sa gitna ng nararanasang pagyanig sa kanilang lungsod.
May gagawin ring drill upang malaman ng mga residente ang mga dapat gawin kapag nakaranas ng malakas na lindol o kaya ay sumabog ang bulkan.
Bahagya ring humina ang inilalabas na puting usok ng bulkan na umabot sa taas na 300 metro.
Iniulat rin ng PHIVOLCS ang patuloy na deflation sa ibabang bahagi ng bulkan at inflation o paglobo naman sa gitnang dalisdis na nangangahulugan umano ng hydrothermal o magmatic activity sa ilalim ng lupa.
Muli ring nagpa-alala ang ahensiya na nasa alert level 1 ang Mount Kanlaon na ang ibig sabihin ay nagpapakita ito ng abnormal na aktibidad at nasa “period of unrest.”
Naka-deklarang permanent danger zone ang four-kilometer radius ng bulkan at ipinagbabawal ang pagpasok rito ng mga tao.
Sakop naman ng eight-kilometer radius ng bulkan ang mga Barangay ng Ara-ala at Yubo kaya’t mahigpit itong binabantayan ng lokal na pamahalaan. – RRD (mula sa ulat ni Correspondent Lalaine Moreno)
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