The earthquakes that have been rattling Batangas province since last week were spawned by an unnamed fault, a research specialist of the Philippine Institute of Volcanology and Seismology (PHIVOLCS) said Sunday.
"Iba ito sa West Valley Fault. May nakikita tayong fault dito sa lugar ng Mabini peninsula na gumagalaw. Sa ngayon wala pang specific na pangalan yung nasabing fault," Erlinton Olevere, PHIVOLCS science and research specialist, said in a radio dzBB interview.
He said the still unnamed fault runs along the Mabini peninsula, which had no history of any strong tremors.
Last Tuesday night, a magnitude-5.5 quake struck Batangas and nearby provinces. It was traced near Tingloy island.
On Saturday afternoon, two strong quakes struck Mabini town. The first significant quake was measured at 5.6 magnitude followed by a 6.0 tremor.
Both quakes were felt at Intensity 7 in Mabini town, where local authorities have reported severe damage to buildings, including schools and hospitals.
Based on the PHIVOLCS' Earthquake Intensity Scale, Intensity 7 is "destructive."
"Most people are frightened and run outdoors. People find it difficult to stand in upper floors. Heavy objects and furniture overturn or topple. Big church bells may ring. Old or poorly-built structures suffer considerably damage. Some well-built structures are slightly damaged. Some cracks may appear on dikes, fish ponds, road surface, or concrete hollow block walls. Limited liquefaction, lateral spreading and landslides are observed. Trees are shaken strongly," it said.
Olevere said in the interview that the two quakes on Saturday afternoon were aftershocks of last Tuesday night's event.
He said a total of 129 aftershocks have been recorded since Tuesday night.
Olevere also said in the interview that the unnamed fault will still have no surface manifestation, unlike those found following the Bohol and Surigao earthquakes, making it hard to pinpoint the exact location of the fault line.
"Kumbaga kung pupuntahan yung lugar ngayon wala ka pang makikitang biyak. Walang surface manifestation 'di kagaya sa Bohol na makikita natin na pagbiyak o yung sa Surigao na recent lang, nakita natin ang pagbitak ng lupa," he said.
"Dito wala pa namang nakikita so mahirap i-pinpoint pero base sa instrumento, dun bumabagsak karamihan yung aftershock [sa Mabini] so ibig sabihin nandyan yung kumikilos na fault," he added.
In a press conference, PHIVOLCS Director Renato Solidum clarified that there are no new faults along the Mabini peninsula. —Joseph Tristan Roxas/ALG, GMA News