Batangas aftershocks easing but continuing swarm still possible

By , on April 11, 2017


The seismic swarm or series of small to moderate earthquakes rocking Batangas province may persist throughout this Holy Week and beyond. (Photo: Taal, Batangas/Facebook)
The seismic swarm or series of small to moderate earthquakes rocking Batangas province may persist throughout this Holy Week and beyond. (Photo: Taal, Batangas/Facebook)

MANILA—The seismic swarm or series of small to moderate earthquakes rocking Batangas province may persist throughout this Holy Week and beyond.

Philippine Institute of Volcanology and Seismology (Phivolcs) has not discounted yet such possibility, noting that Batangas may still experience in forthcoming days earthquakes that are actually aftershocks of the magnitude 6.0 earthquake that struck Mabini municipality there last week.

“Some of those aftershocks may even be felt but people must remain calm,” said Phivolcs science research analyst Bhenz Rodriguez.

He urged owners concerned to have their structures checked if they sustained damages from the earthquake.

“A weak aftershock may either further damage such structures or even cause these to collapse,” he noted.

Rodriguez said latest data indicated some decreasing frequency of aftershocks from the Mabini earthquake.

“Aftershocks from that earthquake may still occur in forthcoming days, however,” he said.

He noted although aftershocks’ frequency decreases over time, it’s difficult to say when the swarm in Batangas will end.

According to experts, aftershocks are earthquakes resulting from a main shock or earthquake that’s larger in magnitude than these seismic events.

Rodriguez said aftershocks of last week’s magnitude 6.0 earthquake in Batangas were part of the seismic swarm plaguing this province.

The magnitude 5.5 earthquake in Batangas’ Tingloy municipality last Tuesday (April 4) and its aftershocks were also part of such swarm, he noted.

From being a main shock, Phivolcs reclassified the Tingloy earthquake as a foreshock due to occurrence of the magnitude 6.0 earthquake in nearby Mabini this Saturday (April 8).

Phivolcs also reclassified the Tingloy earthquake’s aftershocks as foreshocks since these occurred before the Mabini earthquake struck, said the agency’s science research analyst Tom Simborio.

Foreshocks are earthquakes that precede larger magnitude main shocks or earthquakes in the same location, noted experts.

Citing latest available data as of 8 a.m. Tuesday (April 11), Phivolcs data management specialist Jay Gallardo said 1,353 aftershocks of the Mabini earthquake already occurred.

Fifteen of such aftershocks were felt, he noted.

He noted the Mabini earthquake also had some 1,000 foreshocks.

“Those foreshocks and aftershocks comprise the swarm happening in Batangas at present,” said Simborio.