WATCH: Phivolcs explains ‘earthquake swarm’ in Batangas

Voltaire Tupaz
WATCH: Phivolcs explains ‘earthquake swarm’ in Batangas
Director Renato Solidum Jr of the Philippine Institute of Volcanology and Seismology corrects the false reports circulating online

BATANGAS CITY, Philippines – On Monday, April 10, Science Undersecretary Renato Solidum Jr corrected a number of online posts about the twin earthquakes that rocked Batangas on Saturday. He visited the provincial capital to explain the science behind the earthquakes to local officials and employees.

Solidum, who is the concurrent director of the Philippine Institute of Volcanology and Seismology (Phivolcs), described the tremors as an “earthquake swarm” or “a series of quakes without a distinct or significantly large earthquake.” 

It was triggered by an unnamed fault in the Mabini area, he said, noting that “there have been minor quakes in the area in the past.”

“The fault has no surface manifestation. It’s moving gradually. It’s better that way – that it moves slowly – because it would be more destructive if it moves abruptly,” Solidum told Rappler in an interview.

According to Phivolcs, a magnitude 5.6 quake first struck at 3:07 pm, off Mabini, Batangas. The first quake was then followed by a magnitude 6.0 tremor at 3:09 pm, also in the same area.

As of April 9, 9:00 pm, the number of earthquakes triggered by the fault reached around 2,000. Most of these were small, and they could neither be located precisely nor felt, Solidum said. 

The fault is not a major one. It is only short, traversing an area that used to be a volcano that is still hot. When the fault moves, it does not trigger a strong earthquake because the area is not hard.

Facts behind the Batangas quakes 

Solidum also corrected wrong reports circulating online that have caused panic in areas hit by the eathquakes. He has clarified earlier that a tsunami is not expected to occur after the quake.

In an interview with Rappler, he emphasized on the following facts about the Batangas earthquakes:

  • The fault will not trigger a volcanic eruption

At present, the fault will not trigger any volcanic eruption because it did not cause a strong earthquake. If it will have an effect on a volcanic activity, the public would know if the volcano is responding to an earthquake. A volcano could erupt regardless of a fault.

  • The fault has nothing to do with the West Valley Fault

The fault that is moving along the Mabini area is not connected to the West Valley Fault. (READ: How close are you to the West Valley Fault? Here’s a site for that)

So what happened there does not affect the 100-kilometer West Valley Fault that traverses parts of Bulacan through Metro Manila – from San Mateo in Rizal in the north, to Quezon City, Marikina, Pasig, Makati, Taguig, and to Parañaque in the south; San Pedro, Biñan, Sta Rosa, Cabuyao, and Calamba in Laguna; and Carmona, General Mariano Alvarez, and Silang in Cavite. 

  • Earthquakes cannot be predicted 

Currently, no one has the capacity to determine when an earthquake will strike, at what precise magnitude, and where the next strong one will hit. The reason for this is that there are many faults, and faults do not show consistent signs of activity.

What is the role of Phivolcs?

Solidum stressed Phivolcs does not predict earthquakes but conducts hazards analyses and assessments, and makes this information available to the public.

The agency collaborates with other government agencies in mitigating the damaging effects of earthquakes. It operates and maintains a network of 92 seismic stations spread across the Philippines. Data from the seismic stations are used to determine the location, magnitude, and other characteristics of the earthquakes generated.

“Please do not believe messages stating prediction of events. And do not forward any of these. Official information would only come from official addresses (Facebook and Twitter) or sites of Phivolcs,” Solidum urged the public.

Earthquake observations may also be reported to the agency at telephone numbers (02) 929-9254 and (02) 426-1468 to 79, local numbers 124 and 125.

Solidum added that the public can also rely on news media because they get information from official sources. –

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