(Eagle News)–The series of earthquakes that hit Batangas on Wednesday, April 22, are volcano-tectonic in origin.
The Philippine Institute of Volcanology and Seismology said this means the 23 earthquakes that struck Mabini and adjacent areas of Balayan Bay since 10:30 a.m. were “associated with failure or breakage of rock material along faults and fractures beneath active volcanos.”
PHIVOLCS said although the root causes of tectonic earthquakes, which the Batangas quakes were initially described due to their occurrence within the locality of the April 8, 2017 6.0-magnitude Mabini earthquake, are similar, their root causes are different as purely tectonic quakes are “driven by regional tectonic plate motion.”
“(Volcanic-tectonic) earthquakes are normally triggered by excess heat or pressure from, or adjustment of the crust around, a magmatic body beneath the volcano,” PHIVOLCS explained.
PHIVOLCS clarified, however, that quakes classified as volcano-tectonic “should not be interpreted by default as being related to the renewal of magmatic unrest, rather day-to-day seismic activity in Taal volcano” as explained in the Taal volcano bulletins issued daily at 8 a.m.
The magnitudes of the earthquakes were also revised as being measured by a local magnitude through the Taal Volcano Network, which differs from the customary surface magnitude calculated by the Philippine Seismic Network.