BACOLOD CITY, Philippines—The Philippine Institute of Volcanology and Seismology (Phivolcs) has been closely monitoring the Negros trench following five earthquakes, the strongest one at a 5.2-magnitude, that hit Negros Occidental.
Ishmael Narag, Phivolcs Seismology Division officer-in-charge, said Monday afternoon that the 24-hour watch started when the last tremor hit at 10:10 a.m.
The epicenter of the earthquakes was offshore and believed to have been caused by sudden movements along the earthquake-generating Negros Trench, Narag said.
“We believe a subduction occurred where heavier denser plates dove into the interior of the earth, triggering five earthquakes recorded in Cauayan town and Bago City in Negros Occidental,” Narag said.
A subduction occurs when two oceanic plates collide, with the younger plate riding over the older one, according to Plate Tectonics website https://www.platetectonics.com/book/page_12.asp.
Narag explained that as a precaution, they were monitoring the Negros Trench although the magnitude of the tremors that occurred later Monday had gone down.
“These are small magnitude events that did not lead to any damage. But we are not discounting the possibility of having stronger earthquakes,” Phivolcs Director Renato Solidum also said.
The first quake was recorded at 12:24 a.m., with a magnitude of 3.6 in Bago City, followed by four others that hit Cauayan at 5.2-magnitude at 12:43 a.m., 4.8-magnitude at 1:40 a.m., 2.8-magnitude at 5:40 a.m. and 3.5-magnitude at 10:10 a.m., Phivolcs reported.
Cauayan Mayor John Rey Tabujara said they felt the earthquakes shake their town one after the other but these did not cause any damage nor was anybody harmed.