The magnitude 7.4 earthquake that struck offshore of General Luna, Surigao del Norte, a few hours ago was generated by the Philippine Trench but is not related to the two strong tremors that occurred in Davao Del Norte last week, according to the state seismologist.
“Although both were generated by the Philippine Trench, the two earthquakes are unrelated,” Charmaine V. Villamil, Senior Science Research Specialist at the Philippine Institute of Volcanology and Seismology (PHIVOLCS), said in a Zoom interview in a mix of English and Tagalog.
“The trench is long, and the earthquakes happened in separate segments of the trench,” Ms. Villamil said.
According to PHIVOLCS, the Philippine Trench is a subduction zone located along the eastern coast of the country, extending over 1,300 kilometers in length and about 30 kilometers wide, stretching from Bicol to the Visayas and Mindanao.
Due to its length and being one of the six active trenches in the country, the trench is likely to generate subsequent, and sometimes strong, earthquakes, as is the case with the other active trenches, Ms. Villamil said.
Regarding various reports suggesting that recent earthquakes might trigger Metro Manila’s ‘Big One,’ Ms. Villamil said it will not, as the quake is expected to be caused by the West Valley Fault.
The fault stretches over 100 kilometers, passing through highly populated areas from Bulacan and parts of Metro Manila to Calamba in Laguna.
“Even with technology in other countries, they still cannot predict when an earthquake will occur. We should only rely on reliable sources like PHIVOLCS,” Ms. Villamil said.
PHIVOLCS said the fault experienced its last earthquake in 1658 and is now ripe for a strong and destructive quake, following its 200- to 400-year earthquake cycle.
If Metro Manila’s Big One occurs, it could reach a magnitude of 7.2 and produce an intensity of VIII, stronger than the quakes felt in Davao and Cebu.
Instead of being swayed into fear, Ms. Villamil said, preparation is king in the case of the Big One in Metro Manila, and it goes beyond just preparing a ‘Go Bag Kit’ and conducting earthquake drills.
“Preparation must be a way of life, as simple as identifying the obstacles in your house just in case of an earthquake,’ she said.
As the usual cause of death in earthquakes is falling debris, Ms. Villamil also reminded that houses and buildings must be structurally sound to withstand at least a magnitude 7.2 quake.
Also, PHIVOLCS reported that more than 113 aftershocks have been recorded following the Surigao del Norte quake, ranging from magnitude 1.2 to 4.4, as of 8:00 a.m. — Edg Adrian A. Eva