A powerful earthquake with a magnitude of 5.9 hit near Lubang, Occidental Mindoro at 4:23 p.m. Tuesday, December 5, 2023./Inquirer Photo
MANILA, Philippines — The earthquake with a magnitude of 5.9 that occurred near Lubang, Occidental Mindoro on Tuesday is not a prelude to the “big one.”
Philippine Institute of Volcanology and Seismology (Phivolcs) Director Teresito Bacolcol said on Wednesday that the temblor that shook some parts of Luzon around 4:23 p.m. on Tuesday was caused by movements in the Manila Trench.
READ: Look Through: What happens when the ‘Big One’ hits Metro Manila?
Phivolcs explains why this is so
“Hindi po ito prelude to the ‘Big One.’ Again, ‘yung ‘Big One’ po natin would be generated to the West Valley Fault, and it has nothing to do with the trenches,” Bacolcol said over a Radyo 360 interview. (This is not a prelude to the “Big One”; again, our “Big One” would be generated to the West Valley Fault, and it has nothing to do with the trenches.)
“Huwag po sila mangamba kasi ‘yung nangyaring pag-lindol kahapon is nasa Manila Trench po and ‘yung the ‘Big One’ would be generated by the West Valley Fault. Magka-ibang fault sources po iyan,” he explained. (The public should not be afraid because yesterday’s earthquake was in the Manila Trench and the “Big One” would be generated by the West Valley Fault. Those are different fault sources.)
READ: EXPLAINER: Earthquake terms you need to know
Fault vs trench
Bacolcol also clarified the differences between a fault and a trench.
“‘Yung fault po, mga bato po iyan na either nagbabanggaan, nag-uumpugan, [naghi]hiwalay, or slide against each other. ‘Yung trench naman po, involve po dito ‘yung tectonic plates. So ‘yung tectonic plates po natin gumagalaw,” he explained. (Fault is when rocks either crash, collide, separate, or slide against each other. As for the trench, the tectonic plates are involved here. So our tectonic plates are moving.)
He also stressed that the 5.9-magnitude quake did not create any impact on the West Valley Fault.
READ: 5.9 magnitude quake strikes near Lubang, Occidental Mindoro
Manila Trench, West Valley Fault
“Wala pong epekto yan sa West Valley Fault dahil magkalayo po iyan [Manila Trench at West Valley Fault], magkaka-iba po ‘yung source. Nasa dagat po ‘yung Manila Trench and ‘yung West Valley Fault po nasa lupa,” he said. (That has no effect on the West Valley Fault because the Manila Trench and West Valley Fault are far apart; the sources are different. The Manila Trench is in the sea and the West Valley Fault is on land.)
However, Bacolcol still reminded the public to remain vigilant, especially since the “Big One” is estimated to happen around the year 2058.
READ: EXPLAINER: The series of earthquakes in Mindanao, and why Cebu can feel the tremors
The West Valley Fault last generated an earthquake in 1658, with an estimated recurrence interval of every 400 to 600 years.
“Reference lang po natin ‘yung 2058 but it could be earlier or later or it could be on the 600 upper limit,” he said. (The year 2058 is just a reference, but it could be earlier or later or it could be on the 600 upper limit.)