4 new fault zones discovered in Luzon

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July 4, 2026 | 12:00am

MANILA, Philippines — Researchers have discovered four new fault zones beneath the sea west of Luzon, according to a study conducted by the University of the Philippines.

The faults appeared to be branching out from the main Philippine Fault Zone (PFZ),  the study, released by the UP office of the vice president for academic affairs, said.

Experts from UP Diliman and Taiwan authored the research.

The PFZ is a major fault system linked to earthquakes and crustal movement across the country. 

Researchers said that understanding how the PFZ works is essential for earthquake risk reduction. 

The study noted that the full extent of the PFZ, especially where it ends in northwest Luzon, remains unclear. 

“We used advanced imaging tools including high-resolution seafloor maps and seismic profiles to get a clearer picture of what lies offshore,” the authors said. 

One of the faults’ branch appears to extend the main fault to the Manila Trench, a major undersea feature where earthquakes and tsunamis can also originate.

The researchers said the fault may even be splitting the trench into two parts. 

“What makes this more intriguing is that the Manila Trench bends sharply as it moves southward by about 35 degrees. This matches with the direction of the Pacific Fault Zone. Below this area, seismic data showed that the Earth’s crust is torn at deeper levels,” the authors said. 

The study showed that in the north, one part of the tectonic plate is dipping gently downward, while it dips more steeply in the south.

Researchers said the tearing may be caused by two major geologic collisions happening at the same time – one from the Palawan Microcontinental Block pushing from the southwest, and another from the Philippine Rise pushing from the northeast.

“Why does this matter? These newly mapped faults and the tearing of the Earth’s crust can help explain how and where large earthquakes may happen in the future,” the authors said.

By identifying these geologic structures, one can better understand the complex forces shaping Luzon and improve hazard assessments and earthquake preparedness, they added.