In earthquake studies, the 'finders keepers' idiom does not hold

When earthquakes strike, they sometimes leave a trace on the ground called a surface rupture, which is a manifestation of the fault that generated the tremor. This happens when the energy released at the earthquake source, called the focus, is strong enough to break the ground at the surface. 

A surface rupture is thus mainly a function of the magnitude (energy released) and the depth of focus of the earthquake. The stronger the magnitude and the shallower the focus, the more likely a surface rupture will form. Not all earthquakes, even at large magnitudes, produce a surface rupture.

The magnitude 6.9 earthquake of September 30, 2025, with a shallow depth of focus of around 5 kilometers, produced a surface rupture first discovered by geologists of the Philippine Institute of Volcanology and Seismology in the village of Nailon near the northern shore of Bogo City in northern Cebu island.

KINGSTON, JAMAICA, 5 March 2025 — Dr. Mario Aurelio, the first Filipino elected to the Legal and Technical Commission (LTC) of the International Seabed Authority (ISA), participated in the first part of the 30th ISA Session, at the ISA headquarters in Kingston, Jamaica, from 03 to 14 March, 2025. 

On August 18, 2020 at the height of the COVID-19  pandemic, Masbate Island in the central Philippines was struck by a magnitude 6.6 earthquake whose epicenter was located in the southern coastal town of Cataingan. This tremor killed at least one individual and levelled off a building near the epicenter. Seventeen years earlier, on February 15, 2003 a magnitude 6.3 tremor struck the same island. The epicenter was located less than forty kilometers to the northwest of the 2020 earthquake, in the town of Uson. 

While no one wishes for earthquakes, without them it would be impossible to understand these phenomena and would continue to threaten an unprepared society with their attendant hazards.

The recent decision of the Philippine government, through its Department of Environment and Natural Resources (DENR), to rescind its contract with the developer of the Masungi Georeserve in Tanay, Rizal, could put an important geological effort of confirming the inland presence of Paleocene rocks in the Philippines in jeopardy.

Whichever party emerges victorious in this legal battle, the Masungi Limestone as a geological formation must be protected by way of a robust conservation and preservation program. 

July 16, 2024 was the 34th anniversary of an earthquake that devastated major cities in northern Luzon. This earthquake was so powerful that it sent seismic waves that were felt as far as Metro Manila, located more than a hundred kilometers from the epicenter.

On the afternoon of July 16, 1990, a Monday, a magnitude 7.8 earthquake struck northern Luzon with an epicenter located near the town of Rizal in the province of Nueva Ecija. More than 1,500 individuals perished while infrastructure damage was estimated at more than 12 billion Philippine pesos (>USD 200 million).