14/10/2025
TQ Sci-Tech: The Clock Beneath Our Feet
by: Santine Mauritius Susa
Copyedited by: Joebbie Gaugano
Publication by:Rianne Lopez and Yelena Fabricate
The earth does not roar without a reason.
Last week, a series of powerful tremors off Davao Oriental jolted the Philippines awake—literally and figuratively. Within hours, twin major quakes struck the same offshore zone along the Philippine Trench, shaking cities from Mindanao to Visayas. Tsunami alerts blared and spilled into neighboring nations, aftershocks rippled through the region, and a nation accustomed to shaking was once again reminded of its uneasy balance on the Pacific’s fiery edge.
Scientists call this a “doublet earthquake,” —two major quakes that strike close together in both space and time. Instead of a single rupture and a slow fade of aftershocks, a doublet signals that one fault’s slip may have triggered another nearby. The Philippine Sea Plate, constantly diving beneath the archipelago, carries immense tectonic pressure. When one portion breaks, stress shifts to its neighbors, sometimes setting off a rapid cascade. That’s why this recent cluster of quakes—from Cebu in September to Davao in October—had scientists pay attention. Clustering doesn’t mean the ground is “angry,” but it does reflect how interconnected the Philippines’ faults truly are.
Earthquakes rarely occur in isolation. When one section of a fault releases energy, nearby areas may suddenly be closer to their breaking point. In a country crisscrossed by multiple faults, this domino effect can stretch over weeks or months. The Davao doublet is one example: a large quake may be followed not just by aftershocks but by related quakes within the same tectonic system. Similar clustering has been recorded in Japan, Chile, and Indonesia. In 2011, Japan’s devastating Tōhoku earthquake was followed by dozens of strong shocks along adjacent faults over the next year. In Chile, a 2010 quake triggered several magnitude 6+ tremors within months as stress redistributed along the South American subduction zone. These examples show that once one part of the earth’s crust gives way, others nearby can quickly follow.
Could such a cluster happen in Manila? Experts say yes, though in a different form. The capital sits atop the Valley Fault System, a network running beneath Quezon City, Marikina, Pasig, and Taguig. Unlike deep-sea quakes, this fault can trigger shallow, violent shaking that threatens dense urban areas. A magnitude 7.2 rupture along the West Valley Fault, which the Philippine Institute of Volcanology and Seismology (PHIVOLCS) has long warned about, could cause widespread damage—collapsing older buildings, splitting roads, and knocking out power and water lines across the metro. In this kind of inland cluster, one strong event could be followed by several smaller quakes in nearby fault segments, prolonging damage and panic.
Off the western coast also lies the Manila Trench—a deep subduction zone capable of generating powerful offshore quakes above magnitude 8 and large tsunamis. Scientists note that while it is less active than the Philippine Trench, its potential impact is far greater because it faces the highly populated coasts of Luzon. A major slip along the trench could send tsunami waves toward coastal towns in Zambales, Bataan, and even the Manila Bay area within minutes. In a worst-case scenario, residents might only have 15 to 30 minutes to move to higher ground. Historical records suggest that events like this may have occurred centuries ago, their traces buried in old coastal sediments now being studied by geologists.
Science provides warning, but preparedness ensures survival. Strengthening monitoring systems, enforcing building codes, and conducting regular drills remains as the country’s best defense. Earthquake-resistant design should be seen not as a cost but as a safeguard. Public awareness, meanwhile, turns panic into reflex—knowing where to go and what to do the moment the ground moves can save lives.
The Philippines cannot escape its geography, but it can adapt to it. Clusters like those in Mindanao remind us that the ground beneath our feet is alive constantly adjusting and constantly storing energy. In a country built on moving earth, preparedness is not paranoia—it is progress. The tremors may fade, but the lesson endures: the next cluster may strike anywhere, even beneath the capital. It is not a matter of if, but when.
