Four years ago today, 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.
Both earthquakes were generated by the same fault, the Masbate segment of the notorious Philippine Fault that has generated several deadly earthquakes in the recent past. Since the start of instrumentally recorded earthquakes in the 1970s, the most powerful of these Philippine Fault earthquakes has been the magnitude 7.8 Northern Luzon earthquake of July 16, 1990. Generated by the Digdig segment of the Philippine Fault traversing the provinces of Nueva Ecija and Aurora in Northern Luzon, this tremor was more than forty times more powerful than the 2020 Masbate earthquake, wreaking havoc in much of Luzon, killing more than 2,000 individuals and destroying infrastructure worth several billion dollars.
The occurrence of the two successive Masbate earthquakes within a short period of time (17 years) along the same fault segment is an extremely rare phenomenon, almost defying the current understanding of earthquake dynamics. When a fault ruptures, the earthquake that it generates is a manifestation of the energy released along such fault. This fault is not expected to move again soon, until such time that enough stress has reaccumulated on it which can take hundreds or even thousands of years, not 17 years.
If you can’t beat them, study them!
At the recognition ceremonies of the graduating batch of the College of Science of the University of the Philippines in Diliman, held on July 27, 2024, two students of the UP National Institute of Geological Sciences were recognized for their works towards a better understanding of earthquake processes in general, and the behavior of the Masbate segment of the Philippine Fault in particular.
Abigail Manahan, who graduated Magna Cum Laude, was bestowed the Leticia Ramos Shahani Award for best undergraduate thesis in Geology for her work entitled: “Geomorphology and Deformation of the Masbate Segment of the Philippine Fault: Insights from Ground Rupture and Riedel Shearing in Barangay Matugnao, Palanas, Masbate.” Deo Carlo Llamas, for his part, was nominated for Most Outstanding MS Graduate with a master’s thesis entitled: “Surface Rupture and Fault Characteristics Associated with the 2020 Magnitude 6.6 Masbate Earthquake.”
Both Abigail and Deo have demonstrated that disastrous natural processes such as earthquakes can be turned into research aimed at understanding such phenomena themselves. Using as center-piece in their studies a three-legged coconut tree split twice by the Masbate earthquakes of 2003 and 2020, both Abigail and Deo are contributing in the advancement of knowledge in earthquake prediction, the ultimate goal of most, if not all earthquake scientists around the world. It is just unfortunate that while no one wishes for earthquakes to happen, without them it would be impossible to understand these phenomena, and would continue to threaten an unprepared society with their attendant hazards. – Rappler.com
Mario A. Aurelio, PhD is a professor at the National Institute of Geological Sciences – University of the Philippines, and head of the Structural Geology and Tectonics Laboratory of UP NIGS. He mentors students interested in the study of earthquakes.