Phivolcs warns of unstable ground in 38% of General Santos barangays

Another significant aftershock struck the region on Wednesday, adding to the ongoing seismic activity following the devastating June 9 magnitude 7.8 earthquake in Mindanao. According to the Philippine Institute of Seismology and Volcanology (Phivolcs), a magnitude 4.6 aftershock jolted Sarangani at precisely 4:03 p.m., with its epicenter located 50 kilometers southwest of Balut Island. This tremor, originating from tectonic forces, occurred at a depth of 25 kilometers beneath the Earth's surface. While the quake did not result in any reported damage, it served as yet another reminder of the lingering effects of the larger earthquake that had already shaken the region just over a week prior.

The initial mainshock on June 9, measuring 7.8 on the Richter scale, triggered a series of aftershocks that continued to affect communities across Mindanao. Among the most notable recent quakes was a magnitude 5.5 tremor that hit Glan, Sarangani, further illustrating the persistent seismic unrest in the area. These subsequent shocks, although less intense than the primary event, underscored the complex geological dynamics at play and raised concerns about the long-term stability of the region.

Phivolcs issued warnings regarding the potential for liquefaction, a phenomenon where saturated soil loses strength and cohesion during earthquakes, leading to ground instability. This risk was particularly pronounced in General Santos City, where at least 38% of the city’s barangays were identified as high-risk zones. Scientists noted that liquefaction could lead to serious consequences such as ground cracking, subsidence, and even the collapse of structures. The agency emphasized the importance of adhering to seismic design standards and conducting thorough assessments of building foundations in these vulnerable areas.

The aftermath of the June 9 earthquake saw extensive damage throughout Mindanao, with over 60 fatalities and hundreds of injuries reported. Infrastructure was severely impacted, with thousands of homes either destroyed or damaged. The situation in General Santos City was particularly dire, with more than 500 individuals injured and nearly 3,004 residences lost. The economic and social repercussions of the disaster were profound, affecting the lives of over 180,519 residents.

Phivolcs' experts, including Kathleen Papiona, highlighted that the earthquake originated from the offshore Cotabato Trench, indicating that the seismic activity was not linked to any active on-land faults. This clarification helped alleviate fears among local populations who might have worried about potential fault movements closer to their homes. However, the agency also warned that the region remained susceptible to liquefaction, emphasizing the need for continued vigilance and adherence to safety protocols.

As the days passed since the mainshock, the frequency of aftershocks began to decrease, though they continued to pose a threat to the region's stability. With over 5,000 aftershocks recorded, including more than 1,300 plotted on seismic maps and 76 felt by residents, the scientific community remained vigilant in monitoring the situation. The ongoing seismic activity serves as a stark reminder of the challenges faced by communities in seismically active regions and the importance of preparedness and resilience in the face of natural disasters.