The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported that the movement of the Cotabato Trench, which triggered the Magnitude 7.8 offshore Sarangani Earthquake on June 8, caused parts of the coastlines in Sarangani and Davao Occidental to be pushed upward.

“This resulted in almost a 2-meter exposure of the seabed that was previously submerged underwater,” PHIVOLCS said on Monday morning.

The agency added that due to the uplift movement of the trench, the land along the shoreline expanded by up to 200 meters in some areas, and the level reached by seawater has changed.

“Such a landform formed after a strong earthquake does not indicate that a tsunami is coming,” PHIVOLCS pointed out. 

The institute found that a shore in Barangay Balangonan in Jose Abad Santos, Davao Occidental experienced a ~2.5 coastal uplift, causing a difference of >200m location of pre and post-earthquake high tide.  

“The event exposed a >50m wide reef of raised corals that were once completely submerged”, PHIVOLCS added. 

Following the June 8 earthquake, the agency also reported formerly submerged corals exposed on a co-seismically raised modern reef along the coasts of Barangay Pangyan in Glan, Sarangani.

PHIVOLCS, however, recently refuted misinformation claiming that the Magnitude 7.8 earthquake was caused by volcanoes beneath Sarangani Bay. 

The agency clarified that the earthquake is tectonic in origin, resulting from the movement of the Cotabato Trench, with no volcanoes located under the Sarangani Bay.