DAVAO CITY --- Residents of some barangays in Davao City felt a strong tremor after a loud sound beneath bt the Philippines Institute of Volcanology and Seismology said it was a magnitude 3.5 of tectonic origin. The Phivolcs added that intensity 3 was felt in Davao City. The tremors were also felt in Mati City, Davao Orientaland Digoc Citt in Davao del Sur.