KORONADAL CITY, South Cotabato–Three strong undersea tremors struck several parts of southern Philippines on Thursday but there were no reported damage and no tsunami alert issued either, the United States Geological Survey (USGS) said.
The latest, a 4.5 earthquake, with a depth of about 620.9 km, occurred around 7:30 p.m. and was traced 110 km south west of Cotabato City.
Barely three hours before that, a 5.1 magnitude earthquake with a depth of 623.1 km and with epicenter of 110 km southwest off Cotabato jolted the cities of Pagadian, Zamboanga and in Manila, the USGS reported.
At around 3:30 p.m., a 6.4 magnitude tremor traced about 150 km south of Pagadian City with a depth 618.8 km jolted several parts of Mindanao.
There was no tsunami alert issued by the Pacific Tsunami Warning Center based in Hawaii.
Philippine Institute of Volcanology and Seismology director Renato Solidum said the three quakes were almost not felt by residents because they were too deep to cause any damages.
He said Thursday’s tremors were also part of aftershocks of July 24 strong quakes within Moro gulf off Mindanao Island.
“It’s only aftershocks and it will not trigger tsunamis,” he said.
On Saturday, three major earthquakes occurred in the south with more than 200 aftershocks but there were no reported damages.
The Philippines sits on the Pacific “Ring of Fire” where continental plates collide causing frequent seismic and volcanic activity.