MANILA, Oct. 29 (Xinhua) -- The Philippine Institute of Volcanology and Seismology (Phivolcs) has upgraded the magnitude of the earthquake which struck Cotabato province in southern Philippines on Tuesday from 6.4 to 6.6.
The institute said in an updated report the inland tremor, which struck at 9:04 a.m., hit at a depth of 7 kilometers, about 25 kilometers southeast of Tulunan town.
The earthquake, which was tectonic in origin, can cause damage and that aftershocks are expected, the institute said.
The earthquake was also felt in strongly in Kaidapawan City, Sarangani province, Davao City, Koronadal City, Cagayan de Oro City, General Santos City, Zamboanga City, and Bukidnon province.
Local officials in the affected provinces said the strong earthquake sent panicking people out of their houses and buildings.
The officials said that tremor cut the power supply in many of the affected provinces, knocked down electric posts and shattered glasses in some of the establishments. Patients of a local hospital were evacuated out of the building, they added.
Cotabato and its neighboring provinces on Mindanao island are still recovering from the October 16 magnitude 6.3 earthquake that rattled the region, in which at least six people were killed and 167 injured.
The Philippines has frequent seismic activity due to its location along the Pacific "Ring of Fire", registering quakes everyday, though most are not felt.
Phivolcs records an average of 20 earthquakes a day and 100 to 150 earthquakes are felt per year.