ZAMBOANGA
A magnitude-6 earthquake shook people from their sleep in the Philippines' capital Manila early Sunday, but there were no immediate reports of injuries or damage.
The Philippine Institute of Volcanology and Seismology reported that the tremor's epicenter was centered under the sea around 43 kilometers (26 miles) south of San Antonio in Zambales - northwest of Manila - at a depth of 85 kilometers.
It struck at around 3:32 a.m. (7:32 p.m. Saturday GMT).
Three more quakes followed over the next three hours - a magnitude 4.2 around 74 kilometers south of Jose Abad Santos in Davao Occidental in the country's Muslim south, an intensity 2.3, 20 kilometers west of San Antonio in Zambales, and a 2.5 about 36 kilometers south of Don Marcelino again in Davao Oriental.
Although no damage was reported, the institute said more aftershocks were expected.
The Philippines archipelago lies in the Pacific Ocean's “Ring of Fire,” where such tremors and volcanic activities are common.
A magnitude-7.7 quake killed nearly 2,000 people across the main northern Luzon island in 1990.
