MANILA, April 22 (Xinhua) -- A 5.7-magnitude earthquake of struck northern Zambales province in the Philippine main Luzon island on Monday afternoon, the Philippine Institute of Volcanology and Seismology (Phivolcs) said.
The institute said the quake, which struck at 5:11 p.m. local time, hit at a depth of 21 km, about 2 km northeast of Castillejos town in Zambales province.
The quake, which was measured by the U.S. Geological Survey at 6.3 magnitude, was strongly felt in the Philippine capital of Manila.
No casualties and damages have been reported so far.
The Phivolcs said the tremor was tectonic in origin and aftershocks are expected.
The geographic and geologic settings of the country make it prone to earthquakes.