JAKARTA, Indonesia (October 8, 2012)--A strong undersea earthquake hit parts of eastern Indonesia Monday, but there were no immediate reports of damage or casualties.

The U.S. Geological Survey said the 6.3-magnitude quake struck at a depth of 21 miles about 86 miles southeast of Ambon, the provincial capital of Maluku.

Indonesia is prone to seismic upheaval because of its location on the Pacific "Ring of Fire," an arc of volcanoes and fault lines encircling the Pacific Basin.