JAKARTA, Aug. 19 (Xinhua) -- A moderate quake measuring 5.6 magnitude on the Richter scale rocked Sumatra island of Indonesia earlier Wednesday, with no initial report of damage or casualty, Meteorology and Geophysics Agency said here.

    The quake struck at 00:58 a.m. Jakarta time (1758 GMT Tuesday) with epicenter at 87 km southwest Tanah Baya of North Sumatra province and at 32 km in depth, the agency said.

    The archipelago country with over 230 million population is laid on a vulnerable quake-hit zone so called the Pacific Ring of Fire, where two continental plates, stretching from Western hemisphere to Japan meet that cause frequent seismic and volcanic movements.