QUITO, Dec. 23 (Xinhuanet)-- An earthquake measuring 6.1 on the Richter scale rocked the center of Ecuador and shook buildings in Quito, Ecuador's capital city in the north of the country, Ecuador's Geophysical Institute said on Friday.

The earthquake occurred at 16:47 local time (21:47 GMT). The epicenter was close to Puyo, capital of Pastaza province, 161 km southeast of Quito.

Only people at the top of tall buildings felt the quake, which caused scant damage.

The institute said that a collision between the Nazca ocean plate with the Ecuadorian continental plate caused the quake, forcing a noisy phenomenon called subduction.