More than 10 motorists became trapped overnight on a stretch of road after the shaking brought rocks, mud and boulders cascading down onto the roadway.
Taiwan's Central Weather Bureau said the quake struck at 2:10 p.m. local time about 140 miles east-southeast of Hua-lien at a depth of about 10 miles.
No tsunami was generated by the seismic event, which occurred near Japan's Sakishima Islands to the east of Taiwan.
No injuries were reported from what was Taiwan’s most powerful quake since the island was hit by a 6.9 temblor on Dec. 19, 2009.
In 1999, about 2,400 people died when a 7.3 magnitude temblor struck central Taiwan.