Buildings shook in Taipei early on Wednesday morning as two earthquakes in quick succession, the strongest with a magnitude of 6.6, struck southeastern Taiwan, but there were no immediate reports of damage.
The deepest had a depth of 30.6 km (19 miles) and the other one was 19.3 km deep. They could both be felt across Taiwan, with the epicenters in Hualien county - one just offshore - and close to the city of Taitung, the weather bureau said.
Hualien and Taitung are both mountainous, relatively sparsely populated areas.
Taiwan lies near the junction of two tectonic plates and is prone to earthquakes.
More than 100 people were killed in a quake in southern Taiwan in 2016, while a 7.3 magnitude quake killed more than 2,000 people in 1999.