A research group says its analysis indicates tsunami waves reached Yonaguni Island in Japan's Okinawa Prefecture about 15 minutes after a powerful earthquake occurred near Taiwan on April 3.

The team includes Professor Imamura Fumihiko of Tohoku University's International Research Institute of Disaster Science.

The group used the quake's source fault data from the US Geological Survey to run a simulation on how the tsunami spread.

The researchers say the results show that tsunami waves were generated immediately after the quake and reached Yonaguni Island in 15 minutes.

They also estimate the tsunami reached Ishigaki Island in about 30 minutes, Miyako Island in 40 minutes and the city of Naha in an hour.

Japan's Meteorological Agency issued a tsunami warning for Okinawa Prefecture following the quake, projecting waves of up to 3 meters.

But the maximum height of observed tsunami was 30 centimeters.

The group suggests that the quake happened across both land and sea, and this limited seismic energy in the sea that causes tsunami. The team says that appears to explain why the tsunami was relatively small despite the quake's magnitude of 7.7.

Imamura said the simulation results show that the tsunami reached Okinawa Prefecture very quickly.

He added there are many tourists on the beaches of Okinawa and it is necessary to examine the responses taken this time, including how they were guided to evacuate.