In an zone between two plates, off the coast, where no one would immediately be affected, a 6.0 quake vibrated the earth monitoring equipment.

I include a map of the location.

Here is a list of the Quakes that struck on the 20th of April alone:

5.3 - 05:23:12 RYUKYU ISLANDS, JAPAN
5.3 - 03:28:55 RYUKYU ISLANDS, JAPAN
5.1 - 03:00:58 RYUKYU ISLANDS, JAPAN
5.1 - 02:48:05 PHILIPPINES
5.9 - 02:23:34 RYUKYU ISLANDS, JAPAN
6.1 - 01:45:57 RYUKYU ISLANDS, JAPAN
5.3 - 00:39:20 SOLOMON ISLANDS
5.6 - 00:31:01 RYUKYU ISLANDS, JAPAN
6.0 - 00:26:41 RYUKYU ISLANDS, JAPAN