As a geophysics grad student, I have to point out that the North Korean test generated a minor seismic disturbance (around 4.2 or so). Given that naturally occurring 4.2+ earthquakes happen everyday, and much deeper underground than this nuke test, there is no reason to link the N. Korean test to earthquakes in Japan or Hawaii.
The US and USSR set off a lot of underground tests that were significantly larger than the N. Korean test, and there has never been a correlation found between those and increased seismic activity; even in the case of tests in Nevada triggering activity in California.
Besides, Japan is the most seismically active area in the world, and while it's true that 6+ earthquakes are not common in Hawaii, they are expected due to the volcanic activity and the major fault structures that develop along the flanks of the volcanoes.
You can look at earthquakes for the past week
here.
There are typically 300+ earthquakes per week just in CA-NV, when you count events down to the 1.0 magnitude range. You can also view world seismicity by following the link on the sidebar, which only displays events above 4.0. The North Korean nuke test was almost too small to even make it on the map.