The Earthquake epicenter is located next to the Japanese islands, as it is seen and labeled on the picture.
The tectonic plate that is to the right and below the epicenter is the Pacific Plate- this is easy to see on the picture.
The plate to the left is a little more confusing, but if you look closely, it is the Okhotsk plate- you know this because there are no boundaries between the name of the plate and the epicenter.
