They ARE two different quakes - one in Japan area, another in New Zealand/Kermadec Island area. I think what is getting confused is that there are several listings for the Kermadec Island one - making it look like there were several quakes instead of one. And most don't know offhand where Izu islands are so thought it was part of the ones listed for Kermadec islands area.
It DOES get annoying when there are different reports from different sensors -for the same quake- and people start freaking out "oh there were 3 mag 6 quakes!".
But the ones you are referring to are in two different geographic areas.