A simple question to plate tectonics

 I am some time unable to solve some simple high school question ,when I try to learn plate tectonics ,specifically Earthquake occurance due to built up stress on plate boundaries

  Time and again ,we are told that the plates are moving and they built up stress at the plate boundaries. When these built up stresses are released suddenly it induces quakes. Also once the built-up stress is released, it takes years to built up again.
Now take up following quakes at Kermadec Island
1) 4th March 2021...17.41 UTC...7.4 magnitude...at 29.6 S and 177.8 W

2)4th March 2021....19.28 UTC..8.1 magnitude....at 29.7 S ,177.27 W

And today's quake at Kermadec
3) 16th March 2023 ...06.26 UTC, ..7.0 magnitude at 30.11 S ,176.11 W
There could be several more at Kermadec
Now look at  locations of quake in  year 2021 and today's quake, just two years later.
There is hardly any difference in epicenter
0.31 degrees in lattitudes and 1.16 degrees in longitudes
Now maximum distance at equator between two consecutive longitudes is 111 kms.Where as at 29 S it coukd be hardly 80 kms.
How come in two years such  great stresses are built up ?
  No seismologiat is ready to answer such questions, knowing well the answers.
  You can say it is residual stress ,because Kermadec have 7+ quakes very frequently
Any answer?