Explanation of deeper quakes

 The Deep quakes and plate tectonics

The plate tectonics fails to explain the deep quakes at 600 to 700 kms below Earthcrust.This is because the plate thickness are up to 100 kms .How come a rupture or relative motion at this much depth.
The answer given by plate tectonics is like this...
At subduction zone the plate  going below another plate, reaches the depth of 700 kms and then due to heat ,it dismantle from subducting plate,giving a jerk and hence a quake.
Now the question is...
1) The temp at 700 km depth is about 1000 degrees Celsius
2) The Earth crust melt at temp from 600 to 900 degree Celsius 1300 Celsius max.
Now the question is whether the defending plate can bear the temp of 1000 degrees ,without melting or atleast becoming fluid?
How come a fluid plate material can produce a jerk on mother plate,which is already melted or about to melt?
The explanation given is just an eyewash.
Now my explanation is...
There is water (in whichever form ,sponge or otherwise),below Earthcrust at a depth of 700 kms.The beauty of recent reserch says ,the water quantity is three times that of waters in all oceans.
Now when tidal pull exceed the limit ,on given date ,it breaks the surrounding mentle (material) and a deep quake occurs.
So ,tidal pull on water below 700 kms is the main reason of deep quakes.