some questions to plate tectonics

There are several major quakes from 27th February 2010 to 28th February. There are questions for plate tectonics here
1) Why there are major quakes on some particular date?
2) How these quakes,on different plates can be explained ,if they occur on the same date?
3) How the stresses on different plates are released on a single day?
yes,quakes do occur on plate boundaries and that ,there are plates and they are moving. But the fact is
1) Plate boundaries are weaker sections and hence they break earlier due to tidal force.
2) Plates are due to quake and quakes are not due to plates

How the first break in plate occurred?Due to heat currents of molten magma?
The earth crust would not have solidified at he place where splitting heat currents were already present.