The reason I think "hypothesis" vs. Theory matters is "intelligent design". They say evolution is just a theory and so creation science has to be taught. I just had to make sure I did not vote for a woman running for local school board here who wanted creationism (by name of intelligent design) to be taught.

OK, EQF, plates don't work like you suggest. It is not how earthquakes work. The plates are always moving smoothly at a distance from the fault. For example, GPS is used in the interior of plates to give the plate motions, and they do not stop and start. For the San Andreas fault proper, the lower ductile crust is always moving along. It is the upper crust that locks and flexes. So, geodetic (these days, mostly GPS) data will not show most of the block motion if they are spaced at 1 km across the fault, but they will show almost all of the motion if they are spaced at, say, 50 km away from the fault, on each side. During a quake with 5 m of slip at the fault, the GPS stations close to the fault will see almost all of this, and the ones spaced 100 m from the fault will see very little.

Same with Japan: part of the east coast of Japan was flexed by locking of the upper part of subduction zone (lower part more or less continuosuly moved). So, opposite where there was 20 m of slip on the locked fault, the coast moved up to 3 m. But, the west cloast of Japan moved very little, and the east coast of mainland Asia may have only move (I'm guessing) 1 cm.

OK, on the above I am qualified: this is structural geology and seismotectonics. I am sort of a structural geologist.

Here is where I need a little help: I think that a M9 like Japan may indeed have a very small affect on other boundaries around the same plate, in this case, the Pacific plate. But, I am not sure of this and would be interested in how much (1000ths of a bar? enough to advance a future quake by minutes or hours (say, from 100 years to 99 years 365.20 days?). Nearby parts of the same subduction zone likely have their future quakes advanced by a couple of years (from 100 years to 98 years, for example; these are the sorts of numbers I've heard for, say Landers quake affect on nearby faults.)

Arkansas is nowhere near a plate boundary. The interiors of plates can be under high stress because the rock is stronger. So, the stress is there, if you weaken the fault, you can get an earthquake. The most likely way to weaken the fault is fluids. Injections wells can certainly do that, but that does not mean that injection wells are causing the Arkansas swarms.

Chris