Is it possible to prevent high magnitude earthquakes by induced earthquakes?
The idea of trying to limit energy released by earthquakes and the damage that may result via the use of controlled smaller blast induced quakes is an interesting idea.

One of the problems with this is that we don't know enough about the snags along faults that cause stresses to accumulate during the normal movements along a fault. We also don't know enough about fault surfaces (shapes, undulations and friction factors) of individual fault surfaces. The other thing we don't know is where the snags are located on fault surfaces: along and down the fault surface.

The strength of snags is one factor which determines how much energy accumulates and is eventually released suddenly when the snag fails.

The other factor is the type of movement at the fault zone. Do the fault surfaces slide past one another laterally, does one sub-duct beneath the other, or are they spreading apart.

With some faults, wedge failures may produce large blocks that act a snags. Other snags can be very hard, strong protrusions of rock firmly cemented in the fault surface. Corrugations can also act as snags.

Another possible mechanism by which quakes can happen, particularly in the subduction zone is that part of the fault surface that is riding over a subduction zone might hang with no support, due to undulations or point support. If the overhanging rock is not strong enough it can fail and drop. The impact of the dropping block then causes an earthquake.

The ways in which earthquakes occur are varied and sometimes complex.