Is it scientifically possible to force an earthquake?

Possible, yes. Practical, definitely not.

The only hope mankind of have to trigger an earth quake would be to trigger a very very large explosive at sufficient depth to cause the tension in the fault to release. Doing this would require us to know what the tension of the fault is so we can place a large enough device to overcome the resistive forces of the fault...which begs the question; If we find a way to measure the tension in the fault, then why not just evacuate when it gets within, say, 5% of critical, rather than try and trigger it to release, ourselves.

Yes! They use H.A.A.R.P. for this: 'High Frequency Active Auroral Research Program'. You can look at their: Ionospheric reflection, European Incoherent Scatter Scientific Association, HIPAS-High Power Auroral Stimulation, Poker Flat Research Range, Sura Ionospheric Heating Facility, SuperDARN, Weather Modification Operations and Research, Nikola Tesla.

I should think disturbing fault line to create an earthquake would be a bit of a doddle for H.A.A.R.P.

No not at this time with our present technology.. Many A bombs and H bombs have been detonated in the past and no earthquakes have happened. Still if detonated in the right place could be possible But i am only speculating.

At our current scientific state, its a question of how big the bombs have to be. In that case, it might cause more harm than just preparing for the quake and letting it happen...

No. Not possible at all. Period. Full Stop.