Why doesn the gate room shake anymore when the Stargate is activated?
Probably for the same reason the SG-1 team doesn’t arrive with ice crystals on their faces anymore (as they did in the pilot episode, “Children of the Gods”). Or, maybe General Hammond ordered them to install shock absorbers. It is stated in a conversation between Jackson and Hammond in the first season episode “Solitudes” that the frequency dampeners had been installed in the base. The second Stargate on Earth was located by the seismic tremors that it caused.