Earthquake ?

Many Sydney people are pondering the possibility of an earthquake - following the claim by academics that the quake that devastated Newcastle two decades ago was primarily caused by underground coal mining.
Sydney is removed from " the ring of fire " - seismic activity that runs through New Zealand, across the Pacific and continues through New Guinea and into Asia. We get the odd tremor every few years, but damage causing tremblors are virtually unknown.
It is a reasonable hypothesis. Long wall mining leaves vast caverns and it could well be that subsidence under Newcastle was the trigger for that quake.
What concerns some Sydney people is the plan by the New South Wales government to supplement the Sydney water supply by drawing from the aquifers in the southern highlands.These aquifers hold about three years supply of Sydney's needs - and will take between five and seven years to refill when depleted.
Thats a lot of water - and a lot of air space underground when the water is removed. Water can not be compressed, hence subsidence is impossible when that air space is filled with liquid but it's removal introduces a risk that has not so far been taken into account.
At this stage it is conjecture. There is no proof that tapping the acquifers will introduce risk, and yet there is also no rebuttal to the theory.
Sydney is desperate for water and those acquifers must be tempting to government planners - but if they go ahead with their plan to tap them - and somewhere down the track there is a devastating earthquake the blame will rightly reside on their shoulders.
Tapping acquifers is an unknown science. The government may be wise to avoid that risk - and go ahead with plans for a major desalination plant instead !