There are two aspects to your question. The first one is the intensity of that fracturing event--how destructive it can be and how big it can be.
As Dr. Boerner was saying, the industry is putting seismographs in adjacent wells to record the earth movement at the time of fracturing. They are recording those values and expressing them in terms of the Richter scale, as for any other type of earthquake.
You may not know that on the Richter scale there are negative values; at the time they defined the Richter scale, the smallest earthquake they could register was given a zero value, but with more modern instruments we can go into negative values for smaller earthquakes. The intensities of those fracturing events are between -2 and -3 on the Richter scale, so these are very small seismic events that are recorded.
With reference to the permeability or the preservation of the water or the gas in the rock, in most of the shale gas rocks in Canada the gas was generated hundreds of millions of years ago, and it's still trapped in those rocks. That means that the geological system was fairly impermeable.
We have some other examples in Quebec, for example. There is an old gas field that has been exploited near Quebec City. It's called the Saint-Flavien gas field. That gas was generated by the Utica shale and has been trapped in that conventional reservoir, overlaid by the Utica and the Lorraine shale. The gas has been there for 450 million years. Those geological systems are very impermeable systems.