As Elizabeth explains the Quake-Catcher network can provide denser observation of earthquakes, providing higher resolution imaging of earthquake ruptures. It can give detailed ground shaking across a region and could potentially also be used to rapid event detection after an earthquake starts giving valuable information to emergency responders.
The video below includes a visualisation of a quake in Christchurch, New Zealand. In the animation the colours indicate the strength of shaking in a given area, so the dark red shows strong shaking. You'll be able to see the wave propagating across the city and will notice that for some stations in Christchurch itself the shaking continues for a fairly long time. This is because the city is located on a very soft sedmentary basin which tends to resonate in these types of earthquakes.
Elizabeth will also be speaking at the ISGC2011 Distributed Desktop Grid and Volunteer Computing session this afternoon - do try to pop along!