Twitter asks did the earth move?

Twitter is being used by the US Geological Survey (USGS) to get instant public reaction to earthquakes.

This report from the BBC says that

The agency is trawling the messages to find out what people felt during a tremor - whether there was a lot of shaking in their area or not.
There are big spikes in Twitter traffic immediately following a quake and the USGS believes emergency responders might find the information useful.
It could help them assess very quickly the severity of a particular event.

However,

the survey stressed that the social networking tool would only ever supplement the existing scientific reporting systems which determine shake effects.