Twitter
The USGC, which has been tapping into tweets since 2009, relies on Twitter data as a secondary source to pick up information about earthquakesReuters

The US Geological Survey (USGS) can detect an earthquake in a matter of seconds using Twitter while its conventional sensors take much longer. The agency's Tweet Emergency Dispatch programme, which automatically sorts tweets about earthquakes to detect seismic activities across the world, sounded an alert on the 2014 quake in California in a mere 29 seconds.

"It's not a revolutionary change in what we do, but it just gives us that extra minute to start on our response," Paul Earle, a seismologist at the federal agency, was quoted as saying by CNN.

The USGC, which has been tapping into tweets since 2009, relies on Twitter data as a secondary source to pick up information about earthquakes. "The data stream from Twitter is totally independent. It's a secondary check," Earle said.

According to Twitter's blog post, the programme filters out tweets with more than seven words and tweets containing links. The reason for this, it said, was that people experiencing tremors won't post long tweets and links. The USGS also said the programme can find out whether an earthquake detected by its sensors is accurate or false.

Twitter employee Elaine Ellis said: "Using Twitter data, their (USGC) system was able to pick up on an aftershock in Chile within one minute and 20 seconds – and it only took 14 Tweets from the filtered stream to trigger an email alert."

In a day, around 70 possible earthquakes are processed by USGC but only "a small handful of these might be felt". The USGS has 2,000 seismic sensors which are mostly based in the US.