Each year, there are 15,000 or more earthquakes shaking the ground around the world. Many of these are devastating quakes with magnitudes of more than 5.0, according the United States Geological Survey.
In the U.S., we take for granted that we'll be warned about these quakes almost immediately after their first detected. The USGS has about 2,000 earthquake sensors. Yet, around the world many quakes simply happen with virtually no alert system in place.
The consequences can be devastating. But the USGS has found a novel way to detect quakes where they don't have detectors, and warn people to seek safety. That tool is Twitter.
It turns out the social media site, with 320 million active users, is a good source for almost instantaneous alerts about quakes. (See photos next page.)
The USGS is using Twitter's application programming interface (API) to access its stream of global activity. It found that people who are feeling an earthquake, or just did, tend to write short tweets of seven or fewer words, like "earthquake?"
So, they filtered out Twitter tweets longer than seven words. Plus, the USGS discovered that people tweeting the magnitude of a quake tend to be people hearing about it on the news and, often, who live far from the quake. So, they filtered out tweets with numbers.
The result is fast alerts that can save lives. In fact, the USGS can now typically alert people in affected areas in about two minutes.