A small earthquake hits, sending curtains swaying and knickknacks rattling. After a few moments the shaking settles down, and for many people, their next move is to go online to the U.S. Geological Survey's Did You Feel It? website. There they can enter their address and the current time and answer questions about whether the shaking was enough to displace their furniture or wake them from sleep.
The USGS uses that information to put earthquake data on a real-time updated map. Users can check out the data set they've contributed to.
Did You Feel It? is the best-developed citizen-based earthquake science project today, writes Richard Allen, a seismologist at the University of California, Berkeley, in a commentary in the Jan. 20 issue of the journal Science. But it's not the only one. Portable sensors and people's online contributions help scientists gather earthquake information from all around the world.
Citizen science activities such as earthquake reporting are growing more popular as technology makes sophisticated instruments more available to the public. Citizen science earthquake projects promise to increase the number of seismic sensors on Earth at least tenfold, Allen writes.
The journal Science reports on several ways that everyday citizens voluntarily and involuntarily tell scientists about where earthquakes are happening around the world:
The European-Mediterranean Seismological Center examines its website traffic to discover when and where earthquakes happen. After an earthquake, many residents of Europe and the Middle East visit the center's site to learn about what they just felt, creating a surge in traffic that the site recognizes as coming from quake eyewitnesses. The site logs visitors' IP addresses to determine where they're located. These web-logged quakes are typically detected within 30 to 90 seconds of the earthquake's occurrence, according to the seismological center's website.
The U.S. Geological Survey monitors tweets that say earthquake. The tweets can tell the agency about broad earthquakes that many people feel. However, they don't give accurate location information. Survey scientists are studying whether they can extract accurate magnitude information from tweets.
The iShake Cal app, created by UC Berkeley's civil engineering department, records seismic waves from users' iPhones, then transmits that data to a central server.
People can request a USB sensor from Stanford University's Quake-Catcher Network that plugs into their laptops or desktop computers. The sensor sends seismic information to Stanford. If many devices in one area report movement, then researchers know that it's more likely to be an earthquake than an instance of someone jostling his laptop.
Of course, these detectors are much less sensitive than professional equipment, but they work for earthquakes of magnitude 5 and above, according to the new Science commentary.
Those interested in submitting more sensitive seismic information can request a detector to attach to their houses. The Quake-Catcher Network and the Community Seismic Network both offer building detectors, which work for earthquakes of magnitude 3 and above. The USGS offers sensors of even higher quality, through their NetQuakes project. All the projects let users peruse the data they and their neighbors create.