When an earthquake strikes, moments can spell the difference between life and death. That's why earthquake-prone locations like Mexico and Japan install earthquake early warning (EEW) systems. Performance and expense remain barriers to fuller implementation, but United States Geological Survey (USGS) researchers conclude EEW may be accomplished more efficiently - crowdsourced from your smart phone.
Less than a decade after its invention, the smartphone is now everywhere - six billion will be in use by 2019. Contrast this ubiquity with the relative scarcity of EEW systems, and it's easy to understand why scientists began to wonder what so many portable sensors could do for EEW efforts.
After measuring crustal deformations for the last two decades, "we thought that wouldn't it be cool if we could use a large number of less precise measurements (from smartphone GPS, for instance) to derive the same answer but for much less cost," says project leader Benjamin A. Brooks, an earthquake scientist with the USGS.
To answer this question, his team tested smartphones to determine their ability to detect tremors. By measuring the displacement recorded on a shaken phone and then comparing with a scientific EEW device, his team saw that smartphones can spot earthquakes of magnitude 7 and higher.
The next step was to test the smartphone's ability to provide crowdsourced advance earthquake feedback. Researchers tested smartphones against a simulated magnitude 7 earthquake along the Californian Hayward fault, and then against data from the 2011 magnitude 9.0 Tohoku-Oki earthquake in Japan.
In the Hayward experiment, smartphones were able to provide warning within five seconds, and able to pinpoint the epicenter to within 3.1 miles (5km). In the Tohoku-Oki offshore rupture simulation, the warning took 77 seconds, yet was fast enough to have permitted notice minutes before the tsunami made landfall and the most damaging waves reached Tokyo.
The researchers concluded smartphone EEW performance is extremely good relative to the specific hardware or software in the device. "We're surprised at the power of large numbers of observations, and we were surprised at how well you can do with smartphone GPS, " Brooks says.
Read the full study here.
Check out this week's feature to see how supercomputers give us a better look inside the earth.