October 1, 2013
Last Tuesday, a 7.7-magnitude earthquake hit Pakistan, causing widespread destruction, the creation of a new island off the country’s coastline and at least 515 deaths.
Of course, there’s nothing we can do to prevent such disasters—earthquakes result from the shifting and collision of enormous, continent-scale tectonic plates over which we have no control. If we know a massive quake is about to strike, though, there may be measures we can take to better protect ourselves.
But how could we possibly know when a quake is about to hit? Seismologists are extremely good at characterizing the overall hazards that those living in fault zones face, but they’re far away from being able (and may never have the ability) to predict exactly when an earthquake will strike.
Undeterred, several different teams of scientists are hatching plans for a new kind of solution. And the key to their success may may be the smartphone in your pocket.
Their idea takes advantage of the fact that most new smartphones include a tiny chip called an accelerometer. These chips measure the movement of the phone in three directions (up-down, left-right, and backward-forward) to customize your experience as you use the phone—for example, rotating the display if you turn the device.
As it happens, seismometers (the large, expensive instruments used by geologists to detect and measure earthquakes) do essentially the same thing, albeit with much more accuracy. Still, the tiny accelerometers we already carry around with us all the time could allow scientists to gather much more real-time data than is currently available—there are countless times more smartphones than seismometers, they’re much cheaper and they’re already deployed in a wide range of locations—if they can actually measure earthquake movement with sufficient precision.
Recently, Antonino D’Alessandro and Giuseppe D’Anna, a pair of seismologists at Italy’s Istituto Nazionale di Geofisica e Vulcanologia, set out to resolve this question. To assess the accelerometers—specifically, the LIS331DLH MEMS accelerometer used in iPhones—the duo placed five iPhones on a vibrating table in a variety of positions (flat, angled on top of a wedge-shaped piece, and vertical) and compared the data they recorded with a professional-quality earthquake sensor for reference.
Their results, published Sunday in the Bulletin of the Seismological Society of America, showed that the iPhone accelerometers performed even better than they expected. “When we compared the signals, we pleasantly surprised by the result—the recordings were virtually identical,” D’Alessandro says. “An accelerometer that costs a few dollars was able to record acceleration with high fidelity, very similar to a professional accelerometer that costs a few thousand.”
There are some limitations: the iPhone accelerometers aren’t as sensitive to weak vibrations, so during the tests, they were only able to record movements that correspond to earthquakes that would register as magnitude 5 or higher. But ”these limits will be overcome in the near future,” says D’Alessandro. “Because these chips are widely used in laptops, games controllers and mobile phones, research into improving them is going on around the world.”
The next step would be developing software to allow normal users to harness these accelerometers’ capabilities, turning their smartphones into mobile earthquake sensing systems. Last December, Berkeley researchers announced plans to develop an app that would allow users to donate their accelerometer data to earthquake research. Stanford’s Quake-Catcher Network and Caltech’s Community Seismic Network—both of which use small purpose-built seismometers that are distributed to volunteers and plugged into their computers—could serve as a model for this sort of network.
Once in place, the network would be able to gather a huge amount of data from thousands of geographically-dispersed users, allowing researchers to see how quakes move with finer resolution. If enough phones are on this network, emergency workers may be able to quickly gauge where they could most efficiently devote their time after a quake hits.
But how do you go from documenting earthquakes to warning people about when dangerous shaking will occur? As The Atlantic points out, the key is that earthquakes are actually comprised of two types of waves that ripple through the earth: P-waves, which arrive first and are difficult for humans to sense, and S-waves, which typically come a few seconds later and cause the majority of the physical damage.
If we had software installed on our phones that automatically detected strong P-waves and sounded an alarm, we might have a few scant seconds to take cover before the S-waves hit (officials recommend dropping to the ground, huddling under a stable table or desk and getting away from windows and doors). It’s not much, but in some cases, a just a few crucial seconds of warning could make all the difference.
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