IEEE Spectrum June, 2015 - 16

waves, along with GPS sensors to detect
permanent ground movement due to
the motion of the geological fault that
triggers the earthquake.
Battalgazi Yildirim, founder of Zizmos,
based in Palo Alto, Calif., thinks he can
get as good-or in some cases even
better-earthquake data from a network of cheap sensor packages. These
are made up of microelectromechanical
accelerometers attached to inexpensive,
off-the-shelf cellphone equipment that
manages data gathering and communication. "The sensor packages used by
the USGS cost about [US] $30,000 each,"
he says. "We're putting out sensors that
cost $100 each to build."
The network should have virtually
no installation or maintenance costs,
because Yildirim plans to rely on the
kindness of the crowd. Zizmos asks for

JUn 2015

nORTh aMERICan

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WarNiNg iN Need: Emergency rescue workers
carry a victim of the Dharahara Tower collapse
in Kathmandu, Nepal. Engineers are developing
more affordable earthquake warning systems.

GPS sensors in people's phones and navigation systems, he says. GPS-equipped
cellphones are ubiquitous in developing
countries, and such a crowdsourced system would offer early warning at practically no cost. "A country like Nepal, with
high earthquake hazards and minimal
resources, is where a crowd sourcing
approach would be most effective,"
Brooks says.
In research presented in the journal
Science Advances two weeks before the
Nepal quake hit, Brooks and his colleagues tested the ability of consumergrade GPS devices to detect earthquakes.
They subjected a Google Nexus smartphone and a commercial GPS module to displacements ranging from
10 centimeters to 2 meters. Both GPS
sensors picked up the smallest motion.
Next, the researchers performed
simulations using data from a hypothetical magnitude-7 earthquake in
northern California and from the real
2011 magnitude-9 earthquake that hit
Tohoku-oki, Japan. They simulated
volunteers to donate a tiny bit of interior smartphone responses based on census
wall space and a power outlet to host a data around the earthquake epicenters
sensor package, which is about the size and recorded a phone as triggered if it
and its four nearest neighbors measured
of a deck of cards.
With a $150,000 research grant from more than 5 cm of movement. If at least
the National Science Foundation, the 100 phones were triggered, the system
company was to launch a trial this May, declared an earthquake.
It took fewer than 5,000 smartphones
after this issue went to press, involving
268 sensors distributed in California. to detect the simulated California earthWhen a sensor detects a rumble, it will quake within 5 seconds, giving enough
send information about the time of the time to warn San Francisco and San Jose.
event and the magnitude of the shaking For the Japan quake, which had an offto a cloud-based server; algorithms will shore epicenter, detection occurred at
check reports from neighboring sensors just over 80 seconds, too slow for the
to determine whether the vibration was closest onshore towns but in enough
local-say, from a truck going by-or felt time to issue a warning to Tokyo.
"Sadly, on the Wednesday before the
elsewhere. If the latter, the system will
calculate a hypothetical epicenter for Nepal earthquake I had a discussion with
the earthquake, the original time of the a Nepalese colleague about proposing
event, and an estimated magnitude. For precisely such an approach," Brooks
earthquakes with magnitudes greater says. "There would be challenges in
terms of cellphone service in such a
than 4.0, it will issue an alert.
Benjamin Brooks, a geophysicist with mountainous region, but we think it
the USGS, has a different crowdsourcing would be doable there eventually."
approach in mind. Why not tap into the -pr achi patel & tek l a s. per ry

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Table of Contents for the Digital Edition of IEEE Spectrum June, 2015