As a colorful globe spins on a 30-inch monitor, Jesse Lawrence clicks his computer mouse and a bright red dot appears in the Far East—marking an earthquake that happened during the week just past. Another click, and pink lines are visible in the Pacific Ocean, designating some of the Earth's plate boundaries, where most earthquakes occur. One more click, and Earth is shown in “night view,” with metropolitan areas defined by clusters of light, in stark contrast to the darkness of largely unpopulated countries.
“This is a great way to view the Earth to teach seismology,” the assistant professor of geophysics says. “Where populations and earthquakes overlap, you have the greatest seismic hazard.”
But as captivating as the interactive program is, Lawrence says the earthquake detection software he and Elizabeth Cochran, a seismologist at UC-Riverside, are developing is the genuinely cool stuff. Their Quake-Catcher Network will enlist volunteers whose laptops have sudden-motion sensors, or accelerometers, to detect earthquakes. Desktop computers also can be equipped with motion sensors that plug into a USB port via cable, at a cost of $30 to $100. Ultimately, the network of laptop and desktop users might be used to issue early warnings to the public.
Since 2005, many laptops, including Macs and ThinkPads, have been designed with accelerometers. “The idea is that when you knock a laptop off a coffee table or shelf, which will inevitably happen, [the motion sensor] will hold the head off the hard drive and lock it there—so that when the laptop hits the ground, the head won't hit the drive,” Lawrence says.
He and Cochran, who were postdocs together at Scripps Institute of Oceanography, hypothesized that earthquake detection could be done better and faster with lots of low-grade sensors than with fewer, more expensive research-grade sensors, which can cost $10,000 to $50,000. Lawrence wrote a base code, “sort of a clunky version” that worked “just fine,” and they did simple tests that included leaving a laptop running in a closet for three months. Result? “We were able to detect a 3.7.”
The next step was to ask if the seismic signals they could get from laptops could be networked together. But how many laptops would it take to detect earthquakes? The answer, Lawrence says, is “We don't know. It depends on the size of the earthquake you want to look at.” For example, there probably will never be enough laptop sensors in any given area to detect earthquakes of a 2.0 magnitude. “But if we had 1,000 sensors in the Bay Area or in Los Angeles, looking for a 3.0 would be possible,” Lawrence says.
“We have about 382 volunteers running the software on the Macintosh beta version,” Lawrence says. “And we have about 1,000 volunteers ready to sign up, using PCs, whenever we release the beta version for that.” People can join the network online (qcn.stanford.edu).
Lawrence says there currently aren't enough users for it to be “an active system” that is viewed in real time. But he and Cochran have submitted an article to Nature magazine that “proves that we can record earthquakes well with laptops, based on multiple sensors that recorded the same earthquake in Reno [Nev.].”
