The seconds between the warning of an impending earthquake and the moment the quake hits can be the difference between life or death. In that time, automatic brakes can halt trains; people can duck for cover or rush for safety. But current warning systems aren’t always where they are needed, and scientists don’t fully understand what determines the size and location of earthquakes. Nearly 10,000 people were killed in earthquakes in 2015, the majority from the devastating Nepal quake. The federal government estimates that earthquakes cause $5.3 billion in damage per year to buildings in the U.S.
Ground-based sensors help warn of quakes, but they have their limits. Now, a group of researchers at Columbia University are taking measurement somewhere new: underwater. They’re designing a system that could lead to faster warnings for people living near areas affected by underwater earthquakes and tsunamis. If they succeed, they could help reduce the damage caused by these natural disasters and save many lives.
I recently visited a laboratory at Columbia’s Lamont-Doherty Earth Observatory, in Rockland County, New York, where a technician was testing pieces of the boxy, three-foot-long underwater seismometers under a microscope. The lab’s floor-to-ceiling shelves were stacked with bright yellow and orange parts that will have to endure crushing pressures on the ocean floor at depths of thousands of feet for years at a time.
The networks of land-based earthquake monitors around the world warn of quakes by watching for changes in pressure and seismic signals. Underwater sensors could more accurately locate underwater earthquakes than ground-based networks, says Spahr Webb, the Lamont-Doherty researcher leading the project, because “the system is designed to be deployed over the top of a large earthquake and faithfully record the size and location of both the earthquake and the tsunami. … By installing pressure and seismic sensors offshore you get a much more accurate determination of location and depth of a nearby earthquake.”
Webb pointed out the crab-like shape of a thick steel shell that is designed to prevent the seismometers from being pried from the sea floor by fishing trawl nets. “Keeping these things where they belong is the key,” he told me.
When they are launched about a year from now, 10 to 15 seismometers will be carefully lowered by a crane from a ship to the seabed. Similar to the land-based monitors, they will contain sensitive pressure sensors and accelerometers to measure and separate out seismic and oceanic signals. These sensors will monitor subduction zones, the areas where one plate of the earth’s crust slides under another. An earthquake produces a tsunami at a subduction zone when an underwater plate snaps back like a giant spring after it is forced out of position by the collision of an adjacent plate.
According to Webb, the land-based seismometers monitoring the regions that produce the largest tsunamis are sometimes more than 100 miles away, which hinders speed and accuracy. “A big motivation for the offshore observations is the size of the tsunami from any given earthquake has a large uncertainty based on land observations alone,” says Webb. In Japan, after the devastating 2011 earthquake, an expensive cable with numerous sensors was installed offshore to speed up warnings and boost accuracy. Now the Columbia seabed-based seismometers will obtain data in regions of the globe with similar tsunami hazards as Japan to augment land-based early warning systems.
The project is not alone. Columbia’s seismometer system is just one of a wide array of new earthquake-monitoring technologies that are being developed. “There are many exciting techniques coming online,” says Elizabeth Cochran, a geophysicist with the U.S. Geological Survey.
While the ocean depths offer opportunities to monitor quakes close to their source, for instance, watching from space could provide a wider view. Scientists at University College London have proposed launching several small satellites to look for signs of earthquakes using electromagnetic and infrared sensors. So far, experiments have proven that the concept works, but a problem has kept the project from getting off the ground: Electromagnetic and infrared signals are emitted by all sorts of things, natural as well as man-made.
Dhiren Kataria, one of the leaders of the proposed project, which has been dubbed TwinSat, hopes that using a large enough number of satellites should allow researchers to separate out the seismic from the non-seismic events. Multiple satellites would also provide extensive global coverage, because each would orbit the earth every 90 minutes, he adds.
The TwinSat team has previously failed to get funding from the U.K. Space Agency, but it plans to resubmit its proposal in the next few months. If approved, the team could launch its satellites within three years, Kataria claims. To keep costs low, the satellites are designed to be small and use some off-the-shelf commercial components.
Another approach researchers are using is turning cell phones into science instruments. The app MyShake constantly runs a phone’s motion sensors to analyze how it’s shaking around. If the movement fits the vibrational profile of an earthquake, the app relays this information along with the phone’s GPS coordinates to the app’s creators, the seismological laboratory at the University of California, Berkeley, for analysis.
While the app’s not intended to replace traditional seismic sensor networks like those run by the U.S. Geological Survey, says Richard Allen, the seismological laboratory’s director, it could provide faster and more accurate warnings through vast amounts of crowd-sourced data. More than 250,000 people have downloaded the app since it debuted a year ago.
Quicker warnings like these can be used improve safety by being incorporated right into existing infrastructure. San Francisco’s Bay Area Rapid Transit has integrated Allen’s earthquake warnings into its system so that trains automatically slow when they receive a signal that an earthquake will hit. The system relies on the fact that the electronic signals from monitoring stations travel faster than seismic waves, giving the brakes time to act. “I can push out the warning before many people can feel the tremors,” Allen says.
Even better than faster earthquake warnings would be a way to predict quakes. Researchers at Los Alamos National Laboratory are using artificial intelligence to simulate earthquakes so that they can forecast when they will occur. But Cochran of the USGS doubts it will ever be possible to reliably predict quakes. “Earthquakes are very complex,” she says. “It’s hard to predict such chaotic systems.”
