ByRobin George Andrews
Published September 21, 2023
• 8 min read
The holy grail of seismology—the ability to predict the exact location, magnitude, date, and time of the next damaging earthquake—may one day be found hidden in symphonies of seismic waves. But for now, anyone claiming to possess that preternatural ability is either deluded or a charlatan. Apps and software that can let you know than an earthquake is imminently about to hit, however, are real—and may one day save your life.
Quakes happen quickly—but seismic waves “travel more slowly than signals on our cellphones,” says Judith Hubbard, an earthquake scientist at Cornell University. That means that if you are standing far away enough from the start of that evolving rupture, a warning system that relies on a quick-thinking autonomous network of quake-detecting instruments could send you a message to seek cover before the most violent shaking arrives.
You will only have moments to react. “In the vast majority of cases, it’s likely going to be seconds” before the earthquake arrives, says Robert de Groot, the ShakeAlert National Coordinator for Communication, Education, and Outreach at the U.S. Geological Survey. But seconds are better than no warning whatsoever.
Not all earthquake early warning system are the same. The effectiveness of these apps and systems depends on many factors, from the technology they rely on to the country you are in.
Here’s everything you need to know about these systems: how they work, why they may shield you from harm—and why they won’t be enough to prevent a tragedy by themselves.
An algorithmic ear to the ground
The ShakeAlert Earthquake Early Warning System, managed by the U.S. Geological Survey (USGS), operates in California, Oregon, and Washington—three states under the constant threat of a major and potentially devastating temblor. “We’re now fully operational in three states, supporting about 55 million people,” says de Groot.
The ShakeAlert system relies on a dense ground-based array of seismometers along the West Coast. Data on any ground shaking is recorded by this network, supplemented by instruments in British Columbia, Mexico, Idaho, and Nevada. Algorithms continually listen to this seismic cacophony, speedily determining what is a genuine quake and what is irrelevant natural or artificial noise.
This data is sent to various servers, which in the blink of an eye calculate an earthquake’s approximate characteristics, including its magnitude (the size of the quake) and its intensity (the degree of shaking it will cause along the path of the developing rupture). If a quake meets a certain threshold, then the USGS will generate an imminent incoming quake warning.
This threshold varies. It is a magnitude 4.5 for ShakeAlert-powered cellphone apps and the Android operating system. For the Wireless Emergency Alerts system, a federally managed system that broadcasts a message to all compatible mobile devices, it’s a magnitude 5.0 quake—slightly higher, as such a widespread alert requires a stronger chance of quake-related damage.
“There’s lots and lots of debate as to exactly where those thresholds should be set,” says Harold Tobin, the director of the Pacific Northwest Seismic Network. Some argue for lower values so that people can get used to regular alerts, but others are wary of making it look like they’re crying wolf. “That’s the balance.”
When an imminent earthquake alert is generated, USGS affiliates like cellphone companies who are plugged into to the ShakeAlert data stream will send that alert out to all compatible devices, ideally tens of seconds before the damaging types of seismic waves arrive, giving people time to drop, cover, and hold on until the shaking stops.
There are several pros to this model of quake early warning, the sort that can be found not just in the U.S., but in Mexico, Japan, Taiwan, and other countries. A dense ground-based array of seismometers, algorithms trained on an abundance of real-world data, and a system that is well integrated into public life all contribute to its effectiveness. Alerts can also trigger automated actions, from slowing down trains to shutting off industrial process—the sort of actions that “will have a defining impact on recovery,” says de Groot.
It’s not a panacea, however: People already close to the quake’s origin will get essentially no warning time at all. And if an earthquake begins offshore or deep underground, the warning can only be generated when seismometers first detect it—and seismometers are often located where plenty of people can be found.
Ruptures can also evolve unpredictably. What may start out as a moderate magnitude can escalate dramatically if an earthquake smashes through geological barriers, triggering ruptures on additional faults, explains Zhe Jia, a geophysicist at the Scripps Institution of Oceanography.
Crowdsourcing disaster
Systems like ShakeAlert can work wonders—but not all countries have a fully-fledged seismic ground array to rely on. Google is trying out another model: crowdsourcing seismic data.
All contemporary smartphones, including those that use the company’s Android operating system, have accelerometers that detect motion, including seismic shaking. If enough people in one area experience the onset of a quake, their phones should collectively register that onset and transmit a warning to those further afield.
Google’s Android Earthquake Alerts System uses ground-based seismic arrays where it can (like in California), but the idea here is to provide a life-saving alternative in other parts of the world. “It’s a super interesting and potentially useful and important way of doing early warning,” says Tobin. “We do all carry quite sophisticated sensors around with us every day, and the fact that there are billions of those devices in the world—literally—means that [there will be] enough of them to be parked somewhere stable, at any given moment, to be a reliable detector.”
But Tobin added: “I do have concerns.” The Android earthquake warning system was operating when a pair of remarkably destructive quakes hit both Turkey and Syria in February 2023, killing at least 55,000 people. While alerts were apparently broadcast to millions of people in the afflicted regions, they failed to reach most of them. That failure is surprising: most people in the region own Android-powered phones, and the quake struck at night, when they would be stationary and at their most sensitive to recording seismic waves.
When asked about this, a Google spokesperson told National Geographic via email: “Our system detected and sent alerts for both major earthquakes and many aftershocks in Turkey.” Noting that Google’s alert system is “not designed to replace any official or other public warning systems,” they added that “numerous factors can affect whether users receive, notice, or act on a supplemental alert,” including Internet availability and whether people saw the alerts in the middle of the night.
Why so many people reported that they didn’t receive these alerts, though, remains unclear.
“The concept is really good,” says Tobin—it shows promise, and there is a clear need for this sort of system in areas like Turkey, which has a decent ground-based seismic array but nothing as sophisticated as ShakeAlert. “But it is really important to say that it is not tested technology, really.”
Pushing the frontier
Researchers like Tobin are concerned that people may believe that the cellphone crowdsourcing method is equivalent to the ground-based array model, which it presently isn’t. They are especially worried that cash-strapped or uncharitable governments may come to rely on mobile phones rather than fund and develop their own ShakeAlert-style system.
Both models of earthquake early warning systems are being improved, with ShakeAlert getting a near-continuous stream of software and hardware upgrades. Even at their best, however, they remain “a tool in the toolbox,” says de Groot. Quake-resistant building codes need to be adhered to, and people need to know how to protect themselves in the seconds they may be granted.
Seismology remains a young science. Earthquake early warning and forecasting is “like weather forecasting 100 years ago,” says Jia, and making big leaps in the field “requires a lot of patience.” But that earthquake early warning systems exist at all is testament to how far scientists have come already—and hints at the progress yet to be made.
“We’re always trying to push the frontier,” says de Groot.
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