Earthquake early warning? There’s an app for that…

Earthquake early warning? There’s an app for that…

An app that converts smartphones into makeshift seismometers and could save lives by providing early warning of earthquakes has been successfully demonstrated in Costa Rica.

That’s important, says Esteban Chaves, a seismologist at the Volcanological and Seismological Observatory of Costa Rica, because seismometers cost in the order of $40,000 to $50,000. “A cell phone is $1,000 or less,” he says.

Earthquake early warning isn’t the same thing as earthquake prediction. Prediction is still in its infancy, fraught with unproven theories verging on voodoo. Early warning is proven science. It works by detecting the onset of an earthquake, close to its epicentre, and relaying a warning to people farther away, before the seismic waves reach them. It’s advance notice of approaching shockwaves from an earthquake that has already happened.

Prediction is still in its infancy but early warning is proven science.

Several countries already have seismometer networks dedicated to doing this, including Japan, Taiwan, and parts of the United States. But the leader in the field is Mexico.

In 1985 a magnitude 8.0 earthquake in the Pacific Ocean sent shockwaves 350 kilometres inland, killing at least 5,000 people in Mexico City. Stunned by that tragedy, Mexico responded by installing seismometers along the coast to detect future earthquakes in time to provide its populous capital city with at least a modicum of warning.

Operational now for 29 years, that system has grown to become one of the world’s most effective. On 23 June 2020, when the south-eastern Mexican coast was shaken by a magnitude 7.4 tremblor, the system quickly calculated the severity of the event, predicted what cities were in danger, and rapidly sent out automated warnings.

Oaxaca City got 30 seconds advance notice, said Geraldo Suarez of the Instituto de Geofisica at the National University of Mexico. Mexico City got more than two minutes.

That may not sound like a lot, but it’s enough time for people to stop vehicles, move to safe locations, stop surgeries or other delicate procedures, open firehouse doors, shut down gas lines, and otherwise take whatever measures they can to minimise the upcoming damage, says James Lindsey, a regional sales manager for seismometer manufacturer Güralp Systems Ltd.

It’s even possible to predict what parts of a city are most likely to be severely damaged – before calls for help start coming in.

Earthquakes recorded by the usgs
Earthquakes recorded by the USGS. Credit:

But, as Chaves says, seismometers are expensive. Which brings us back to smartphones.

In a test for how they might be able to do the same thing but much less expensively, a team led by Los Angeles-based Ben Brooks of the US Geological Survey bought 82 Android phones – about the cost of two seismometers. They taped the phones to baseboards, or skirting boards, in buildings along Costa Rica’s Pacific coast, the source of most of the country’s biggest earthquakes. They installed a custom-made earthquake-sensing app on the phones, making sure they had internet access to report whatever tremblors they felt.

It worked. During six months of testing, the system did a good job at detecting earthquakes big enough to produce “noticeable shaking”, defined as roughly magnitude 5.0. Those aren’t big enough to be particularly dangerous, but they are large enough to be easily felt, making them perfect for testing the system.

It’s even possible to predict what parts of a city are most likely to be severely damaged – before calls for help start coming in.

At 51,100 sq. km, Costa Rica is a small enough country that nowhere is sufficiently far inland to get as much warning as Mexico City gets from Mexico’s system (Mexico’s area is nearly 2 million sq. km). But the tests found that that the system provided up to 30 seconds advance notice of an approaching tremor, Brooks says, depending on how far you were from its epicentre.

In simulations, he adds, it appears that the capital city of San José would be able to get 9–13 seconds advance notice of a repeat of Costa Rica’s most recent severe earthquake, a magnitude 7.6 tremor in 2012, near the eastern city of Nicoya.

“Ten seconds is plenty of time to protect a lot of lives,” Chaves says. Especially if, as Brooks puts it, they are taught to “drop, cover, and hold on”.

The next step is to figure out how to ramp up the phones into a functioning real-world system.

“Ten seconds is plenty of time to protect a lot of lives.”

“There are details that need to be ironed out,” Suarez says from his perspective in Mexico. “In particular, I am concerned about how they will solve the timely delivery of alerts to a large number of people once the system is fully operational.”

Part of the process might be via sirens, as are used in some coastal communities for tsunami warnings. Mexico City uses public loudspeakers. But, Suarez says, Mexico’s alerts also go out via WhatsApp, Telegram, email, and other telecom services.

Chaves agrees that this is an issue. “The scientific part is done,” he says. “The main part of the problem is the social part, where we need to communicate that there is an alert.” What will be needed, he says, “is an ongoing effort to make people understand that this is important and can save their lives and their families’ lives.”

Meanwhile, Brooks predicts that other countries will jump on the smartphone-seismometer bandwagon. “The performance is at a level that I imagine would interest even wealthier countries,” he says. “When your objective is warning, you don’t necessarily need the fanciest equipment.”

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