Using smartphone networks, scientists are testing new low-cost efficient earthquake early warning system for areas with large populations and limited resources.
By Meghomita Das, Department of Earth & Planetary Sciences, McGill University, Montreal, Canada (@meghomita)
Citation: Das, M., 2021, Can smartphones affixed to buildings detect earthquakes?, Temblor, http://doi.org/10.32858/temblor.201
This article is also available in Spanish
Damaging earthquakes can strike at any time, leaving behind a trail of devastation. Recovery from such events can take several years. Unfortunately, scientists cannot forecast the exact time an earthquake will strike. But extensive research in the field of earthquake early warning systems is ongoing. Such systems can provide seconds of warning, which could save lives and prevent people from overwhelming emergency management systems.
Earthquake early warning systems work by having a densely distributed network of seismic stations capable of rapidly detecting an earthquake, and by sending alerts that warn of shaking to the population. A significant hurdle to designing and implementing such systems is the high cost of installing multiple, scientific-grade seismic stations across earthquake-prone regions. For countries like India or Mexico, which have limited resources and high population densities, these expensive networks are not feasible.
In a recent study published in AGU Advances, a team of scientists explored whether a low-cost, robust and operational earthquake early warning system — built around comparatively cheap smartphones instead of seismic stations — might become a reality in the near future in Costa Rica, a country that regularly experiences high-magnitude earthquakes. During a six-month testing period, this network, called Alerta Sismica Temprana Utilizando Telefonos Inteligentes (ASTUTI), a collaborative effort between the U.S. Geological Survey and the Universidad Nacional, Costa Rica, detected and sent alerts for five earthquakes that produced significant shaking in San Jose, Costa Rica’s densely populated capital city.
Smartphones and earthquakes
Smartphones come packaged with GPS location services, constant communication via cell networks, and a device called an accelerometer that helps your phone’s screen rotate as you move it around. The accelerometer can also record any shaking your phone may experience. “Essentially, your phone costs maybe $100 and has all the three components that are there in a scientific grade seismic station, which costs thousands of dollars,” says Marino Protti, a study co-author and a seismologist at the Observatorio Vulcanologico y Sismologico de Costa Rica (Universidad Nacional).
To set up the ASTUTI network, the team deployed 82 Android smartphones, encased in protective boxes, throughout Costa Rica, at an annual cost of $20,000 USD. They installed these smartphones inside buildings, on either the walls or floors of the ground story. The phones are plugged in to AC power supplies.
The accelerometers stream data via cellular networks in real time to the cloud, says Protti. A cloud-based server receives signals from all stations. So, when an earthquake strikes and four sites detect strong ground motion, an alert goes out to people in San Jose, providing between 10 and 30 seconds of warning before the earthquake’s waves arrive, he explains.
San Jose’s location relative to the Middle America Trench — where the Cocos Plate dives beneath the Caribbean Plate — is perfect to test the efficacy of this network because the city is in the Goldilocks position. It’s far enough from the trench such that issuing a timely alert is feasible, but close enough such that the population will feel shaking. The ASTUTI network also issued alerts as soon as events were detected, rather than either waiting for an earthquake to grow larger or trying to define its characteristics. This choice gave people more time to protect themselves.
Did ASTUTI feel it?
During its six months of operation, a group of people selected to receive alerts via phone were notified of five events that ASTUTI detected, with magnitudes ranging between 4.8 and 5.3. Thirteen earthquakes struck Costa Rica in that time, but the other eight earthquakes did not produce significant shaking to warrant an alert. For two of the five detected events, ASTUTI sent out alerts at the earliest possible time — when the first wave from the earthquake, also called the P-wave — was detected by smartphones. This provided people with enough time to take protective action. Moreover, each of the five detected events were accompanied by a “Did You Feel It” report by the U.S. Geological Survey. This citizen science project collects “felt reports” from people who felt shaking (or didn’t) during earthquakes worldwide. In other words, the earthquakes that shook people enough to file a report were detected by the ASTUTI network.
With recent advancements in earthquake early warning, there is a potential for developing a network consisting of expensive high-end devices complemented by a larger number of low-cost devices capable of detecting ground motion, says Raj Prasanna, a telecommunications and electronics engineer and senior lecturer at Massey University-New Zealand who was not involved with this study. “Together, they can become an affordable warning network, with acceptable levels of reliability,” he says.
In the next phase of development, the team plans to create a hybrid system by integrating this smartphone-enabled network with Costa Rica’s existing scientific-grade seismic network, which will improve the accuracy and reduce time of detection of the earthquake early warning system.
What the public wants
Setting up an earthquake early warning system that effectively prompts the public to get to safety is challenging, says Sarah Minson of the USGS, a co-author of the new study. “How do we find out what people want; how do we find out if they are enjoying the system?” she asks. Because earthquake early warning systems are relatively new and people haven’t interacted with them, Minson says, they may not have a personal feel for what works for them. Plus, every country’s needs are different. People’s responses to the same alerts vary depending upon how that specific society culturally reacts to natural hazards.
To that end, the team plans to develop a smartphone-based application. In the future, they will work with the National Commission for Risk Prevention and Emergency Management in Costa Rica to measure how the Costa Rican population perceives earthquake early warning. The goal, says Protti, is to create a more coordinated response plan for earthquakes in Costa Rica. By coupling effective messaging with earthquake early warning, the public will have crucial seconds to take actions that can protect their lives.
References
Brooks, B. A., Protti, M., Ericksen, T., Bunn, J., Vega, F., Cochran, E. S., … & Glennie, C. L. (2021). Robust earthquake early warning at a fraction of the cost: ASTUTI Costa Rica. AGU Advances, 2(3), e2021AV000407.