Smartphones Enabled Up to 58 Seconds Strong-Shaking Warning in the M7.8 Türkiye Earthquake

Introduction

Public earthquake early warning systems (PEEWSs) hold the promise of saving lives by providing advance notice of seismic waves, potentially offering seconds to tens of seconds of warning time. This capability is particularly critical for destructive, large-magnitude earthquakes. The devastating M7.8 Pazarcik earthquake in Türkiye on February 6, 2023, which tragically claimed nearly 60,000 lives, highlights the immense challenge and importance of such systems. Warning people of imminent strong shaking during a massive earthquake is inherently difficult because the alert must be issued before the earthquake has reached its full intensity. A recent study published in Scientific Reports investigates the performance of a smartphone-based PEEWS during this catastrophic event, revealing its potential to deliver valuable warning times.

Smartphone-Based Early Warning System Performance

The study focused on the Earthquake Network (EQN), an operational smartphone-based PEEWS that was reportedly the only one active during the Pazarcik earthquake. EQN operates by utilizing smartphones that are charging, where the app analyzes the device's acceleration in real-time to detect significant shaking. When shaking is detected, the app sends the peak acceleration and the smartphone's coordinates to the EQN server. The server then analyzes these data to estimate the earthquake's magnitude and determine warning distances for different levels of shaking. Users receive personalized alerts with a countdown to the anticipated arrival of seismic waves and the expected ground-shaking intensity.

Alerting Strategy and Warning Times

The EQN system detected the Pazarcik earthquake approximately 12 seconds after the rupture began. This detection was based on data from 53 smartphones within 100 km of the epicenter. Following detection, the EQN issued alerts to its users. For those within a 141 km radius of the estimated epicenter, a warning for strong ground shaking was sent. Users further out, between 141 km and 412 km, received warnings for moderate shaking, and those even farther received warnings for mild shaking, extending up to thousands of kilometers. Notably, the system's ability to issue alerts across national borders was a key feature.

The study analyzed the warning times provided by EQN by comparing the alert issuance time with the onset of strong ground shaking, defined as a peak ground acceleration (PGA) exceeding 12%g, which corresponds to a Modified Mercalli Intensity of VI. This threshold was chosen as it allows individuals to take protective measures. Waveform data from Turkish seismic stations were used to estimate the spatial distribution of warning times. The analysis revealed that EQN users exposed to strong ground shaking received warning times of up to 58 seconds before the onset of intense shaking.

Potential Impact on the Population

Beyond the actual users of the EQN app, the researchers also estimated the potential warning times for the broader Turkish and Syrian population exposed to similar levels of shaking. By assuming that a strong ground-shaking alert could have been extended to all individuals within the 141 km radius, the study found that approximately 2.7 million people exposed to life-threatening earthquake shaking could have received warnings ranging from 30 to 66 seconds in advance. For those exposed to intensity IX and above, a critical level associated with significant damage and fatalities, warning times of up to 58 seconds were calculated. This extended warning time, even for a massive earthquake, is considered sufficiently long for people to take protective actions.

Conclusion

The M7.8 Pazarcik earthquake provided a critical real-world test for smartphone-based earthquake early warning systems. The EQN system demonstrated its capability to detect a large-magnitude earthquake and issue alerts, providing valuable warning times to its users. The findings suggest that such systems, even with their inherent limitations in precisely estimating earthquake size in real-time, can offer crucial seconds of advance notice. This advance warning, coupled with preparedness and risk awareness, can significantly contribute to mitigating casualties and damage during major seismic events. The study underscores the growing potential of crowdsourced technologies in enhancing public safety in the face of natural disasters.

Original source: "https://www.nature.com/articles/s41598-024-55279-z"