Reacción a "Android earthquake early warning system proves effective on smartphones"

Earthquake Early Warning Systems (EEWS) are designed to generate alerts when a destructive earthquake occurs. They make use of the time interval between the detection of the first few seconds of seismic wave arrivals at a station near the epicentre and the arrival of the more destructive waves at a more distant location, which allows for damage prevention and mitigation. An EEWS can locate an earthquake and calculate its size—either moment magnitude (Mw) or local magnitude (ML)—using only the beginning of the seismogram. This concept should not be confused with that of an Earthquake Alert, where information about the earthquake’s location and magnitude is sent after it has occurred. On 14 July 2025, after a magnitude 5.3 earthquake occurred southeast of Cabo de Gata (Spain), an Earthquake Alert was issued.

The article by Allen et al. (2025) presents a new tool for Earthquake Early Warning Systems, consisting of the global use of Android smart phones (Android Earthquake Alert, AEA) to detect earthquakes. Therefore, this new EEWS system provides coverage in areas lacking seismic infrastructure and reaches 2.5 billion people—an unprecedented scale. Traditionally, EEWS rely on regional seismic networks to generate alerts. The denser the network, the faster and more accurately the earthquake’s location and magnitude (Mw or ML) can be determined. When this magnitude exceeds a certain threshold—typically between 4.5 and 5.0—an alert is issued. Thus, delays in calculating the magnitude also delay alerts to users. Increasing the density of a seismic network entails significant financial cost and is not always feasible. The innovation of the AEA lies in the fact that smart phones are equipped with accelerometers that record ground acceleration during an earthquake, thereby increasing the availability of seismic instrumentation.

The authors have long been working on this subject, in regions such as New Zealand, Greece (2021), Turkey, and the Philippines (2022). Allen is a pioneer in EEWS development, having created the ShakeAlert system for early earthquake warnings in California. The first EEWS were installed in 1991 in Mexico and in 2007 in Japan, followed later by Taiwan, South Korea, and the United States. It is estimated that currently 250 million people have access to an EEWS. By including AEAs, this coverage expands to 2.5 billion people. Alerts from EEWS and AEAs are similar in their magnitude estimations and margins of error.

One of the limitations of EEWS—and, by extension, AEAs—are larger earthquakes, with magnitudes of 7.5 and above. In many of these cases, the rupture is complex and consists of multiple events, making it difficult to accurately estimate the magnitude and issue timely alerts. This was the case with the 2023 earthquakes in Turkey (magnitudes 7.8 and 7.5). To address this challenge, the authors developed a new algorithm capable of estimating a magnitude of 7.4 just 24 seconds after the earthquake began. Other limitations of the system include accuracy, which depends on the density of available smart phones and the level of ambient noise. Delays in magnitude estimation and false positives—caused, for example, by storms or massive vibrations—can also occur, although these have been progressively reduced through algorithmic improvements.

The authors emphasize that, for alerts to be truly effective, it is essential for the public to be educated in advance on how to act during an earthquake and to know basic self-protection measures. Among the main obstacles to implementing this system are institutional acceptance, integration with national alert systems, potential privacy concerns, and the need for educational campaigns to ensure an appropriate response from the public.

In Spain, in 2010, the Complutense University of Madrid (UCM), together with the Royal Institute and Observatory of the Navy and the Geological Institute of Catalonia, conducted studies on the feasibility of an earthquake early warning system in the southern part of the country. In 2015, the first operational EEWS—called PRESTo—was installed in the Department of Earth Physics and Astrophysics at the UCM Faculty of Physical Sciences, in collaboration with the University of Naples Federico II. More recently, in 2024, the same department launched Quake-Up, an updated version of that system. Additionally, just a few days ago, the Community of Madrid awarded a predoctoral contract to Prof. Mattesini as part of the 2024 call for research training grants. This contract will fund a doctoral thesis focused on improving the efficiency of EEWS in Spain.

Currently, Spain has two EEWS systems operating at the research level. However, as previously mentioned, it will be up to society itself to demand their effective implementation and widespread use.