The Seismic Early Warning System of Mexico (SASMEX): A Retrospective View and Future Challenges

Abstract

The earthquake early warning system of Mexico, SASMEX, has 30 years of uninterrupted and successful operation. During this time, the system recorded ∼9,800 earthquakes and broadcast 111 alerts. Alerting was simplified recently, avoiding the emission of two types of alerts. Only earthquakes above a magnitude threshold, dependent on distance to the target city are alerted. SASMEX disseminates early warnings using dedicated receivers, public loudspeakers, multi-hazard radios, and participating TV and radio stations. It is estimated that ∼25 million people receive alert messages from SASMEX. Cell-broadcasting messaging, necessary for the timely delivery of alerts, is not implemented by the local cellular phone operators. The addition of cell phone communication would increase the number of users benefitting from the system. SASMEX does not publish ground motion predictions at the time of issuing the alert. Instead, it distributes a map of peak ground acceleration in Mexico City ∼1 minute after the arrival of strong motion, via electronic messaging. The accepted practice for the population in general is to evacuate at the sound of the alert. This is useful in schools and low-rise buildings, where people are generally drilled to evacuate rapidly. It is not effective in high-rise buildings and where large numbers of people concentrate. Finding protection and not trying to evacuate may be a better option, as it is recommended by other seismic early warning systems. The damaging 19 September 2017 earthquake underlined the difficulties of alerting earthquakes at close distances. Using a different sound of the alert or a countdown may be advisable, so people understand they have less time than normally assumed. There are few social studies on the use of the alert. It is suggested to conduct these studies to explore better ways to use and communicate the seismic alert, including automatic processes to shut down hazardous facilities.

Earthquake Early Warning in Central America: The Societal Perspective

“…In contrast to ShakeAlert and JMA, SASMEX does not deliver alerts based on the expected felt intensity. Instead, SASMEX sends a single alert to cities based on a combined criterion of epicentral distance and moment magnitude (M5+ and D < 250 km, M5.5+ and D < 350 km; and M6+ and D ≥ 350 km) [59,66].…”

“…The dissemination of EEW alerts requires data transmission and communication infrastructure to be fast and robust so the public receives alerts promptly and reliably [66]. Most public EEW systems use a multi-channel strategy to disseminate alerts.…”

“…SASMEX issues alerts through 12,600 loudspeakers, dedicated receivers, TV and radio station partners. However, cell-broadcast messaging is not available because mobile providers do not offer this service yet [66]. Participants in New Zealand, Switzerland, and Central America prefer to have redundancy and not rely solely on one technology.…”

Integrating earthquake early warnings into business continuity and organisational resilience: lessons learned from Mexico City

“…When the EEW system instead provided no warning, this led to confusion and affected trust. This circumstance highlighted the challenges involved in warning of an earthquake at close range (Suárez, 2022). Santos‐Reyes (2019) underscored the critical need for further governance development, particularly in terms of training and the procedures to follow before, during, and after an earthquake (see also Suarez, Novelo, and Mansilla, 2009).…”

“…In the following sections, an empirical analysis of the case study context of Mexico City, Mexico, is presented, bridging the social science and the technical fields. Here, the authorities have developed an operational EEW system that needs to improve its level of effectiveness (Suarez, Novelo, and Mansilla, 2009; Santos‐Reyes, 2019; Suárez, 2022). A mixed methods approach is developed to derive qualitative and quantitative evidence discussed within academic literature and practical considerations of the International Organization for Standardization's standards (ISO, 2019).…”