This alarm comes from Mexico City's public earthquake early-warning system, which broadcasts warnings through loudspeakers across the city when sensors detect strong shaking elsewhere. The distinctive tone and spoken alert are designed to be recognised instantly, even outdoors, and give residents a short window to take cover. Clips of the sound spread online through news footage and videos recorded during real alerts, and creators later reused it as shorthand for impending disaster, panic or a bad decision about to land.