Mexican citizens watching TV on Friday were subject to a loud siren. Just over a minute later, the Guerrero region was hit by a powerful magnitude 7.4 earthquake, which was also felt in the capital.
Mexico employs this type of early warning system (EWS) which uses sensitive equipment to detect low-magnitude tremors which humans cannot feel. The warning can then be distributed via a number of methods – sirens in public spaces, TV, radio and social networks. This event occurred while a news team was broadcasting, as shown in the YouTube video below, where the anchor continues presenting after the sirens start and then, around a minute later, the studio begins to shake with the tremors.
As of yet, there have been no reported deaths due to the earthquake, but some structural damage was caused. Tsunamis can be caused by earthquakes, and this one was centred on the Guerrero region, which is on the south-western coast of Mexico. The threat was quickly confirmed as being low, and no tsunami waves were reported.
NOAA (National Oceanographic and Atmospheric Administration) can give warning messages for each potential tsunami threat, detailing the recommended response for governments and the threat level. This one was given for the Mexican Earthquake, sent to Hawaii as a precaution:
000 WEHW42 PHEB 181440 TIBHWX HIZ001>003-005>009-012>014-016>021-023>026-181640- TSUNAMI INFORMATION STATEMENT NUMBER 1 NWS PACIFIC TSUNAMI WARNING CENTER EWA BEACH HI 440 AM HST FRI APR 18 2014 TO - CIVIL DEFENSE IN THE STATE OF HAWAII SUBJECT - TSUNAMI INFORMATION STATEMENT THIS STATEMENT IS FOR INFORMATION ONLY. NO ACTION REQUIRED. AN EARTHQUAKE HAS OCCURRED WITH THESE PRELIMINARY PARAMETERS ORIGIN TIME - 0427 AM HST 18 APR 2014 COORDINATES - 17.6 NORTH 100.9 WEST LOCATION - NEAR THE COAST OF GUERRERO MEXICO MAGNITUDE - 7.4 MOMENT EVALUATION BASED ON ALL AVAILABLE DATA A DESTRUCTIVE PACIFIC-WIDE TSUNAMI IS NOT EXPECTED AND THERE IS NO TSUNAMI THREAT TO HAWAII. REPEAT. A DESTRUCTIVE PACIFIC-WIDE TSUNAMI IS NOT EXPECTED AND THERE IS NO TSUNAMI THREAT TO HAWAII. THIS WILL BE THE ONLY STATEMENT ISSUED FOR THIS EVENT UNLESS ADDITIONAL DATA ARE RECEIVED. $$
However, without proper education on what to do in the event of a disaster, EWS can be useless and may instead cause panic. Education will normally inform people about the evacuation protocols – where to go and what your priorities should be. Government-issued leaflets and signage can be used, though in some countries they will also educate children at school, most notably in Japan.