The Seismic Alert System in Mexico City and the School Prevention Program

Abstract

The Seismic Alert System (SAS) is a public service developed with thesponsorship of the City Government Authorities, with the aim to mitigateseismic disasters. Since August, 1991, after 84 months of continuousoperation, the SAS has been able to detect 681 seismic events in theGuerrero Coast; 12 of them so strong as to trigger general alerts inMexico City, 33 restricted, and one false general alert. The warningranges strong or restricted correspond to seismic magnitude forecastedgreat than 6, or great than 5. During the ``Copala{''} M7.3 earthquake,on September 14, 1995 the SAS was activated and issued a general warningsignal in Mexico City, 72 seconds prior to the first arrival of ``S{''}ground motion. This earthquake warning reached an estimated populationof more than 4 million citizens. The response of children in schools wasmassive due to the application of an earthquake hazard reductionprogram. The Copala earthquake helped us to identify strengths andweaknesses of societal response to the earthquake early warning signal.The long-term plan of hazard mitigation of the National Ministry ofPublic Education, Secretaria de Educacion Publica (SEP), has created anearthquake awareness in the children of various school levels. Eventhough the children did not suffered the disastrous consequences of the1985 earthquake, they are today more aware than the average person wholived through that disastrous event and who is still not trained.