The Mexican Seismic Alert System is the earthquake warning system covering portions of central and southern Mexico. It currently provides up to 60 seconds' warning of earthquakes to Mexico City, Acapulco, Chilpancingo, Morelia, Puebla City, Oaxaca City, Guadalajara, Colima and Toluca. SASMEX is administered by a non-profit civil association, Center for Seismic Instrumentation and Registry . The SASMEX sensor network serving Mexico City has been regarded as the first earthquake early warning system issuing alerts available to the public. SASMEX supplies regular information of all kinds, including reports of earthquakes of all magnitudes, and drills, via Twitter, under the name AlertaSísmica SASMEX. All earthquakes are reported as #TenemosSismo ; warnings of serious ones are delivered as #AlertaSismica.

An earthquake warning system or earthquake alarm system is a system of accelerometers, seismometers, communication, computers, and alarms that is devised for rapidly notifying adjoining regions of a substantial earthquake once one begins. This is not the same as earthquake prediction, which is currently not capable of producing decisive event warnings.