Tagged: SAME

Decoding the Mexican Seismic Alert System (SASMEX Alerta sísmica)

Back in 2015 we posted about the dsame software, which is a decoder for the American Emergency Alert System (EAS) which is encoded with the SAME (Specific Area Message Encoding) protocol. EAS transmits on the NOAA weather frequency. 

Recently programmer Sam submitted news about his fork of dsame which adds the ability to decode the Mexican SASMEX (Sistema de Alerta Sísmica Mexicano) alert system. SASMEX is a system developed by the Mexican Government which can detect earthquakes and rapidly activate a warning siren across the country, allowing an early warning for people to prepare for an incoming earthquake.

The sirens appear to be activated wirelessly through the same frequencies that weather and EAS use, and so the signal can be monitored with an RTL-SDR or other SDR. When an active signal is present, the forked dsame software will decode the alert. The alert could then be used to activate a local siren or display.

How the SASMEX System Works (Credit: http://www.cires.org.mx/sasmex_n.php)

New EAS SAME Weather Alert Decoder

Over on Reddit and GitHub user cuppa-joe has released a Python based EAS SAME Alert message decoder called dsame which is compatible with the RTL-SDR. EAS is an acronym for Emergency Alert System and is a system that is most commonly used to alert the public to local weather emergencies such as tornadoes, flash floods and severe thunderstorms.

Local EAS weather alerts are encoded with the SAME (Specific Area Message Encoding) protocol. They are transmitted on the local weather radio frequency in the USA and Canada and some weather radio’s are capable of decoding the EAS SAME data. Cuppa-joe’s dsame EAS decoder outputs full EAS weather messages such as:

The National Weather Service in Pleasant Hill, Missouri has issued a Required Weekly Test valid until 12:30 PM for the following counties in Kansas: Leavenworth, Wyandotte, Johnson, Miami, and for the following counties in Missouri: Clay, Platte, Jackson, Cass. (KEAX/NWS)

To use the software you will still need to use a EAS demodulator such as multimon-ng which is available for Windows and Linux, and you will also need Python 2.7+ installed.

An example EAS SAME alert can be heard in the player below: