Mexico City has made changes to its emergency announcement service known as 911 CDMX. The service now sends messages to people’s smartphones warning them of earthquakes. The changes come after a magnitude 7.1 earthquake hit Mexico’s capital on September 19. The quake killed 369 people and caused 38 buildings to collapse. Officials announced the new smartphone program last week. Mayor Miguel Angel Mancera said users of the free 911 CDMX program will receive messages for any earthquake strong enough to damage the city. The program will send sound messages and cause the smartphone to vibrate.