Tornadoes and floods so for this year have reinforced the need to be prepared and self-sufficient. I listen to scanners across the country during disasters. Often, I go back and listen to archives to see how events played out. Absolute chaos is the best way to describe what I normally hear.
There is no reason to think southeast Missouri would be any different. There is very little radio interoperability between communities which would compound the problem when other agencies respond to help.
The standard is to be prepared for 72 hours. FEMA says areas of SEMO should expect 96 hours before an organized response would arrive after a 7.2 magnitude or larger earthquake.