Instructions:
- Open up your text message app.
- Go to "Menu" -> "Settings". You need to be at the home screen of your text messages. If you are in a particular text message conversation screen, the "Menu" button won't show you the "Settings".
- There should be an "Emergency Alerts" category/option, where you can check off the severity of alerts you want to receive. One alert, "Presidential Alert" can't be disabled.
I believe that my text message app is part of HTC Sense 4.0. I can't be certain that other Android phones don't have a slightly different setup. Either way, I'm fairly certain that, in Android Ice Cream Sandwich 4.0, the option to modify/enable/disable "Emergency Alerts" is going to be in your main text message settings.