I’m from New Irleans and can attest to the sounds. I’m always inside when it happens so I cannot speak of a source, air or ground. But I have heard them. Loud. Shakes the house a little.
As for the “sudden ground thaw”, no. This is New Orleans. There’s no ground freezing. It’s barely been under 50 this winter and I have the A/C on since yesterday. There are sulphur mines in the area.