"Thump" sound is unusual, is it outgoing artillery?
I haven't looked at any maps for a while, How far is it from the green zone to Sadr city?
When we hear explosions that happen in our "neighborhood," I can distinguish between incoming and outgoing and usually even tell what it is - mortars, rockets, car bombs, etc. They all have their distinctive sounds, and when they're close up, they all have the ability to get my heart racing pretty good. LOL
While Sadr City is called "on the outskirts," it is not that far from the center of town where the GZ is. I'd say it's about 5 miles away. If that.