1990 Toyota Corolla GAS LEAK

I noticed a puddle of gasoline under the trunk of my car. I was parked on an incline with the front facing up. When parking on level ground it doesn't seem to leak.

Is the gas tank perhaps rotted somewhere? I don't know where the tank is located There's a lot of snow on the ground now which makes it difficult to get underneath. Is it possible that it's the gas line?

Thanks for any help you can give me.