Moles dig tunnels underground. So if you have cave-ins as you step on parts of your yard, moles are probably the issue. I know you can buy mole traps. They are larger than mouse traps. You insert them into the tunnels. As far as something topical, I'm not for sure. But, if the problem doesn't go away within a week or so, I would call someone so that your whole yard isn't taken over.
Just curious. Try googling mole repellants, there may be some sort of spice or mixture that would get rid of them. I'll check too.