What is going on with the Mariners playing an away game in Seattle?

I am going to say this honestly, but until I saw your post I was not away of this happening. I mean first of all could the concerts or the scheduling of the concerts that i would assume in the stadium of the Florida Marlins is where the concerts are being held at. But does this make sense to have the game in Seattle, but then the Seattle Mariners have to be visitors at their stadiums. I know that Wrigley Field has hosted concerts in the ballpark in the past, and even this summer Paul McCartney is scheduled to play 2 concerts at Wrigley Field, on July 31st and August 1st, but on those two dates the Chicago Cubs should be out of town, and the past when concerts been held at Wrigley Field, the Chicago Cubs have been on the road. But for these games won't the DH will be used, since it is an American League Ballpark, but with a National League team hosting. I know in the past 2 teams have played baseball games, in a stadium, that neither team normally plays their home games their, but are there no National League ballparks close to the Florida Marlins that are not available at that time where something could happen that will make more sense.