Since this has come up, I am hoping to get some manner of official response, but I also know this is likely to fall into 'DM call', but I shall try none the less.
Tremorsense (Ex)
A creature with tremorsense is sensitive to vibrations in the ground and can automatically pinpoint the location of anything that is in contact with the ground. Aquatic creatures with tremorsense can also sense the location of creatures moving through water. The ability’s range is specified in the creature’s descriptive text.
Now, the questions:
1: Does a creature with tremorsense have the ability to know what the local area around it is like? Examples: 'There are stairs here. There is a lamppost here. There is a table here. There are utensils on the table here. The floor goes up/down.'
2: Does a creature using tremorsense know if there are open spaces underground within its range? Would it notice a pocket of air or water or lava or whatnot in the ground? Would it notice a chest, or a corpse? Tree roots?
3: Would it notice secret tunnels or passages because the space behind those doors is open, but covered up by the wall/bookshelf?
4: Would it be able to figure out the way a maze turns within its range by noting when there is open space and when there is not?
Or are earth elementals and other such entities basically completely blind while burrowing and only able to detect creatures on the surface?