You are able to sense invisible creatures and power surges. You may also use the 'stamp' command to actively locate other creatures around you (this shows the location of up to 1 creature per 10 ranks, listed in order of proximity).
Your detect level (for seeing invisible creatures) increases by +1 per rank.
A power surge occurs when a player enters the Nexus, or when something dies.
The optimal range of your Tremor Sense is 500 feet, plus 25 feet per rank, plus 5 feet per daily kill the target has made, minus 25 feet per rank the target has in Cloak of Shadows. If the target is flying, this range is then halved. The range is then increased by a further 5 feet per point of Size the target has (or 10 feet per point if they are moving). You can also sense the distance of targets at up to three times this range, but not their direction as well.