As I undertand monitoring is a permanent activity, sometimes it is even automatic. Auditing happens during an specific period of time and has very specific objectives. I think that this study might help you!
Strausz, R. (2006). Timing of verification procedures: Monitoring versus auditing. Journal of Economic Behavior & Organization, 59(1), 89-107.
Structural Health Monitoring. Structural health monitoring (SHM) refers to the process of implementing a damage detection ... Commonly known as Structural Health Assessment (SHA) or SHM.
Structural Health Assessment = the systematic evaluation of the adequacy of damage detection and implementation structures within the system
Monitoring = continuously observing events to look for outliers, against set frame(s). Auditing = reviewing and verifying the event, results or assertion by an entity to assure that such observed events, results or assertions present fairly, in all material respects, according to the agreed or stautory standard or expected value.