At its core, avert (verb) means to turn away or to prevent something unpleasant or dangerous from happening [5.3, 5.6]. It originates from Latin roots meaning "to turn away from" [5.3]. Two Distinct Usages To Prevent or Ward Off (Unpleasant Events):

implies a direct, active effort to stop a specific, impending negative outcome [5.2, 5.3].

While often used interchangeably, there is a nuance:

This implies active effort to stop a disaster, tragedy, or crisis [5.2, 5.5].