At its most basic level, an action scene is an expression of plot or character development through violence.
Wait, violence? Is that really necessary?
In a word, yes. We’re still essentially the same cantankerous hominids we were a hundred thousand years ago. Ever since the first proto-human got angry about something done by one of his neighbors and picked up a rock to bash the other fellow’s head in, we’ve been solving our disagreements through violent acts. And over the millenia, we’ve gotten very, very good at it.
We may use the trappings of civilization to try to curb our instinctive violent cores, but in the long run, virtually anyone is capable of committing violence at some level. Because of that, action scenes in media play to our low brains. Perhaps it’s some kind of Jungian racial memory, but when we observe others in action, it gives us a kind of catharsis we haven’t been able to obtain socially for thousands of years. That’s why an action scene has to be every bit as important and planned out as a dramatic conversation, an erotic encounter, or a beautiful description. Readers crave that kind of feeling, and it’s up to you to provide it.
Can an action scene be nonviolent?
Sorry, pacifists. No, it cannot. Because action scenes are defined by some level of violence, you cannot have a nonviolent action scene. Scenes without violence are driven forward by other impetuses, such as dialogue or emotional content. Sooner or later, though, a character will choose to take action which is counter to the goals of another character, and that will beget violence.
Your best bet is to make sure it’s a good scene.