Animating arcs waves With I could create an animation using arcs in After Effects as the example of the link below.

Animation

I'm trying to animate only the region where the arcs are opening.

In After Effects I can not create arcs. My attempts were only with circles.
I think you can achieve this effect using the built in Radio Waves effect.

https://helpx.adobe.com/after-effects/using/generate-effects.html

I think you can restrict the arc size.  If you can't, you could always mask the areas of the circle you don't want to see.