i saw this effect and would like to know how to do it in illustrator
This would be easier to do in Photoshop, which is how I suspect it was actually created.
Make a pattern from squares filled with a radial gradient like this, and save the PSD where you can easily find it. In this example I named the file FresnelTexture, because that's what it kind of reminds me of.
Next, fill a layer with black, use the Elliptical select tool to make a circle and fill it blue. Then Select > Deselect.
Finally do Filter > Distort > Glass, and load the texture PSD, tweak the settings until you are happy with the effect.
From here you could import the raster image into Illustrator and auto trace it. Technically, you could probably do this in Illustrator too, since it has the same Glass filter, but the result will be raster and you'd still have to auto trace it if you want vectors.
The effect works on other images too, such as photographs