Highlight the layer in question. Hit the "uu" key -- that's "u" twice in quick succession. You'll reveal all the modified properties. Look for the keyframes. Get to know what's going on with th keyframes. Play with them and their values, and maybe make some more.
Thanks for your response. I meant to add this to my original post, but there aren't any keyframes indicating where the effect starts and stops. The effect is applied to the layer for the entire duration of the composition.
Many of those text presets are actually using expressions to drive the animation, which is the case here. If you're new to AE, those will likely get scary pretty fast.
Conveniently, this preset came along with a few expression sliders that give you easy control over the effect. In your Effect Controls panel (or by twirling open the layer until you see them), you have sliders that let you keyframe the "Frequency" and "Magnitude."
Tweak until you get what you're after.