Question

Please explain it to me, what is the grammar construction "to being caught"

The whole sentence is: The magnitude 4.4 earthquake that struck near Westwood early Monday was a "rude awakening" for Angelenos who remain vulnerable to being caught unprepared by a major temblor, Mayor Eric Garcetti said.

Thank you in advance!
 

Answer 1

being caught is a passive stucture, e.g. I am caught in the act.

vulnerable + to being caught is similar to "be used to + Ving", as in the subject is vulnerable to somethING, here being caught, that is the state of being caught.