Normally the pile foundation receive lateral excitation on pile head based on two effect, the one is inertial forces due to super structural load influence and another kind of force is due to kinematic forces due to liquefaction. Professor. Gopal Madabhushi from university of Cambridge, UK..I suggest you to read the book i.e. Piles in liquefiable soil authored by Gopal Madabhushi for your reference.. you will get complete information about the piles under earthquake loading..