SLAC-PUB-8487 Ground Motion Models for Future Linear Colliders Work supported by Department of Energy contract DE–AC03–76SF00515. June 2000 Contributed to the 7th European Particle Accelerator Conferences (EPAC 2000) , 6/26/2000—6/30/2000, Vienna, Austria Andrei Seryi Stanford Linear Accelerator Center, Stanford University, Stanford, CA 94309