Seismic damage is a result of wave amplitude and ground acceleration. P-waves are compressional and S-waves are shear, but both travel through the deep crust. By the time energy reaches the surface, it transforms into Love and Rayleigh waves. These waves “trap” energy at the surface. Their long wavelengths and high amplitudes cause the ground to shift both horizontally and vertically simultaneously. Most architectural structures are designed to handle vertical loads (gravity) but are very weak against the intense horizontal “whiplash” motion provided by L waves, making them the primary agents of structural failure and disaster.