They need seismic isolation regardless of where they build. Cutting edge fabs require such precision that a poorly shielded USB port can cause enough noise to create problems, let alone the vibrations from distant earthquakes. (Source: previous work with electron microscopes)
Fabs are expensive because every part of building it from the electrical wiring to the seismic isolation to the HVAC system needs to be perfectly tuned to remove all sources of noise. Most of these costs are superlinear if not exponential with the magnitude of noise.
Fabs are expensive because every part of building it from the electrical wiring to the seismic isolation to the HVAC system needs to be perfectly tuned to remove all sources of noise. Most of these costs are superlinear if not exponential with the magnitude of noise.