Significant intraplate earthquakes have been observed under deep oceans and in all continents except Greenland. They present special problems of seismic risk estimation compared to the more frequent interplate earthquakes. Their location in space and time is more uncertain because of the low seismicity rate, scattered locations, and lack of surface seismogenic fault evidence. Nevertheless, recent geological and seismological work in several stable continents, particularly western North America and Australia, has improved the assessment of seismic hazard maps and risk zonation in such regions. Estimation of robust synthetic ground motion spectra and time histories, however, remains relatively uncertain. Strong motion instrumentation at Continental Reference Stations (CRS) is recommended.