High‐frequency acceleration pulses recorded during recent damaging earthquakes show that the evolution of pore water pressure in liquefiable soils may have a significant effect on earthquake ground motions. Such observations suggest that advanced constitutive soil models capable of treating the phase transformation behavior of liquefiable soils should be used for reliable predictions of earthquake site response. Advanced constitutive models require knowledge of the dilatancy parameters that describe the potential of soils to generate excess pore water pressure. We demonstrate that these dilatancy parameters can be determined directly from field observations by inverting strong motions recorded on vertical arrays (i.e., installation of surface and borehole accelerometers). We analyze the records of the 1987 M 6.6 Superstition Hills earthquake, the 1993 M 7.8 Kushiro‐Oki, Japan, earthquake, and the 2011 M 9.0 Tohoku, Japan, earthquake to quantify the dilatancy parameters at the Wildlife liquefaction array (WLA), at Kushiro port (KP), and the KiK‐net site FKSH14, respectively. Synthetic acceleration time series obtained from the minimum misfit models are describing the time and frequency evolution of the observations more precisely than previously published models. Dilatancy parameters obtained for WLA and KP suggest that soils at these sites were more resistant to liquefaction than predicted from field and laboratory tests. We also infer a high liquefaction resistance (CRR7.5=0.5) for the site FKSH14, which exhibited dilation pulses of up to during the Tohoku earthquake. These findings indicate that even soils with a strong liquefaction resistance may exhibit cyclic mobility effects during strong and prolonged ground motions.