A three-dimensional fluid-filled crack model recently developed by Chouet is used to reproduce and explain the spectral characteristics of different classes of long-period events recorded during a hydrofracture experiment conducted at Fenton Hill, New Mexico. We study the dependence on the model parameters of the far-field P-wave radiation due to the vibration of the fluid-filled crack. Those parameters are given by the properties of the fluid and solid, the crack dimensions, the area and location of the crack surface over which the excess pressure is applied, the time history of this excess pressure, and the station location. In this model, the resonance of the crack is sustained by a very slow and dispersive wave called ''crack wave''. The phase velocity of the crack wave depends critically on the impedance contrast between fluid and solid and on the crack dimensions. We are able to fit the dominant features of the Fenton Hill data in the time and frequency domains and draw inferences on the impedance contrast between the fluid and solid. The various classes of events observed can be modeled by a single crack over which the geometry of the applied excess pressure changes. The length, width, and thickness of the crack are estimated to be on the order of 3m, 1m, and 3mm, respectively. The observed spectral roll-off can be explained by a ramp function time dependence of the pressure transient. The rise time necessary to simulate the observed data varies between 2 and 4 ms, depending on the event considered. Assuming the source-receiver distance of 700 m, the amplitude of displacement of the data agree with the model's prediction if the excess pressure applied on the crack is on the order of 20 bars. ¿American Geophysical Union 1990