While applying FWI to broadband data has recently become feasible thanks to increasing computational resources and progresses in the FWI workflow, such applications tend to focus on the reconstruction of high resolution reflectivity images derived from the acoustic impedance. This makes it possible to bypass the migration stage, simplifying nicely the inversion workflow in a single stage of FWI, and thus reducing the processing time from acquisition to interpretation. However, we think that the potential of broadband FWI goes, beyond building high resolution reflectivity images, towards a quantitative characterization of the subsurface mechanical parameters. In this work, we try to assess on a 3D OBC data from the North Sea how increasing the frequency content of the inverted data helps to control the reconstruction of the density and the quality factor, on top of the velocity. The results we obtain are promising: the reconstructed density fit nicely an available density log down to 2 km depth, while the quality factor is shown to help fit waves which are attenuated when crossing the low-velocity zone at the center of the model.