This thesis presents the results of traveltime inversion of seismic wide-angle reflection/refraction data for strongly varying media. The two-dimensional velocity structure along two lines across the central Chilean margin (near Valparaiso) has been obtained and assessed in terms of resolution, uncertainties, and non-uniqueness. The traveltime inversion method was used to model the data and assess the model reliability. A tomographic approach was used to assess the objectivity of the structures in the final models. The final models include slope sediments, the Valparaiso forearc basin, subducting sediments, an accretionary wedge, upper and lower continental crust, a two-layer oceanic crust, and uppermost mantle. The thesis results were compared with the results of forward modeling of the same dataset and with results of analogous seismic surveys across convergent margins worldwide.