1. A method for generating an image of earth formations penetrated by a wellbore, comprising: generating an initial model of the earth formations using formation resistivity measured by a direct current signal; calculating a response to the initial model of an instrument used to make the direct current resistivity measurements; comparing the calculated response to the measurements of resistivity; adjusting the model and repeating the calculating and comparing until a difference between the calculated response and measurements reaches a minimum; refining the adjusted model based on resistivity measurements made using an electromagnetic measuring instrument; and constraining the refined model using acoustic measurement parameters.