1. A method of modeling a geological-time function indicating approximate times when subsurface particles were originally deposited, the method being executed by a processor according to software instructions, the method comprising: using the processor: generating a plurality of linear equations of the geological-time function representing a plurality of respective geological properties at each of a plurality of model locations, wherein one of the plurality of geological properties provides fault type information represented by a linear equation defining the geological-time function for a first and a second collocated points, the first point on a negative side of a fault and the second point on a positive side of the fault, wherein the linear equation includes an inequality that specifies that the geological-time function at the second point is greater than the geological-time function at the first point if the fault is a normal fault and the geological-time function at the second point is less than the geological-time function at the first point if the fault is a reverse fault; solving the plurality of linear equations for the geological-time function to simultaneously apply independent data corresponding to the plurality of geological properties into the geological-time function; and modeling the geological-time function.