1. A method for monitoring wear in a mechanical system, comprising: (a) repeatedly measuring a parameter over time during operation of the mechanical system; (b) calculating residuals at time points over the life of the mechanical system using an empirical model that models values of said parameter as a function of values of other parameters, said residuals representing the respective differences between each measurement of said parameter and each corresponding parameter value predicted by the empirical model; (c) determining whether the measurements evolve as expected under a time evolution model that relates predictions of residuals over time; and (d) flagging an event in response to the measurements of said parameter deviating over time from the behavior predicted by the time evolution model by more than a threshold value, wherein in accordance with said time evolution model, wear at time t equals the wear at a previous time (t−1) plus a local growth rate at time (t−1).