We use the Godano et al. (2022) method for the evaluation of the b maps on the faults of the largest earthquakes (M ≥ 7.0) occurred in California. The method allows an in- dependent evaluation of the Gutenberg-Richter b parameter avoiding the overlap of the cells and the missing of some earthquake keeping all the available information in the cat- alogue. In the present study, we analyzed four large earthquakes: Landers, Hector Mine, Baja California and Searless Valley, for which consolidated and detailed fault geometries are available. The obtained maps confirm that the b value can be considered as a strain- meter and allow us to enlighten the presence of barriers, namely strong patches of the fault plane that are resistive to breaking, on the fault of the analyzed earthquakes. We report as a further estimated parameter the time window during which aftershocks oc- cur in cell, ∆t. This quantity is very useful in a better definition of the aftershocks gen- eration mechanism. Infact, it reveals where the stress is released in a short time inter- val, how the complexity of the faulting process controls the occurrence of aftershocks on the fault and the duration of the whole sequences.

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