Resolution tests revisited: The power of random numbers

We propose a simple method where the inversion of synthetic data, corresponding to a zeromean random input vector, is used to infer the average horizontal and vertical resolution lengths of tomographic models. The method works well if the resolution operator has a diagonally dominant structure. This assumption, although often verified in seismic tomography, can be tested by simply cross-correlating the input with the output of the synthetic simulation. The method is as efficient as a single checkerboard test, but reveals more easily interpretable information