Spatial mapping of Gutenberg-Richters b-value

The code features the implementation of the sampling methods and synthetic tests used in [Kamer, Y. (2014), Comment on "Systematic survey of high-resolution b value imaging along Californian faults: Inference on asperities", JGR. Solid Earth, 119, doi:10.1002/2014JB011147.]
The submission also includes Parkield seismicty as a sample data set.

ATTENTION: If you plan to use this code on real earthquake data, please consider the conclusions from the Parkfield synthetics:

"...the emergence of high and low b value anomalies is a mere artifact of under sampling. These artifacts lead to differences of up to 2 orders of magnitude in the recurrence times; thus, it would be precarious to use such maps for assessment of probabilistic seismic hazard on faults. Since one cannot know in advance what b value the real data features and thus choose parameters accordingly, we maintain that the approach presented by Tormann et al. [2014] <implemented in this FEX code> cannot be used on real data sets as its results depend on the assumed input b values chosen to derive its parameters. [...] We encourage the reader to download the codes (see Acknowledgements), try different parameter sets and explore the large variety of b value maps that one can obtain from a single data set in the absence of an objective criteria. "