Comment on "Two Foreshock Sequences Post Gulia and Wiemer (2019)" by Kelian Dascher-Cousineau, Thorne Lay, and Emily E. Brodsky Comments and Replies

Dascher-Cousineau et al. (2020) apply the so-called foreshock traffic-light system (FTLS) model proposed by Gulia and Wiemer (2019) to two earthquake sequences that occurred after the submission of the model: the 2019 Ridgecrest (M,,, 7.1) and the 2020 M,,, 6.4 Puerto Rico earthquakes. We show in this com-ment that the method applied by Kelian Dascher-Cousineau et al. (2020) deviates in at least six substantial and not well-doc-umented aspects from the original FTLS method. As a conse-quence, they used for example in the Ridgecrest case only 1% of the data available to estimate b-values and from a small sub-volume of the relevant mainshock fault. In the Puerto Rico case, we document here substantial issues with the homogeneity of the magnitude scale that in our assessment make a meaningful analysis of b-values impossible. We conclude that the evaluation by Dascher-Cousineau et al. (2020) is misrepresentative and a not a fair test of the FTLS hypothesis.