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

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 (Mw 7.1) and

the 2020Mw 6.4 Puerto Rico earthquakes.We show in this comment

that the method applied by Kelian Dascher-Cousineau

et al. (2020) deviates in at least six substantial and not well-documented

aspects from the original FTLS method. As a consequence,

they used for example in the Ridgecrest case only 1%

of the data available to estimate b-values and from a small subvolume

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.