The study performs statistical analysis of laboratory fracture experiment data to formulate a precursor based on the coefficient of variation of selected seismicity attributes. The methodology is then applied to the seismicity of the Parkfield segment of San Andreas Fault in California. The authors conclude that the results confirm "the existence of precursor characteristics before rock fracture" and "the credibility of the CV describing the precursors".

The general topic of the study -- testing selected labquake precursory phenomena in observed seismicity -- is interesting and appropriate for NPG. However, the science content and technical level of the work are below the standards of NPG. The work needs substantial restructuring and revising before it can be re-evaluated for possible publication.

I notice that the authors decided to either ignore or only cosmetically address the comments of the two reviewers -- this is unfortunate, since readers most probably will have similar concerns. I strongly suggest the authors to reconsider the reviewers' comments.

In addition, I notice the following issues:

1) The method description is unacceptable. It is very informal and sketchy, not allowing one to reproduce the results. This applies to the digital speckle correlation method, estimating displacement and strain from experiment observations, and defining the precursor in observations. The work in its current form cannot be evaluated, since the main examined quantities remain undefined.

2) Please define the examined precursor (Is it increase of CV, decrease of the average distance to the crack, or something else?). A formal reproducible definition should be given. Next, I fail to see what is claimed to be a precursor in Fig. 8a. I see neither a systematic increase or decrease of the distance as a failure approach. With this variability and inconsistency of results in five lab samples, it is hard to expect that the precursor will work in observations. I also fail to see how Fig. 8b supports authors' conclusions. What do we see here -- an increase at 70% or decrease at 100%? What about stability of this result?

3) Figures 3,4,5,6 have unnecessarily many panels with largely repeating information. Think of moving most of the panels to SI, and only keeping the most informative figures in the main text. The captions are repetitive -- please rewrite.

4) The text is clumsy, repetitive, and unnecessarily long. I suggest revising the presentation in order to formally show (with all relevant equations) and justify the main steps of the analysis. It is also advisable to improve the grammar and style.