Herewith I have enclosed my comments on paper titled "Analysis of seismic strain releases related to tidal stress before the 2008 Wenchuan earthquake". Overall the authors have made observation that there is a seismic strain release, but the authors have to explain further why such behaviourial changes oberved between PEQs and NEQs.
We thank Venkatanathan for the comments. Some researches reported the tidal triggering of earthquakes prior to moderate to large earthquakes (Tanaka et al., 2002b; Tanaka, 2010, 2012; Li et al., 2018). They investigated the tidal triggering of earthquakes in terms of event count. We investigated the tidal triggering of earthquakes before the Wenchuan earthquake in terms of seismic strain release,but not event count. Therefore the behaviourial changes oberved between PEQs and NEQs result from the tidal triggering of earthquakes prior to the Wenchuan earthquake indeed. The tidal triggering of earthquakes focus on the promoting effect of the tidal stresses, but our results reveal not only the promoting effect, but also the inhibiting effect of the tidal stresses. The increasing tidal stress will promote the occurrence of earthquakes, while the decreasing tidal stress will inhibit the occurrence of earthquakes when a large earthquake is impending.
CC3: 'Reply on CC2', Natarajan Venkatanathan, 07 Feb 2022
Dear authors, I agree you have worked on seismic strain release. You have observed behaviourial changes of PEQs and NEQs , but there is no explanation that why NEQs decreases prior to the main event compared to the PEQs. You need to explain, when NEQs decreases due to decreasing tidal stress, then why PEQs increases.
CC4: 'Reply on CC2', Natarajan Venkatanathan, 07 Feb 2022
Dear authors, I agree you have worked on seismic strain release. You have observed behaviourial changes of PEQs and NEQs , but there is no explanation that why NEQs decreases prior to the main event compared to the PEQs. You need to explain, when NEQs decreases due to decreasing tidal stress, then why PEQs increases.
The Earth tide produces cyclic stress variations in the Earth. These stress variations, of the order of 1000~10000 Pa, are far smaller than the tectonic stress. When the stress in the focal region is at lower values, the tidal stress can not influence the occurrence of earthquakes, but when it is close to a critical condition to release a large rupture, the tidal stress could take effect on the occurrence of earthquakes. The tidal stress increase will promote the occurrence of earthquakes, making the seismic strain release accelerate for PEQs (corresponding to the increase of k in Fig.4c), and when the tidal stress decrease will inhibit the occurrence of earthquakes, making the seismic strain release decelerate for NEQs (corresponding to the decrease of k in Fig.4c).
Herewith I have enclosed my comments on paper titled "Analysis of seismic strain releases related to tidal stress before the 2008 Wenchuan earthquake".
Analysis of seismic strain releases related to tidal stress before the 2008 Wenchuan earthquake
Xuezhong Chen et al.
The analysis shows results for PEQ (positive earthquakes) defined as when (delta)TCFS >0. Did you also do the analysis on PEQ defined as TCFS>0? If so, what were the results? Can you discuss how the choice of PEQ impacts your interpretation and the underlying physics? I think the observation is pretty robust, but there is a lot more analysis you could provide regarding your interpretation of the underlying physics and earthquake processes. As it stands, it is simply an interesting observation.
Can you resolve any changes in behavior with shorter time resolution? You average over 5-years. Is there any change in behavior that you can resolve within the period of time when Rk is increasing?
Why should k(neg) decrease when approaching the Wenchuan earthquake? It seems more intuitive that both k(pos) and k(neg) should increase, even if k(pos) increases faster.
There is another change in behavior around 1999, which can be seen in Figure 4a and 4c. Is there any explanation for that? Is it related to the change in instrumentation?
Figure 1b, what component of strain are you showing?
You write, “as the length of time with (delta)TCFS>0 is almost the same as that with (delta)TCFS<0”. What do you mean by almost? Do you account for the difference in your analysis? You should compare observed versus actual expected, not observed versus “almost” expected. This could impact your results.
There are some minor language problems, that could be fixed by having the manuscript reviewed by a more experienced English writer.