Seismo-Hydrogeodynamic Effects in Groundwater Pressure Changes: A Case Study of the YuZ-5 Well on the Kamchatka Peninsula

Round 1

Reviewer 1 Report

1. row numbers 38, 50, 484, "GP" may a miss typo that should be "HP"

2. the words "pressure jump" readers may think every coseismic event cause the water level going up. however, according to table 3, those are up and down. I suggest you to change the word "fluctuation"

3. figure 2, is going to show the eq event number 12 (170907 23:34), but it does not look to have dramatic changes

4. in figure 3, there are 2 curves "black" and "light red" but those are not explained clearly.

Author Response

We are sending a revised version of the manuscript. We have taken into account all comments of the reviewer. We are grateful to the reviewer because, in our opinion, the reviewer’s comments allowed us to improve the manuscript.

Following changes have been made in the paper according to the comments

1. row numbers 38, 50, 484, "GP" may a miss typo that should be "HP"

Corrected

2. the words "pressure jump" readers may think every coseismic event cause the water level going up. however, according to table 3, those are up and down. I suggest you to change the word "fluctuation"

Replaced with "fluctuation".

3. figure 2, is going to show the eq event number 12 (170907 23:34), but it does not look to have dramatic changes

Please note the date of EQ No. 12 is July 17, 2017 (Table 3), while Figure 2 shows the time interval from September 5 to September 14, 2017, which does not include EQ No. 12.

4. 4. in figure 3, there are 2 curves "black" and "light red" but those are not explained clearly.

 Figure 3 and caption edited.

Reviewer 2 Report

The paper is a concrete one. I donot have much comment on this pape except the following:

1) English may be slightly edited;

2) Methodology part should be more elaborated;

For Editor:

1) I did not check the plagiarism & self citation, so please take care by you. 

Author Response

We are sending a revised version of the manuscript. We have taken into account all comments of the reviewer. We are grateful to the reviewer because, in our opinion, the reviewer’s comments allowed us to improve the manuscript.

Following changes have been made in the paper according to the comments

1) English may be slightly edited;

The text and captions have been edited. Corrections are highlighted in yellow.

2) Methodology part should be more elaborated;

We believe that the edited version of the text strengthened the methodological content of the work.

Reviewer 3 Report

The paper is well written and has a acceptable quality of analysis. In this study field data has been used. What do the authours think about satellite data such as Grace in determining the level of under ground water? Up to know different mechanisms have been proposed in the field of occurence of earthquake precursors. Is it possible definetly to consider change in level of ground water as a potential earthquake precursor. If yes, based of what mechanism can it be justified? Is the mechanism of underground water different in coastal regions and far from coast? 

Author Response

1. What do the authors think about satellite data such as Grace in determining the level of underground water?

Satellite data, in particular the Grace mission, is widely are used in the study of large-scale hydrogeological processes. These data are used to diagnose coseismic displacements of the Earth's surface during strong earthquakes.

In the present work, we use the traditional method of precision borehole observations to investigate the effects of seismicity on changes in groundwater pressure.

2. Up to know different mechanisms have been proposed in the field of occurrence of earthquake precursors. Is it possible definitely to consider change in level of ground water as a potential earthquake precursor. If yes, based of what mechanism can it be justified?

In this paper, we consistently pursue the idea of a quasi-elastic mechanism of the observed barometric and tidal effects in changes in the level/pressure of groundwater, as well as two cases of the manifestation of supposed hydrogeodynamic precursors. This applies only to the well in question, and possibly also to similar wells.

An alternative mechanism for formation of hydrogeodynamic and hydrogeochemical precursors is the development of dilatancy and microfracturing in water-bearing rocks, as well as a change in hydraulic connections between various fragments of the aquifer system associated with observation well.

 In the considered well, we did not find any evidence of the manifestation of dilatancy mechanism, while in other observation wells there were changes in chemical composition of water. In well E-1, a uniform manifestation of a precursor in pressure decrease is observed. This may indicate the development of dilatancy and an increase in capacity of water-bearing rocks.

3. Is the mechanism of underground water different in coastal regions and far from coast?

Of course, there are features of groundwater formation in coastal areas and far from sea coasts. This is a special issue.

If we consider the YuZ-5 well as located near the sea coast, then we have, perhaps, small shifts in the phase shift of individual tidal waves due to their distortion by similar waves of the ocean tide. However, the effect of ocean tide on the tidal pressure response of groundwater is small. This issue was considered earlier in our works, presented in the List of References.