CO₂ Dynamics in a Mofette: Measurement and Modeling

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

see my comments in the attached PDF

Comments for author File: Comments.pdf

Author Response

Thank you for the valuable comments and constructive suggestions to improve our manuscript. We are grateful for the detailed review and the recommendations for enhancing the analysis and presentation of our results.

General Comments

We appreciate the specific recommendations for additional analyses. Regarding the daily variations and their potential relationship to sunrise as described by Kies et al. (2015), we prepared two figures showing concentration time series covering six randomly selected sunrises marked with black vertical lines. These figures do not reveal the sunrise-related effects reported by Kies et al., suggesting that the diurnal patterns in our mofette may be primarily driven by temperature and atmospheric pressure variations rather than solar radiation effects. We therefore did not include this analysis in the main manuscript, as no clear correlation can be observed.

To better justify the potential geological origin of the observed burst events, we have included additional text in lines #327-#332 of the revised manuscript: "These sudden bursts could result from atmospheric effects; however, the violent nature of the increases in the CO₂ concentration may indicate involvement of geological processes. Similar behavior has been observed at CO₂-rich mineral springs in the Covasna area, where random gas bursts occur through water at minutes to tens of minutes intervals, suggesting modulation by underground gas-flux variations." We emphasize that this represents only one possible explanation for the observed phenomena. Due to insufficient evidence to conclusively determine the underlying mechanisms, we present this as a possible explanation. (That would require further investigation with additional geological and geophysical methods to validate.)

Regarding the Reviewer's suggestion to examine potential correlations between CO₂ spikes and seismic activity, we prepared an additional figure overlaying our concentration time series with earthquake data from the Vrancea seismic zone. This figure displays CO₂ concentrations on the left y-axis and earthquake magnitudes on the right y-axis, with black vertical lines indicating individual earthquake events (M ≥ 3.5). Visual inspection of this overlay reveals no apparent correlation between seismic events and changes in CO₂ concentration. Given the relatively low number of significant earthquakes during our monitoring period, statistical analysis was not feasible. Unfortunately, we were unable to find reliable rainfall data for our study site during the measurement period, preventing us from conducting the rainfall correlation analysis suggested by the Reviewer.

Technical Comments

Comment 0: I propose that you enlarge Figs. 7, 8, 9, 10, and 12 (use the full width of the page). The legend of the right panel of Fig.10 hides the best part of the data. Maybe you can just remove it.

Response 0: The figures will be displayed at full page width in the final published version. The current layout limitation is due to the submission template format. The legend positioning will be adjusted as suggested by the Reviewer.

Comment 1: #2 remote sensing is misleading, maybe better multi-sensor

Response 1: Text modified as suggested by the Reviewer: "Using a custom-built remote multi-sensor device, we monitored the gas concentrations..."

Comment 2: #195 explain alpha

Response 2: Text modified as suggested. We added an explanation of the α parameter in line #216: "with parameters r₀, T₀, and scaling exponent α. These parameters control the temperature dependence, with α determining the steepness of the response."

Comment 3: #256, you fitted slopes to three distinct frequency regimes in Fig. 8. These findings have to be discussed.

Response 3: We added discussion as suggested by the Reviewer in lines #277-280: "Moreover, we can observe three distinct frequency regimes where the PSD scales according to a power-law function with frequency. While the underlying mechanisms for this scaling remain unclear, this behavior seems notable. For each of these regimes, we fitted a power function, shown in Figure 8b."

Comment 4: #264 Here, the following text of the figure caption of Fig.10 should appear: "After the initial bursts, multiple subsequent bursts appear, which is especially noticeable in the right figure. One can also see that as a result of the sudden gas upflow, mixing occurs between different layers. As a result of the mixing, the usually present concentration gradient (as a function of height) is less pronounced."

Response 4: Text added as suggested in lines #288-290: "Following the initial bursts, multiple subsequent bursts appear, which is especially noticeable in the right panel. The sudden gas up-flow causes mixing between different layers, making the usual concentration gradient less pronounced."

Comment 5: #279 Give average values of CO₂ flux in mol/s as well as in m³/h. Maybe it is worthwhile to present a table with descriptive statistics (min, max, mean, median, skewness,…) for CO₂ concentrations at each depth level, CO₂ flux, temperature, and pressure.

Response 5: We have modified the units in Figures 11 and 12 to consistently use m³/h throughout the manuscript, eliminating the need for unit conversion tables as suggested by the Reviewer.

Comment 6: #303 This information (#303..308) is new and thus should be moved to the "Results and Discussion".

Response 6: Text included in Results and Discussion in lines #285-287: "Besides the typical behavior, we observed multiple events where a sudden burst of anomalous outflow occurred within a few minutes. In some of these events, the CO₂ concentration at the uppermost sensor exceeded 60%." and lines #288-290: "Following the initial bursts, multiple subsequent bursts appear, which are especially noticeable in the right panel. The sudden gas up-flow causes mixing between different layers, making the usual concentration gradient less pronounced."

Thank you very much for the observation you have sent to us.

Reviewer 2 Report

Comments and Suggestions for Authors

This article aims to address the dynamics of carbon dioxide (CO₂) emissions from natural sources—a critical issue in climate science and environmental research. The methodology is sound, and the content is comprehensive and well-developed. Specific revision suggestions are as follows: 

1. The calibration process of the sensors (e.g., zero-point drift correction) is not sufficiently detailed. Could high humidity (near the dew point) and CO₂ concentration fluctuations (0–95%) cause sensor response delays or drift?
2. The assumption of "periodic boundary conditions" in the model may lack realism. Geological structures are often more complex (e.g., anisotropic permeability dominated by fracture zones). The limitations of this simplification should be discussed.
3. In Figure 8b, the significance of the 12/24-hour periodic peaks in the power spectral density (PSD) analysis should be quantified (e.g., via F-tests). Was instrumental noise ruled out as a potential confounding factor?
4. The analysis of sudden CO₂ emission events (e.g., sharp spikes) is insufficient. While geological processes are hypothesized as a potential cause, regional seismic activity data or fluid pressure variation records were not integrated to support this inference.
5. The model exhibits notable deviations in predicting peak events (e.g., the right panel of Figure 10). The reasons for these discrepancies should be explored (e.g., was rapid recharge of geological fluids not accounted for in the model?).
6. The potential impacts of CO₂ emissions on local ecosystems or climate (e.g., soil acidification or greenhouse effects) are not discussed. These aspects should be addressed to contextualize the broader implications of the findings.

Author Response

Thank you for the valuable comments and constructive suggestions to improve our manuscript. We are grateful for the detailed review and the recommendations for enhancing the analysis and presentation of our results.

Technical Comments

Comment 1: The calibration process of the sensors (e.g., zero-point drift correction) is not sufficiently detailed. Could high humidity (near the dew point) and CO₂ concentration fluctuations (0–95%) cause sensor response delays or drift?

Response 1: Text modified in lines #169-170: "Its integrated humidity compensation (using DHT11 sensor data for humidity compensation) and temperature stability (temperature coefficient: 0.025 vol%/°C) ensure consistent performance in the conditions typical of mofettes [18]." We utilized the sensor's integrated humidity compensation capabilities, with zero-point calibration performed in ambient air outside the mofette. We relied on the manufacturer's specified characteristics rather than conducting gas mixture calibration (air-CO₂, nitrogen-CO₂).

Before this study, we conducted pilot measurements during the winter months (October 2021 - February 2022), as included in lines #82-86. During these tests, we observed moisture condensation on sensors due to low external temperatures, leading to PCB (Printed Circuit Board) corrosion (image below) and anomalous readings.

To prevent these issues, we selected a measurement interval where moisture condensation did not occur and manufactured new corrosion-resistant PCBs (Image below).

As noted in line #171, this sensor (STC31) was chosen for its proven reliability in wet mofette conditions (https://link.springer.com/article/10.1007/s10661-023-12114-8) where humidity levels are consistently near the dew point. No additional humidity testing was performed on the sensors, and during our summer measurement interval, we did not observe the extreme anomalous values that were encountered during the initial pilot study.

Comment 2: The assumption of "periodic boundary conditions" in the model may lack realism. Geological structures are often more complex (e.g., anisotropic permeability dominated by fracture zones). The limitations of this simplification should be discussed.

Response 2: As suggested, we highlighted the simplifications and limitations of our model. Text modified in lines #206-209: "In our model, CO₂ flows through a system of chambers, corresponding to a highly simplified representation of natural cavities arranged in a square grid. Indeed, this approach oversimplifies the complex, heterogeneous fracture networks with anisotropic permeability and variable gas supply characteristic of real geological systems." As a physical model, we necessarily make simplifications to create a tractable numerical framework, and we now briefly discuss the limitations of the current model assumptions.

Comment 3: In Figure 8b, the significance of the 12/24-hour periodic peaks in the power spectral density (PSD) analysis should be quantified (e.g., via F-tests). Was instrumental noise ruled out as a potential confounding factor?

Response 3: The observed 12/24-hour peaks correspond to well-established atmospheric diurnal cycles that are physically expected in this system, making formal statistical significance testing redundant. Instrumental noise was not specifically investigated as a confounding factor. However, the coherent response across the entire sensor array demonstrates that these patterns reflect genuine physical processes rather than measurement artifacts.

Comment 4: The analysis of sudden CO₂ emission events (e.g., sharp spikes) is insufficient. While geological processes are hypothesized as a potential cause, regional seismic activity data or fluid pressure variation records were not integrated to support this inference.

Response 4: As this comprehensive geological analysis is not the scope of the current article, we focused on the gas dynamics at the measurement site. We have added a discussion in lines #332-337: "These sudden bursts could result from atmospheric effects; however, the violent nature of the increases in the CO₂ concentration may indicate involvement of geological processes. Similar behavior has been observed at CO₂-rich mineral springs in the Covasna area, where random gas bursts occur through water at minutes to tens of minutes intervals, suggesting modulation by underground gas-flux variations." Additionally, in lines #349-357, we note that: "Occasional meteoric events such as heavy rain episodes able to produce sudden spikes in the gas-flux time series, as Woith et al. reported at Hartoušov, Czech Republic [10] can be excluded since no such events occurred during our monitored time interval. Other parameters, likely of geological origin, could play a role in the gas outflow and its long-term (months), as pointed out elsewhere in the broader area by Airinei [15], and short-term (minutes, hours; this study) modulations. The actual geological, regional, and/or local causes of the observed atmosphere- and weather independent variations have to be investigated in the future using a much wider spectrum of interdisciplinary tools than those used in this study, restricted to one single spot on Earth's surface."

 

Comment 5: The model exhibits notable deviations in predicting peak events (e.g., the right panel of Figure 10). The reasons for these discrepancies should be explored (e.g., was rapid recharge of geological fluids not accounted for in the model?).

Response 5: Our model cannot account for rapid geological fluid recharge processes, as we do not have data on subsurface geological parameters or fluid pressure variations. The geological explanations are presented as possibilities rather than affirmations due to this data limitation. As stated in lines #332-334: "the violent nature of the increases of the CO₂ concentration may indicate involvement of geological processes" and in lines #351-356: "Other parameters, likely of geological origin, could play a role in the gas outflow and its long-term (months), as pointed out elsewhere in the broader area by Airinei [15], and short- term (minutes, hours; this study) modulations. The actual geological, regional, and/or local causes of the observed atmosphere- and weather independent variations have to be investigated in the future using a much wider spectrum of interdisciplinary tools than those used in this study, restricted to one single spot on Earth’s surface." Our current model focuses on atmospheric pressure and temperature effects.

Comment 6: The potential impacts of CO₂ emissions on local ecosystems or climate (e.g., soil acidification or greenhouse effects) are not discussed. These aspects should be addressed to contextualize the broader implications of the findings.

Response 6: The reviewer's claim is valid and important. However, our research and its time series results consider the local dynamics of the focused CO₂ emanation in a mofette, which is just a single spot on Earth's surface. Soil acidification could be, at most, a local effect due to such focused emanation we investigated on the mofette whose wooden pit bottom is in a clay bed below the soil level. That does not exclude, of course, lateral soil level diffusion of the gas to a local extent. Diffuse  CO₂ emanations, occurring extensively in the broader area, could have, indeed, a significant soil acidification effect, but this aspect is beyond the scope of this article. Actually, diffuse soil gas emanation mapping and studies are underway in the area (Covasna town), and they will address the acidification problem too. Similarly, those investigations related to areal diffuse emanation fluxes and time-dependent variations, along with the results of previous studies, will allow to evaluate the contribution of geogenic CO₂ to the atmospheric greenhouse effects and to contextualize all relevant findings obtained in the whole area. Therefore, no new text was added.

We thank the Reviewer for the thorough and constructive feedback.

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript presents an original study on the dynamics of CO₂ emissions from a mofette located in Covasna, Romania. The authors used a customized, low-cost, high-temporal-resolution remote sensing system to continuously monitor CO₂ concentration, pressure, and temperature for over seven months. A convection-diffusion model and a new numerical simulation based on a chamber are used to estimate and predict CO₂ fluxes. The topic is relevant and timely, particularly in the context of growing interest in CO₂ emission monitoring and underground gas transport processes.
The manuscript is generally well structured, based on a solid methodological foundation, and contains innovative experimental and modeling elements. However, it requires substantial revisions to improve scientific clarity, accuracy, and integration of the geophysical context.

INTRODUCTION

Lines 34-36: The authors assert that focused CO₂ emissions like those in mofettes have received less attention than diffuse emissions. However, this is not sufficiently supported by recent literature. I recommend the author to cite additional reviews or studies that compare diffuse and focused degassing globally

Lines 10-14: Although the therapeutic and geological importance is highlighted, the environmental importance of natural CO₂ degassing is underestimated. I suggest expanding the introductory discussion to include implications for climate models and risk assessment in CO₂-rich environments.

Location and Geological Background

Lines 91-97: The discussion of crustal and mantle sources is relevant, but the geological implications for the observed temporal patterns are not explored. You can link these geological features to the potential causes of the short-term peaks observed in your results.

METHODOLOGY

Lines 122-124 : L'approximation en régime permanent (∂C/∂t = 0) est en contradiction avec la documentation ultérieure sur les fluctuations dynamiques. Pouvez vous justifiez pourquoi un modèle en régime permanent est approprié malgré des caractéristiques transitoires évidentes?

Lines 153-157: The sensors are located 20 cm from the wall; the authors claim that the proximity to the wall does not influence the results. Please include references or simulations validating that the effects of proximity to the wall are negligible in the gas mixture for the measured flow rates.

MODELING THE GAZ FLOW

Lines 1866200: The 10×10 chamber grid assumes homogeneity and constant flow between chambers. Please add a brief discussion here on the limitations of this assumption, particularly given the potential heterogeneities in fracture permeability and gas supply.

RESULTS

Lines 262 to 264: The study notes “erratic anomalies” and peaks in CO₂ emissions, but does not analyze or model them separately. Here, it is recommended to use spectral, wave, or statistical methods of peak detection to characterize these events. Discuss their implications in more detail.

Lines 283-285 and Figure 12: Although the model visually follows the observed trends, no quantitative fit measures are provided. Please include R², RMSE, or BIC for each of the nine fitted intervals to rigorously evaluate the model's performance.

CONCLUSION

The authors hypothesize that geological processes could explain the anomalies, but without providing further details. Discuss potential triggers (e.g., crustal stress, gas slugging, pressure instabilities) and indicate whether seismic or geophysical monitoring exists or is planned, to further support your conclusion.

VISUALS AND FIGURES

-Figure 1 : Add coordinates to the maps

-Figure 10 :  Explanations should be included in the text and not in the figure title. You can use a single legend for both figures to avoid covering the variations in the curves.

 

REFERENCES

16 references is a very low number for a scientific article!!! If we exclude data sources and initial references,

I strongly recommend adding more references to the text, especially since many sentences need to be referenced.

Author Response

Thank you for the valuable comments and constructive suggestions to improve our manuscript. We are grateful for the detailed review and the recommendations for enhancing the analysis and presentation of our results.

Technical Comments

Comment 1: Lines 34-36: The authors assert that focused CO₂ emissions like those in mofettes have received less attention than diffuse emissions. However, this is not sufficiently supported by recent literature. I recommend that the author cite additional reviews or studies that compare diffuse and focused degassing globally.

Response 1: We thank the Reviewer for this valuable observation. Text modified and additional references added as shown in lines #40-50: "Woith et al. emphasize that 'Despite the obvious potential, systematic studies of mofettes to monitor magmatic processes at depth are rare'. Most studies address geogenic CO₂ flux estimates and their contribution to the atmospheric CO₂ levels in active volcanic areas where both diffuse and focused gas emanations are intense and readily measurable. However, 'non-volcanic CO₂ fluxes in «colder» environments are much greater than generally assumed' as Mörner and Etiope observed. Their links to seismotectonic structures are discussed by Barnes et al. On the other part, geothermal systems, related or unrelated to volcanism, are geogenic sources of CO₂ emission in both diffuse and focused manner. In the Sousaki geothermal field in Greece, for example, 'point sources in the same area' contribute for less than 1/10 of the total output."

Comment 2: Lines 10-14: Although the therapeutic and geological importance is highlighted, the environmental importance of natural CO₂ degassing is underestimated. I suggest expanding the introductory discussion to include implications for climate models and risk assessment in CO₂-rich environments.

Response 2: Text modified as suggested in lines #23 and #28-32: "They are commonly found in volcanic and seismotectonically active areas, providing a natural laboratory for studying concentrated CO₂ emissions." and "On the other side, risk assessment in CO₂ gas-rich environments is another focus in mofette studies. Too, along with diffuse regional CO₂ emissions, locally focused natural degassing in mofettes contributes to the global carbon cycle; hence their environmental importance cannot be neglected or underestimated when discussing climate models."

Comment 3: Lines 91-97: The discussion of crustal and mantle sources is relevant, but the geological implications for the observed temporal patterns are not explored. You can link these geological features to the potential causes of the short-term peaks observed in your results.

Response 3: Yes, that is right. Addressing the "geological implications" was beyond the scope of this research, which was rather focused on the dynamics of focused gas emanation in a mofette, a single spot on Earth's surface. Even though we obtained a 7-month-long time series in that single spot, the information gathered, in our opinion, is far not enough to discuss the much broader subject of "geological implications", i.e, space- and time-related geological effects of the monitored emanations. However, the "potential causes of the short-term peaks observed" can indeed be discussed to a limited extent. We added just a short discussion on this aspect in the modified Conclusions chapter, as another Reviewer claimed too.

Comment 4: Lines 122-124: The steady-state approximation (∂C/∂t = 0) contradicts the subsequent documentation on dynamic fluctuations. Can you justify why a steady-state model is appropriate despite evident transient characteristics?

Response 4: The steady-state approximation is a necessary assumption for obtaining an analytical solution to the concentration distribution problem. As stated in lines #141-143: "...we assumed that the outflow yield is quasi-stationary (the change in the gas flow yield is slower than the time needed to achieve the equilibrium state)." This assumption is consistent with our observations that the analytical exponential concentration function approximates well the experimentally measured concentration curves in the majority of time windows. The short-term fluctuations on seconds-to-minutes timescales represent a different physical process - rapid back-and-forth gas movement between underground and surface chambers, evidenced by the strong correlation between sensors (lines #294-296): "...the time series measured by the individual sensors are strongly correlated (the concentrations measured by the sensors increase and decrease in sync)." To address these rapid fluctuations while maintaining the steady-state framework for yield calculation, we employed two-minute averaging (lines #300-301): "...we performed a two-minute averaging on the time series measured by the sensors."

Comment 5: Lines 153-157: The sensors are located 20 cm from the wall; the authors claim that the proximity to the wall does not influence the results. Please include references or simulations validating that the effects of proximity to the wall are negligible in the gas mixture for the measured flow rates.

Response 5: A comprehensive computational fluid dynamics simulation study to validate wall effects would constitute a separate research effort beyond the scope of this experimental study. Our justification is based on the physical characteristics of the system as stated in lines #175-177: "Given that the observed flow velocities are on the order of centimeters per second, the proximity to the walls does not significantly impact the gas distribution compared to the center of the chamber, nor does it affect the laminarity of the flow." The low Reynolds number flow regime (given the slow velocities and high CO₂ density) suggests minimal boundary layer effects at 20 cm distance from walls in a chamber with dimensions 165 cm × 153 cm. Additionally, the strong correlation observed between sensors at different heights (eg, Figure 9) supports the assumption that the measurement location captures representative gas dynamics rather than localized wall effects.

Comment 6: Lines 186-200: The 10×10 chamber grid assumes homogeneity and constant flow between chambers. Please add a brief discussion here on the limitations of this assumption, particularly given the potential heterogeneities in fracture permeability and gas supply.

Response 6: As suggested, we highlighted the simplifications and limitations of our model. Text modified in lines #206-209: "In our model, CO₂ flows through a system of chambers, corresponding to a highly simplified representation of natural cavities arranged in a square grid. Indeed, this approach oversimplifies the complex, heterogeneous fracture networks with anisotropic permeability and variable gas supply characteristic of real geological systems." As a physical model, we necessarily make simplifications to create a tractable numerical framework. The 10×10 chamber grid with homogeneous properties and constant inter-chamber flow represents an idealized system that cannot capture the spatial variability in fracture permeability and heterogeneous gas supply characteristic of real geological systems, and we now briefly discuss these limitations of our current model assumptions.

Comment 7: Lines 262 to 264: The study notes "erratic anomalies" and peaks in CO₂ emissions, but does not analyze or model them separately. Here, it is recommended to use spectral, wave, or statistical methods of peak detection to characterize these events. Discuss their implications in more detail.

Response 7: While detailed spectral analysis and statistical peak detection methods would provide valuable insights, such comprehensive characterization of anomalous events falls beyond the scope of this study, which focuses primarily on the general gas dynamics and atmospheric correlations. The observed peak events represent a relatively small fraction of our dataset and occur sporadically, making systematic statistical analysis challenging. Our current analysis provides qualitative identification and basic temporal characterization of these events (lines #282-286), establishing their existence and general behavior patterns. Comprehensive quantitative analysis of these anomalous events would constitute a separate research focus requiring specialized signal processing methodologies and would benefit from longer monitoring periods to accumulate sufficient event statistics for robust analysis. 

Comment 8: Lines 283-285 and Figure 12: Although the model visually follows the observed trends, no quantitative fit measures are provided. Please include R², RMSE, or BIC for each of the nine fitted intervals to rigorously evaluate the model's performance.

Response 8: We acknowledge that quantitative fit measures would strengthen the model evaluation. However, calculating detailed statistical metrics such as R², RMSE, or BIC for each of the nine fitted intervals was not implemented in the current analysis due to time constraints. We appreciate this suggestion and will consider incorporating these quantitative measures in future studies to provide more rigorous model performance assessment.

Comment 9: The authors hypothesize that geological processes could explain the anomalies, but without providing further details. Discuss potential triggers (e.g., crustal stress, gas slugging, pressure instabilities) and indicate whether seismic or geophysical monitoring exists or is planned, to further support your conclusion.

Response 9: Detailed analysis of specific geological triggers such as crustal stress, gas slugging, or pressure instabilities requires geophysical data that was not collected as part of this study. We emphasize that we do not state geological processes as the definitive cause of observed anomalies; rather, we suggested this as a possibility, as stated in lines #332-334: "...the violent nature of the increases of the CO₂ concentration may indicate involvement of geological processes." and in lines #351-356: "Other parameters, likely of geological origin, could play a role in the gas outflow and its long-term (months), as pointed out elsewhere in the broader area by Airinei, and short- term (minutes, hours; this study) modulations. The actual geological, regional, and/or local causes of the observed atmosphere- and weather independent variations have to be investigated in the future using a much wider spectrum of interdisciplinary tools than those used in this study, restricted to one single spot on Earth’s surface." No geological measurements were performed at the study site, nor is seismic or geophysical monitoring currently planned. For completeness, we plotted earthquake data from the Vrancea seismic zone (M≥3.5) alongside our CO₂ concentration time series (figure below), visual inspection revealed no apparent correlation between earthquake occurrences and CO₂ concentration changes. Given the limited number of seismic events during our monitoring period, meaningful statistical analysis was not feasible.

 

Comment 10: Figure 1: Add coordinates to the maps
Response 10: Coordinates added to Figure 1 as suggested. The mofette location (45°51'10.7"N, 26°11'19.5"E) is marked on the map.

Comment 11: Figure 10: Explanations should be included in the text and not in the figure title. You can use a single legend for both figures to avoid covering the variations in the curves.

Response 11: Figure 10 modified as suggested by the Reviewer. A single legend is now used for both panels to avoid covering the data variations in the curves.

Comment 12: 16 references is a very low number for a scientific article!!! If we exclude data sources and initial references, I strongly recommend adding more references to the text, especially since many sentences need to be referenced.

Response 12: We have added additional references to the manuscript as suggested by the Reviewer. The newly included references are: Response 12: We have added additional references to the manuscript as suggested by the Reviewer: Roberts et al. (2011), Woith et al. (2022), Werner et al. (2019), Mörner and Etiope (2002), Barnes et al. (1978), and D'Alessandro et al. (2006).

We thank the Reviewer for the thorough and constructive feedback.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Dear authors,

thanks for adressing my concerns/comments properly and congratulations to this nice piece of work. The info about sunrise and earthquakes is interesting, but remains among us - a pity. For future research: you should not only look for large magnitude earthquakes, instead you should calculate the "strain impact" of ALL events (small, nearby may have similar effects as large and distant earthquakes) at your monitoring site, e.g. by calculating the seismic energy density as proposed by Wang & Mange (2010?). 

Best regards, Heiko Woith

Reviewer 3 Report

Comments and Suggestions for Authors

Dear author, 
Thank you for your detailed and thoughtful responses to the comments. I have carefully reviewed your responses point by point and the corresponding revisions to the manuscript.
I note that you have addressed almost all of the concerns in a constructive and rigorous manner. Your modifications and responses were well-argued and justified. It is important to note that the revised manuscript is now more complete and, in my opinion, academically acceptable.
I am satisfied that my comments have been effectively addressed and now believe that the revised manuscript meets the journal's standards.
For all these reasons, I support the publication of this manuscript in Geosciences after the careful revisions.

Sincerely,