the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Supervision of seismic velocity models of the Reykjanes Peninsula Rift, SW Iceland
Abstract. Most methods for processing seismological data require a suitable velocity model characteristic for the given region being defined. This is also the case of the Reykjanes Peninsula (RP) in SW Iceland, where the REYKJANET seismic network was built to monitor local seismicity in the rift zone. At present, four previously published 1D velocity models (SIL, BRA, TRY and VOG) can potentially be used, prompting us to determine which one is the best. In order to address this issue, we arranged a contest in which all four 1D models and one additional 3D model (T3D) were entered. Uniform methodology for classifying the models was applied and included an analysis of: (i) post-localization travel-time residuals, (ii) residuals of the P-wave first-motion incidence angle and (iii) model-predicted and measured Rayleigh-wave dispersion. We discovered that no single model was unequivocally the most optimal, as the differences between them proved rather minor. A common shortcoming of all the models is the bias of the P-wave first motion incidence angle residuals, which may be a general problem for methods working with P-wave amplitudes (e.g., moment tensor solutions). The VOG model was selected with a weak preference.
Finally, we propose a simple method for modifying any of the 1D models by adding a station-dependent surface layer with a vertical velocity gradient. This way, a pseudo-3D model is generated which is fully competitive with a true 3D model while retaining the simplicity of 1D ray tracing. The efficiency of this correction was demonstrated using the VOG model. The corrected VOG model provides post-localization residuals comparable with the true 3D model T3D, has zero bias in predicting the P-wave first-motion incidence angles, and agrees acceptably in predicting the Rayleigh-wave phase-velocity known from other sources. While calculations with a 3D model can be clumsy, the proposed pseudo-3D model is defined by few parameters and is very easy to use. Its applicability is limited to earthquake sources deeper than the deepest lower limit of the topmost layer below the stations.
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CC1: 'Comment on egusphere-2023-2465', Růžek Martin, 30 Dec 2023
The article presents an interesting topic - comparison of different models of seismic waves propagation. The comparison of models is a challenging task because usually different metrics can be used, and it is not clear which one is the most important.
One of the important criterions of the models is their universality - in other words, answer to the question how the model works with the data that were not used during the training or the construction of the model. It would be interesting to know if the proposed model is specific to Reykjanes peninsula, or can be used for any other location.Citation: https://doi.org/10.5194/egusphere-2023-2465-CC1 -
AC2: 'Reply on CC1', Bohuslav Ruzek, 09 Jan 2024
The proposed model is only applicable for the Reykjanet area. The geological environment is so diverse that it is necessary to use an individual velocity model for each locality. The calculation procedure is general and can be used for any seismic network whose geometry is comparable to the Reykjanet network. We calculated the model parameters using a small selected part of the data, and finally tested the effectiveness of the result on a much larger data set.Citation: https://doi.org/
10.5194/egusphere-2023-2465-AC2
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AC2: 'Reply on CC1', Bohuslav Ruzek, 09 Jan 2024
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RC1: 'Comment on egusphere-2023-2465', Anonymous Referee #1, 07 Jan 2024
Below is my evaluation of the submitted articleTitle: Supervision of seismic velocity models of the Reykjanes Peninsula Rift, SW Iceland
Author(s): Bohuslav Ruzek, Jana Doubravova, and Josef HoralekThe authors evaluation of various velocity models used in Iceland, shows that they are all suitable for earthquake locations in their study region. The authors conduct elaborate tests on individual models, without any regional, geological and tectonic constraints or comparison with available seismic refraction data from their study region. Because of that, I judge the paper not to be a substantial contribution to scientific progress within the scope of Solid Earth. The paper is in fact not publishable in its present form both with respect to the scientific approach and presentation of data. As outlined in my annotated comments on the manuscript, the description of some of the methods used is not clearly explained. The manuscript needs major revision and copyediting by a proficient English speaker.
The abstract does not provide a concise and complete summary.
Some of the supplementary material may be omitted, see attached manuscript with comments.
Abstract
The abstract should state the nature of the investigation and summarizes the important conclusions. Your abstract needs to be more specific regarding the methodology and conclusions. The abstract should be a single paragraph.
Introduction needs to be rewritten. Delete the first two sentences are superfluous statements. Instead, you need to describe the tectonic framework of Iceland in a few sentences. Discuss previous research, the importance of direct measurements of crustal velocities, i.e. by refraction data, which models are relevant to the study region and what prompted this study. The near-surface velocity is dependent on crustal age, being significantly lower in volcanically active areas than in older, more eroded (Quaternary and Tertiary) formations. The RISE refraction profile (Weir et al. 2001) is the only model based on refraction data within your study area. Other profiles, such as SIST-SIL (Bjarnason et al., 1993) are east of the Reykjanes Peninsula. You need to explain where the models listed in Appendix 1 are located and you should indicate the location of these profiles in Figure 1.
Note also that you are using 1D models. Based on RISE the there is significant 2D structure within the upper crust along the Reykjanes Peninsula. The near-surface (0-3 km) velocity along the RP is poorly constrained in the 1D model by Tryggvason et al. 2002.
Figure 1 need to be redrafted showing local geology and tectonics.
2. Velocity models
Specify HOW the five velocity models are different and why?
The models in figure 2 vary with respect to velocity gradients, i.e. thickness of the upper crust. You should investigate how these variations in velocity gradients affect seismic wave propagation/ray bending depending on hypocentral depths.
Discuss trade-off between origin-time and hypocentral depth for different models.
Note that the VOG model is seemingly not based on refraction data from the Reykjanes peninsula. You need to use models based on refraction measurements within your study region, (Weir et al., 2001)
2.2. Your raypath reasoning is unclear, you need to model raypaths based on your velocity structure to explain what you mean by i.e. “flat rays”. See also raypaths modelled by Weir et al., 2001.
4. Discuss how your results match other Vp/Vs observations, i.e. Tryggvason et al. 2002, Weir et al 2001.
You need to evaluate your priory information properly prior to going into elaborate exercises evaluating models which do not apply directly to their study region. As a result your conclusions are not significant and reliable for other studies.
4 model correction scheme
I do not see the validity of this exercise as you do not evaluate its application to your earthquake data, nor do you explain how lowering the near-surface crustal velocities will affect your hypocentral depth locations. Rayleigh wave dispersion is not seemingly relevant for the local earthquake data your are presenting.
See attached manuscript with other comments.
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AC1: 'Reply on RC1', Bohuslav Ruzek, 09 Jan 2024
Dear referee Nr.1.
thanks a lot for your review. I will read your comments more carefully and I will try to reflect your objections appropriately. However some of your points are questionable, at least from my view. E.g. including refraction measurements is not possible, since no new measurements are available to us. Weir et. al. processed only P-waves but, processing of earthquakes data needs to work simultaneously with both P- and S-wave velocity models. Including R-wave dispersion into classification of velocity models makes sense to me, it gives an independent degree of the model validity. (Measured) R-wave dispersion was adopted from an already published paper so no deeper details need to be repeated in the paper, as far as I can judge. The influence of the VOG model correction to the hypocenter localization is (briefly) discussed. Etc.
Nevertheless I believe that the topic may be insufficiently informative for a broader scientific community and publishing the paper in SE may not be beneficial for most of readers. Once again, big thanks for you for your effort.
With best wishes,
Bohuslav Ruzek
Citation: https://doi.org/10.5194/egusphere-2023-2465-AC1
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AC1: 'Reply on RC1', Bohuslav Ruzek, 09 Jan 2024
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RC2: 'Comment on egusphere-2023-2465', Simone Pilia, 08 Feb 2024
Dear authors,
Thank you for submitting your work to Solid Earth.
After carefully reviewing your manuscript and taking into account the feedback provided by Reviewer 1 (R#1), I am writing in my capacity as both a reviewer and editor.
Upon my reading of the article, I tend to be largely in agreement with the assessment from R#1 that the dataset, methods, and results presented in your manuscript do not deal with a significant advancement substantial enough to justify publication in Solid Earth.
It appears to me that your work may hold promise for a more specialised journal, although it currently falls short of meeting the standards of scientific excellence and innovation expected for publication in Solid Earth. I would encourage you to carefully consider the feedback provided and to explore opportunities for refining your research to potentially meet the criteria for publication in the future.
All the best,
Simone Pilia.
Citation: https://doi.org/10.5194/egusphere-2023-2465-RC2
Status: closed
-
CC1: 'Comment on egusphere-2023-2465', Růžek Martin, 30 Dec 2023
The article presents an interesting topic - comparison of different models of seismic waves propagation. The comparison of models is a challenging task because usually different metrics can be used, and it is not clear which one is the most important.
One of the important criterions of the models is their universality - in other words, answer to the question how the model works with the data that were not used during the training or the construction of the model. It would be interesting to know if the proposed model is specific to Reykjanes peninsula, or can be used for any other location.Citation: https://doi.org/10.5194/egusphere-2023-2465-CC1 -
AC2: 'Reply on CC1', Bohuslav Ruzek, 09 Jan 2024
The proposed model is only applicable for the Reykjanet area. The geological environment is so diverse that it is necessary to use an individual velocity model for each locality. The calculation procedure is general and can be used for any seismic network whose geometry is comparable to the Reykjanet network. We calculated the model parameters using a small selected part of the data, and finally tested the effectiveness of the result on a much larger data set.Citation: https://doi.org/
10.5194/egusphere-2023-2465-AC2
-
AC2: 'Reply on CC1', Bohuslav Ruzek, 09 Jan 2024
-
RC1: 'Comment on egusphere-2023-2465', Anonymous Referee #1, 07 Jan 2024
Below is my evaluation of the submitted articleTitle: Supervision of seismic velocity models of the Reykjanes Peninsula Rift, SW Iceland
Author(s): Bohuslav Ruzek, Jana Doubravova, and Josef HoralekThe authors evaluation of various velocity models used in Iceland, shows that they are all suitable for earthquake locations in their study region. The authors conduct elaborate tests on individual models, without any regional, geological and tectonic constraints or comparison with available seismic refraction data from their study region. Because of that, I judge the paper not to be a substantial contribution to scientific progress within the scope of Solid Earth. The paper is in fact not publishable in its present form both with respect to the scientific approach and presentation of data. As outlined in my annotated comments on the manuscript, the description of some of the methods used is not clearly explained. The manuscript needs major revision and copyediting by a proficient English speaker.
The abstract does not provide a concise and complete summary.
Some of the supplementary material may be omitted, see attached manuscript with comments.
Abstract
The abstract should state the nature of the investigation and summarizes the important conclusions. Your abstract needs to be more specific regarding the methodology and conclusions. The abstract should be a single paragraph.
Introduction needs to be rewritten. Delete the first two sentences are superfluous statements. Instead, you need to describe the tectonic framework of Iceland in a few sentences. Discuss previous research, the importance of direct measurements of crustal velocities, i.e. by refraction data, which models are relevant to the study region and what prompted this study. The near-surface velocity is dependent on crustal age, being significantly lower in volcanically active areas than in older, more eroded (Quaternary and Tertiary) formations. The RISE refraction profile (Weir et al. 2001) is the only model based on refraction data within your study area. Other profiles, such as SIST-SIL (Bjarnason et al., 1993) are east of the Reykjanes Peninsula. You need to explain where the models listed in Appendix 1 are located and you should indicate the location of these profiles in Figure 1.
Note also that you are using 1D models. Based on RISE the there is significant 2D structure within the upper crust along the Reykjanes Peninsula. The near-surface (0-3 km) velocity along the RP is poorly constrained in the 1D model by Tryggvason et al. 2002.
Figure 1 need to be redrafted showing local geology and tectonics.
2. Velocity models
Specify HOW the five velocity models are different and why?
The models in figure 2 vary with respect to velocity gradients, i.e. thickness of the upper crust. You should investigate how these variations in velocity gradients affect seismic wave propagation/ray bending depending on hypocentral depths.
Discuss trade-off between origin-time and hypocentral depth for different models.
Note that the VOG model is seemingly not based on refraction data from the Reykjanes peninsula. You need to use models based on refraction measurements within your study region, (Weir et al., 2001)
2.2. Your raypath reasoning is unclear, you need to model raypaths based on your velocity structure to explain what you mean by i.e. “flat rays”. See also raypaths modelled by Weir et al., 2001.
4. Discuss how your results match other Vp/Vs observations, i.e. Tryggvason et al. 2002, Weir et al 2001.
You need to evaluate your priory information properly prior to going into elaborate exercises evaluating models which do not apply directly to their study region. As a result your conclusions are not significant and reliable for other studies.
4 model correction scheme
I do not see the validity of this exercise as you do not evaluate its application to your earthquake data, nor do you explain how lowering the near-surface crustal velocities will affect your hypocentral depth locations. Rayleigh wave dispersion is not seemingly relevant for the local earthquake data your are presenting.
See attached manuscript with other comments.
-
AC1: 'Reply on RC1', Bohuslav Ruzek, 09 Jan 2024
Dear referee Nr.1.
thanks a lot for your review. I will read your comments more carefully and I will try to reflect your objections appropriately. However some of your points are questionable, at least from my view. E.g. including refraction measurements is not possible, since no new measurements are available to us. Weir et. al. processed only P-waves but, processing of earthquakes data needs to work simultaneously with both P- and S-wave velocity models. Including R-wave dispersion into classification of velocity models makes sense to me, it gives an independent degree of the model validity. (Measured) R-wave dispersion was adopted from an already published paper so no deeper details need to be repeated in the paper, as far as I can judge. The influence of the VOG model correction to the hypocenter localization is (briefly) discussed. Etc.
Nevertheless I believe that the topic may be insufficiently informative for a broader scientific community and publishing the paper in SE may not be beneficial for most of readers. Once again, big thanks for you for your effort.
With best wishes,
Bohuslav Ruzek
Citation: https://doi.org/10.5194/egusphere-2023-2465-AC1
-
AC1: 'Reply on RC1', Bohuslav Ruzek, 09 Jan 2024
-
RC2: 'Comment on egusphere-2023-2465', Simone Pilia, 08 Feb 2024
Dear authors,
Thank you for submitting your work to Solid Earth.
After carefully reviewing your manuscript and taking into account the feedback provided by Reviewer 1 (R#1), I am writing in my capacity as both a reviewer and editor.
Upon my reading of the article, I tend to be largely in agreement with the assessment from R#1 that the dataset, methods, and results presented in your manuscript do not deal with a significant advancement substantial enough to justify publication in Solid Earth.
It appears to me that your work may hold promise for a more specialised journal, although it currently falls short of meeting the standards of scientific excellence and innovation expected for publication in Solid Earth. I would encourage you to carefully consider the feedback provided and to explore opportunities for refining your research to potentially meet the criteria for publication in the future.
All the best,
Simone Pilia.
Citation: https://doi.org/10.5194/egusphere-2023-2465-RC2
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