Seismicity Before and After the 2023 M7.7 and M7.5 Turkey Quakes

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The objective of this paper is to study the seismicity before and after the 2023 M7.7 and M7.5 Turkey earthquakes. In particular, the earthquake catalogs were used; first, the reported seismicity transients during the pre-doublet-quake sequence were confirmed and then the post-doublet-quake sequence was investigated, considering physics-based and statistical approaches, to indicate that the two M6-class quakes were promoted by the doublet quakes.

This is an interesting and well-structured paper. All necessary sections (Introduction, Methods, Data, Results, Discussion). Moreover, the “Methods”, “Data” and “Results” sections are divided into sub-sections, providing additional details. In addition, all Figures and Diagrams are consistent with the analysis provided in the manuscript. However, some changes should be implemented, which will improve the paper. In particular:

Line 48: At the end of the first paragraph of the “Introduction” section, an additional brief paragraph should be added. This new paragraph should include a description of the geodynamic setting of the Anatolia-Aegean region. In particular, the major tectonic structures of this area should be mentioned (e.g. North Anatolian Fault Zone, Hellenic Subduction Zone, North Aegean Trough etc.). Moreover, the recent seismic events of the area should be highlighted, while is would be useful to mention the geodetic deformation pattern, related to the seismicity of this region. Typical papers, in which the corresponding information can be obtained and optionally be cited, are the following: 1. Hollenstein, C., Müller, M. D., Geiger, A., & Kahle, H. G. (2008). Crustal motion and deformation in Greece from a decade of GPS measurements, 1993-2003. Tectonophysics, 449(1–4), 17–40. https://doi.org/10.1016/j.tecto.2007.12.006, 2. Lazos, I., Chatzipetros, A., Pavlides, S., Pikridas, C. & Bitharis, S. (2020). Tectonic crustal deformation of Corinth gulf, Greece, based on primary geodetic data. Acta Geodynamica et Geomaterialia, 17(4), 413 - 424 Page 9391, 12(18), 9391. https://doi.org/10.13168/AGG.2020.0030, 3. Müller, M. D., Geiger, A., Kahle, H. G., Veis, G., Billiris, H., Paradissis, D., & Felekis, S. (2013). Velocity and deformation fields in the North Aegean domain, Greece, and implications for fault kinematics, derived from GPS data 1993-2009. Tectonophysics, 597–598, 34–49. https://doi.org/10.1016/j.tecto.2012.08.003. Please, apply.

Line 61: In this paragraph, I suggest adding more details, related to the geometry of seismic faults, such as strike, dip, rake etc. Please, apply.

Lines 123-125: Please, provide a more detailed description of the equations, included in these lines. Please, apply.

Lines 230-231: Please, explain why the USGS moment tensor solution was used. Have you tested the corresponding moment tensor solutions of other sources (e.g. GFZ, KOERI, BGS etc.)?

Line 407: I suggest renaming this section to “Discussion-Conclusions”. A “Conclusions” section is missing from the paper. Alternatively, this section can be divided into two parts; the “Discussion” section from Line 407 to Line 482, and the “Conclusions” section from Line 483 to Line 523. Please, apply.

Author Response

Comment 1. Line 48: At the end of the first paragraph of the “Introduction” section, an additional brief paragraph should be added. This new paragraph should include a description of the geodynamic setting of the Anatolia-Aegean region. In particular, the major tectonic structures of this area should be mentioned (e.g. North Anatolian Fault Zone, Hellenic Subduction Zone, North Aegean Trough etc.). Moreover, the recent seismic events of the area should be highlighted, while is would be useful to mention the geodetic deformation pattern, related to the seismicity of this region. Typical papers, in which the corresponding information can be obtained and optionally be cited, are the following: 1. Hollenstein, C., Müller, M. D., Geiger, A., & Kahle, H. G. (2008). Crustal motion and deformation in Greece from a decade of GPS measurements, 1993-2003. Tectonophysics, 449(1–4), 17–40. https://doi.org/10.1016/j.tecto.2007.12.006, 2. Lazos, I., Chatzipetros, A., Pavlides, S., Pikridas, C. & Bitharis, S. (2020). Tectonic crustal deformation of Corinth gulf, Greece, based on primary geodetic data. Acta Geodynamica et Geomaterialia, 17(4), 413 - 424 Page 9391, 12(18), 9391. https://doi.org/10.13168/AGG.2020.0030, 3. Müller, M. D., Geiger, A., Kahle, H. G., Veis, G., Billiris, H., Paradissis, D., & Felekis, S. (2013). Velocity and deformation fields in the North Aegean domain, Greece, and implications for fault kinematics, derived from GPS data 1993-2009. Tectonophysics, 597–598, 34–49. https://doi.org/10.1016/j.tecto.2012.08.003. Please, apply.

Response 1: According to this comment, we added a paragraph after the first paragraph of the “Introduction” (page 2). In this paragraph, we mentioned the major tectonic structures (e.g. North Anatolian Fault Zone, Hellenic Subduction Zone, North Aegean Trough etc.). We also highlighted recent events, showing the focal mechanism for each of these events (Figure 1). Moreover, we mentioned that the deformation associated with the doublet quakes can be treated as shear deformation (half-arrow pair) across the EAFZ. We deeply appreciated the reviewer’s recommendation to cite the three papers. However, we decided not to cite these papers because they mainly focused on the crustal deformation in and around Greece that is far from the EAFZ and because we thought that the crustal deformation in and around Greece was not directly associated with the doublet quakes.

 

Comment 2. Line 61: In this paragraph, I suggest adding more details, related to the geometry of seismic faults, such as strike, dip, rake etc. Please, apply.

Response 2: To address this comment, we added the geometry such as strike, dip, and rake for each the six segments (pages 5 and 6).

 

Comment 3. Lines 123-125: Please, provide a more detailed description of the equations, included in these lines. Please, apply.

Response 3: To address this comment, we provided a more detailed description of the equation (page 18).

 

Comment 4. Lines 230-231: Please, explain why the USGS moment tensor solution was used. Have you tested the corresponding moment tensor solutions of other sources (e.g. GFZ, KOERI, BGS etc.)?

Response 4: Thank you for the useful comment. In this study, we used the USGS moment tensor solutions, because we used the USGS fault models of the M7.7. and 7.5 quakes [2, 3] and considered consistency of the source between the moment tensor solutions and the fault models (page 6). However, we agreed with this reviewer’s comment. Therefore, we mentioned as follows (page 6): Our future research requires the use of the moment tensor solutions of not only the USGS but also other sources to strengthen the robustness of our findings. Examples include the moment tensor solutions reported by the KOERI (http://www.koeri.boun.edu.tr/sismo/2/moment-tensor-solutions/) and by the GFZ Helmholtz Centre for Geosciences (https://geofon.gfz.de/old/eqinfo/eqinfo.php).

 

Comment 5. Line 407: I suggest renaming this section to “Discussion-Conclusions”. A “Conclusions” section is missing from the paper. Alternatively, this section can be divided into two parts; the “Discussion” section from Line 407 to Line 482, and the “Conclusions” section from Line 483 to Line 523. Please, apply.

Response 5: According to this comment, we divided into two parts; the “Discussion” section (page 9) and the “Conclusions” (page 11).

Reviewer 2 Report

Comments and Suggestions for Authors

This is a carefully done study of interesting seismicity before and after the Turkey M7.7 and M7.5 earthquakes of February 2024. The authors mainly studied seismicity in the framework of ETAS and b-values, and also considered Coulomb stress modeling. The paper is well written and well organized.

The authors examined 3 earthquake catalogs and found similar results for all three. This suggests the results are not artifacts, or alternatively, increases the confidence of the results.

The abstract is clear and concise. The main result is that seismic activity increased 8 months before the two main earthquakes in a zone within 50 km radius of the mainshock epicenter. The seismic activity had distinctly low b-values. These areas were later shown to have high slip during the large events. The study was retrospective, so the zones of anomalies could not be identified in advance (a task (hope?) for later studies). Two later events of M6.4 and M5.9 were shown to have occurred where their activity was promoted by the slip during the large prior earthquakes..

Overall, a very nice paper and a welcome addition to the literature of this important earthquake doublet.

Author Response

Comment 1. This is a carefully done study of interesting seismicity before and after the Turkey M7.7 and M7.5 earthquakes of February 2024. The authors mainly studied seismicity in the framework of ETAS and b-values, and also considered Coulomb stress modeling. The paper is well written and well organized.

The authors examined 3 earthquake catalogs and found similar results for all three. This suggests the results are not artifacts, or alternatively, increases the confidence of the results.

The abstract is clear and concise. The main result is that seismic activity increased 8 months before the two main earthquakes in a zone within 50 km radius of the mainshock epicenter. The seismic activity had distinctly low b-values. These areas were later shown to have high slip during the large events. The study was retrospective, so the zones of anomalies could not be identified in advance (a task (hope?) for later studies). Two later events of M6.4 and M5.9 were shown to have occurred where their activity was promoted by the slip during the large prior earthquakes.

Overall, a very nice paper and a welcome addition to the literature of this important earthquake doublet.

Response 1: We thank the reviewer for this supportive comment.

 

 

Reviewer 3 Report

Comments and Suggestions for Authors

This study provides an important contribution to understanding seismic activity before and after the 2023 M7.7 and M7.5 Turkey earthquakes. The background and motivation are well articulated, and the integration of statistical and physics-based approaches is valuable. However, the manuscript would benefit from clearer language and more concise expression throughout manuscript. I consider the manuscript to be valuable, and further improvements are needed in terms of language clarity, formatting and figure presentation.

Here are specific suggestions:

Medium Comments：

1. To better illustrate the region’s seismotectonic setting, please incorporate the focal mechanisms of historical strong earthquakes into Figure 1. The caption for Figure 1 is not concise and clear enough. Please rewrite it. Please provide the names of the main faults in Figure 1. Line 39 mentions the Arabian and Anatolian tectonic plates; please indicate them on Figure 1. Also add Aegean Sea in the Figure 1. It is recommended to add an inset map to clearly show the tectonic region.
2. In Figure 2, it is suggested that the lines representing the 95% confidence intervals be displayed in a different color to distinguish them from the best-fit b-value curve. The current light red color is too faint; it is recommended to deepen the color to improve visibility.
3. The manuscript uses both 'quakes' and 'earthquakes' throughout. Please standardize the usage to one consistent term.
4. Please rewrite this paragraph to improve the logic of the language and the clarity of the research objectives of this paper.
5. L240: When calculating the b-value, why was a 50 km radius chosen? What is the actual width of the main fault? Please provide a reasonable and sufficient explanation in the main text.
6. L445-447: Please rephrase to enhance clarity and conciseness.

 

Comments for author File: Comments.pdf

Comments on the Quality of English Language

This is a valuable manuscript; however, improvements in clarity, conciseness, and flow of the language are necessary for publication. Therefore, I recommend a minor revision, focusing primarily on enhancing the language clarity and fluency.

Author Response

Comment 1. To better illustrate the region’s seismotectonic setting, please incorporate the focal mechanisms of historical strong earthquakes into Figure 1. The caption for Figure 1 is not concise and clear enough. Please rewrite it. Please provide the names of the main faults in Figure 1. Line 39 mentions the Arabian and Anatolian tectonic plates; please indicate them on Figure 1. Also add Aegean Sea in the Figure 1. It is recommended to add an inset map to clearly show the tectonic region.

Response 1: To address this comment, we incorporated the focal mechanisms of selected strong earthquakes into Figure 1a. We also rewrote the caption of Figure 1 and added the names of the main faults such as North Anatolian Fault Zone (NAFZ), Hellenic Subduction Zone (HSZ), North Aegean Trough (NAT), and so on. Moreover, we indicated the Arabian and Anatolian tectonic plates and the Aegean Sea in Figure 1. Based on the reviewer’s recommendation, we added a map (Figure 1a) to clearly show the tectonic region.

 

Comment 2. In Figure 2, it is suggested that the lines representing the 95% confidence intervals be displayed in a different color to distinguish them from the best-fit b-value curve. The current light red color is too faint; it is recommended to deepen the color to improve visibility.

Response 2: Thank you for the useful comment. To address this comment, we modified Figure 2 to improve visibility.

 

Comment 3. The manuscript uses both 'quakes' and 'earthquakes' throughout. Please standardize the usage to one consistent term.

Response 3: We thank the reviewer for this useful comment. We used “quakes” throughout.

 

Comment 4. Please rewrite this paragraph to improve the logic of the language and the clarity of the research objectives of this paper.

Response 4: We thank the reviewer for this useful comment. We are not sure which paragraph should be rewritten, because this comment does not indicate the corresponding paragraph. However, we tried to improve the language throughout and the clarity of the paper.

 

Comment 5. L240: When calculating the b-value, why was a 50 km radius chosen? What is the actual width of the main fault? Please provide a reasonable and sufficient explanation in the main text.

Response 5: To address this comment, we first pointed out that Kwiatek et al. showed seismicity transients: low b-values and seismic activation starting approximately 8 months before the 2023 M7.7 quake in the region within a 50 km radius surrounding the future M7.7 epicenter (page 6). Because our purpose was to confirm the previously-reported transient, we described that we used the same region to confirm the former transient (page 6). In response to another comment from the reviewer, we described the width of the main faults (segments 1 to 6) that we actually used in this study (pages 5 and 6).

 

Comment 6. L445-447: Please rephrase to enhance clarity and conciseness.

Response 6: Thank you for the useful comment. We rephrased to enhance the clarity and conciseness, as follows (page 10). “There is no doubt that the M7.7 quake was not the almighty quake [52], which would rupture an entire plate boundary at once and leave no stress that could produce any other kind of quake. To rephase it, the almighty quake is the extreme end of the characteristic earthquake behavior. The GR relation is the other end member of the spectrum.”

Reviewer 4 Report

Comments and Suggestions for Authors

In this paper, new and relative seismic data analysis software is used to analyze the characteristics of seismic activity changes before and after the 2023 double earthquake in Turkey, and the correlation of regional strong earthquakes from the perspective of seismic B-value and quake-induced Coulomb stress changes. The author further verifies the previous views and puts forward some new views on pre-earthquake activity sequence and post-earthquake aftershock duration. These new views are obviously of great reference value to better understand the characteristics of seismic activity before and after large earthquakes and to predict the risk of regional strong earthquakes.
I think there are still some details in the current article that need to be adjusted, mainly including the following.
(1) There is too much content in the "introduction" part of the article, but the "background of the research area" section is lacking. In fact, lines 49-91 of the introduction should fall under "Research Area Background." I suggest that the author should add "research area background" and simplify the introduction. In addition, the author needs to add a regional active tectonic map with reference to previous data, and express the current plate distribution, motion state and large boundary fault zones in the first paragraph of the introduction in the map.
(2) Some important information mentioned in the article, such as typical seismic events before and after the big earthquake in Turkey and earthquake cluster active areas in the region, should be fully expressed in the relevant maps, so as to further enhance the readability of the article.
(3) In the "results section", the contents that belong to the verification of previous studies (such as lines 237-253) can be refined as far as possible, so as to avoid repeating previous studies.
(4) In Figure 1, the location and scope of the cross section in Figure 6a, as well as the seismic rupture caused by early earthquakes in the region, should be marked. The locations of the 2023 M7.7 and 7.5 earthquakes and the 2020 M6.8 earthquakes should be indicated in Figure 7.
(5) Lines 355-361 should unify "eathquake" as "quake".
(6) The paper should have a "conclusion" section, and lines 483-523 should belong to the conclusion.

Author Response

Comment 1. There is too much content in the "introduction" part of the article, but the "background of the research area" section is lacking. In fact, lines 49-91 of the introduction should fall under "Research Area Background." I suggest that the author should add "research area background" and simplify the introduction. In addition, the author needs to add a regional active tectonic map with reference to previous data, and express the current plate distribution, motion state and large boundary fault zones in the first paragraph of the introduction in the map.

Response 1: Thank you for the useful comment. According to this comment, we added "research area background" (page 2) and simplify the “introduction” (page 1). We then added a regional active tectonic map to Figure 1. We next expressed the current plate distribution, plate motion, and large plate fault zones in the second paragraph of the introduction (pages 1-2) and Figure 1a.

 

Comment 2. Some important information mentioned in the article, such as typical seismic events before and after the big earthquake in Turkey and earthquake cluster active areas in the region, should be fully expressed in the relevant maps, so as to further enhance the readability of the article.

Response 2: We thank the reviewer for this useful comment. To address this comment, we showed the most recent five quakes with M7 or larger as typical seismic events in Turkey (Figure 1a), highlighting with the focal mechanism for each of these five quakes. We also showed locations of clusters C1, C2, C3, and C7 in Figure 1b.

 

Comment 3. In the "results section", the contents that belong to the verification of previous studies (such as lines 237-253) can be refined as far as possible, so as to avoid repeating previous studies.

Response 3: To address this comment, we refined the first paragraph of the section 5.1.1 to avoid repeating the previous study (page 6).

 

Comment 4. In Figure 1, the location and scope of the cross section in Figure 6a, as well as the seismic rupture caused by early earthquakes in the region, should be marked. The locations of the 2023 M7.7 and 7.5 earthquakes and the 2020 M6.8 earthquakes should be indicated in Figure 7.

Response 4: To address this comment, we described in the caption of Figure 1 as follows. “Segment 2 indicates the location and scope of the cross section in Figure 6”. To mark early earthquakes in and around the study region, we plotted earthquakes with M7 or larger during the period since 1904 in Figure 1a. In response to another comment from the reviewer, we indicated the locations of the 2023 M7.7 and 7.5 quakes and the 2020 M6.8 quakes in Figure 7.

 

Comment 5. Lines 355-361 should unify "eathquake" as "quake".

Response 5: We thank the reviewer for this useful comment. We used “quakes” throughout.

 

Comment 6. The paper should have a "conclusion" section, and lines 483-523 should belong to the conclusion.

Response 6: According to this comment, we divided into two parts: the “Discussion” section (page 9) and the “Conclusions” (page 11).