The Geological Structure and Tectonic Complexity of Northern Thessaly That Hosted the March 2021 Seismic Crisis

Round 1

Reviewer 1 Report

This review article deals with the seismotectonic characteristics of the 2021 earthquake sequence in northern Thessaly, and their connection with the area's older Alpine tectonics, addressing interesting alternative aspects of the local tectonic setting. It provides an integrated geological background for the whole epicentral area.

The manuscript is well-written with a good flow, although the latter requires a few changes. The authors provide a clear and quite detailed picture of the neotectonic setting and the Alpine geology and tectonics, which are important for their interpretations and conclusions. Perhaps a better clarification is needed for the inherited structures that participated in the 2021 sequence.

The authors collected and revised their own and other researchers' published works about the seismotectonic characteristics of the 2021 sequence, summing up, comprehensively, all the data and results. Interpretations, conclusions and posed questions are adequate and interesting. Few text relocations might be needed.

Some references are missing from published figures.

Specific attention should be paid in section 4.2 "The seismic faults". The comments are embedded in the attachment.

Another suggestion to improve the review is to add a brief discussion about the results of Kontoes et al. (2022) (ref No 76) must be added about the suggested seismic sources and their Coulomb stress results (the authors refer to this paper only for its InSAR results). The latter would be interesting to be compared with the results of Chatzipetros et al. (2021) and Kassaras et al. (2022) (from p 18, l 457 to p 19, l 464).

The manuscript has a good chance of reaching an excellent level. At present, the paper needs, in my opinion, a moderate revision, but it can be easily improved if the authors follow at least the most important comments.

Further comments-corrections are embedded in the attached file.

Comments for author File: Comments.pdf

Author Response

We sincerely thank the reviewer for his well-intended review.

We followed almost all suggestions, besides some rearranging in the text. The latter is taken into account and we made rearrangements that we thought would much improve the flow.

The manuscript has taken a new form with the addition of new figures as well.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors revised previous findings on the northern Thessaly tectonics based on recent (2021) earthquakes, and indicate blind unknown faults as the cause for the recent seismic events. I recommend this paper for publication after a minor revision.

Line 38. The sentence is either unfinished (something missing at the end) or there is one "and" at the end that should be deleted: "in the surrounding area and."

Line 56: Did the authors mean to say "DO the older, ‘inherited’ structures still define.." instead of "are the older, ‘inherited’ structures still define"?

If possible, Fig. 4 should have a better resolution.

Line 163: Did the authors mean to say :"Older Palaeozoic structures are not recognized"? or "Older Palaeozoic structures can not be recognized" or "We did not recognize older Palaeozoic structures"? Please rephrase.

Line 472. Did the authors mean to say "Moreover, IT IS close"?

Lines 472 to 475. Please rephrase the interrogative sentences similar to what you did in line 485 (Then the question arrives:), or add a sentence before them. For example, "However, what remained uncertain was the following. Did the previous..."

Line 485. Perhaps it is better to say Then the question ARISES?

Lines 488-489: Is this sentence finished? It seams that something is missing at the end. Should this sentence even be here, it looks out of place?

Author Response

We thank reviewer #2 for his fruitful comments. They definitely improved the manuscript.

The comment/reply part follows below.

Comment:

Line 38. The sentence is either unfinished (something missing at the end) or there is one "and" at the end that should be deleted: "in the surrounding area and."

Reply:

Done.

Comment:

Line 56: Did the authors mean to say "DO the older, ‘inherited’ structures still define.." instead of "are the older, ‘inherited’ structures still define"?

Reply:

Done.

Comment:

If possible, Fig. 4 should have a better resolution.

Reply:

We tried to better process the published image. Unfortunately, the original design is lost and the publication is quite old (1991).

Comment:

Line 163: Did the authors mean to say :"Older Palaeozoic structures are not recognized"? or "Older Palaeozoic structures can not be recognized" or "We did not recognize older Palaeozoic structures"? Please rephrase.

Reply:

Done.

Comment:

Line 472. Did the authors mean to say "Moreover, IT IS close"?

Reply:

Done.

Comment:

Lines 472 to 475. Please rephrase the interrogative sentences similar to what you did in line 485 (Then the question arrives:), or add a sentence before them. For example, "However, what remained uncertain was the following. Did the previous..."

Reply:

Done.

Comment:

Line 485. Perhaps it is better to say Then the question ARISES?

Reply:

Done.

Comment:

Lines 488-489: Is this sentence finished? It seams that something is missing at the end. Should this sentence even be here, it looks out of place?

Reply:

Done.

Reviewer 3 Report

The merit of this work is the deep and wide knowledge of the area under study and the related problems. The language is understandable and clear and the english on average correct. However, the work presents numerous problems related to both the structure of the text and the substance of the study. Therefore, it needs more revisions before publication. General questions are given below, while more detailed questions are given in the pdf text.

First of all, I am not sure if this work is suitable for Geotechnics journal, since the subject matter is not within the scopes of the magazine.

In general, the aims of this work, which would be to identify the tectonic structures, possibly responsible for the seismic events under study and to help resolve the question about the current stress field in the area, are not well supported by adequate data and by a personal and innovative analysis. In fact, there are no new structural, geophysical or geodetic data, but only a literature review. As for the data, the only innovative data seem to be the seismic-induced effects (photos of which are reported, pure observations, and the position on the map) that can help determine the fault that moved during a seismic event. However, the use of these effects must take into account many factors, since their distribution in the epicentral area is strongly influenced by local conditions. Eg. if there is an alluvial basin (in which, usually, there are favourable conditions for liquefaction) stretched in the WNW-ESE direction, the liquefaction phenomena will occur inside it, thus also distributing along this direction, but this does not mean that there is a fault along that alignment. The same thing applies to the presence of large slopes subject to instability.

Furthermore, the data discussed is not sufficient to give an in-depth source model. It is not possible to define the geometry of the fault plane in depth and to draw into question models of detachment and bifurcation only considering fresh and new slickensides (which I also do not see). The expression of a fault on the surface can be very different from that in depth, also considering the different rheological conditions, in depth, and the role of stratigraphy on the surface.

In this regard, I would suggest using instrumental seismicity data to model the faults in depth. If the 2021 seismic sequence has been recorded, it is possible to obtain a global view of the seismogenic volume and to draw out the structures three-dimensionally. If these data are available, I can suggest experts in the sector, such as the PhD Bruno Pace of the University of Chieti (Italy), whose contact details and publications are available on the web.

The complex tectonic setting that the Authors reconstruct is not supported by sufficient and adequate data, see comment below.

Stress field change is poorly supported. The Authors reassess the stress field on the basis of focal solution (not their analysis) and orientation of the ground fracture. The use that the Authors can do of the ground rupture depends on the type of rupture; since these fractures are related to liquefaction and ground instability the Authors cannot use them like stress indicator. The fresh and new slickensides are not visible in the pictures; those showed seem to be old features.

If the Authors assent that the extensional tectonic phase P3 is active until Today, why do they surprise of the focal solutions of the 2021 seismic sequence? Additionally, the observed contraction (figure 7) is very poor compared to extension and it could be a residual stress.

As regards the organization of the text, there is no a tidy structure: the method and the results are not reported, it is not clear what type of analysis is carried out, the method used and the (new) data processed.

In the text there is too much description of ancient Alpine geology, stratigraphy and tectonics and little of neotectonics. These data are superfluous for active tectonics studies, this part can be shortened and the description of active tectonics should be deepened.

The title reports about geological structure and tectonic complexity, but there are not geological nor structural analyses in this work. Maybe the title should report “seimsogeological effects” that are the only novel issue.

The abstract does not explain the method used, the data processed and the results obtained. Reading the whole text, it is clear that the work aims to find the seismogenic faults, but tectonic, seismotetonic, active tectonic studies are not done, rather previously published bibliographic data are discussed in the work.

Tyrnavos and Larissa faults merit to be described in depth, they are more important than the alpine-age features. Why are they considered active? What the active tectonics studies said?

The profiles showed in figure 5 don't intercept the Titarissisos fault, but maybe its westward prosecution, please clarify this issue. Can the showed faults be the westward prosecution of the Titarissios fault? However, the base of the Quaternary deposits seems to be not dislocated and the faults sealed.

The authors could make better use of the InSAR analysis images by comparing the faults obtained from this analysis with those known from the literature, such as the Titarissisos fault.

The source models proposed by authors from literature should be shown in a figure to help the authors to understand the seismotectonic frame.

As it regards the active faults likely associated to the seismic events, the Authors advance the hypothesis that ancient (alpine age) compressional structure could be reactivated as normal faults. It is likely, but there are not thrusts reported in any map and the data supporting this hypothesis are neither sufficient nor adequate. It is difficult to understand this issue.

The possibility that the activated structures are accommodation structures of the Titarissios fault or a sympathetic fault is interesting but there is a lack of figures and models to support this evidence.

The other hypothesis is that the faults are blind (as many authors claim) but I see in the map some WNW -ESE trending normal faults which therefore have a geometry and kinematics compatible with the events of 2021. Because these faults are not taken into consideration? Wouldn't it be interesting to model them since their compatibility with the seismic sequence?

In general, I don’t see great tectonic complexity, the focal solutions of the entire seismic sequence are coherent each other and they well match (as it regards direction, geometry and kinematics) with the faults mapped in the study area.  

Figures should by improved: their quality is poor; the text is not readable and many figures have been taken from published papers thus worsening their quality.

Comments for author File: Comments.pdf

Author Response

Reviewer 3

General reply:

It is obvious that the reviewer did not understand the purpose of this paper, probably because he/she didn’t know where this article was meant to be published. As a review paper aiming at contributing to a Special Issue dedicated to the 2021 seismic sequence with a predetermined structure, the scope is to address the geological setting of the 2021 epicentral area, the role of the older structures in the modern tectonic setting and the 2021 sequence, the presentation of the proposed tectonic features of the sequence, and the discussion of alternative interpretations and opening of new concerns about the earthquakes’ tectonic setting. Other aspects of the seismic sequence (e.g. remote sensing, seismological analysis, engineering seismology, etc.) will be discussed by the other articles in the same Sp. Issue. For this reason, no new data, methods or results are addressed here, but we give emphasis on our previously published results in other journals. As a consequence, some of the reviewer’s comments were intentionally skipped because they would alter the essence and purpose of our article.

Many of the comments, however, which were very constructive and to the poin, were followed, and they definitely improved the manuscript. Some of them coincided with the other two reviewers’ comments. For this reason, we would like to specially thank the reviewer.

As it can be seen bellow, we tried to deal with all comments individually.

Comment:

First of all, I am not sure if this work is suitable for Geotechnics journal, since the subject matter is not within the scopes of the magazine.

Reply:

This paper is intended to be published in a special issue dedicated to the 2021 earthquake sequence in northern Thessaly based on a predetermined structure with a group of articles including a paper (our paper) about the geology, both alpine and post-alpine, of the study area, giving emphasis to the alpine tectonics and neotectonics as well as the seismotectonic setting of the sequence. Besides this type of ‘general’ information, we strongly believe that ‘old’ tectonics in alpine geology played a significant role in the seismic sequence. Therefore, we had to expand the manuscript in this direction.

Comment:

In general, the aims of this work, which would be to identify the tectonic structures, possibly responsible for the seismic events under study and to help resolve the question about the current stress field in the area, are not well supported by adequate data and by a personal and innovative analysis. In fact, there are no new structural, geophysical or geodetic data, but only a literature review. As for the data, the only innovative data seem to be the seismic-induced effects (photos of which are reported, pure observations, and the position on the map) that can help determine the fault that moved during a seismic event. However, the use of these effects must take into account many factors, since their distribution in the epicentral area is strongly influenced by local conditions. Eg. if there is an alluvial basin (in which, usually, there are favourable conditions for liquefaction) stretched in the WNW-ESE direction, the liquefaction phenomena will occur inside it, thus also distributing along this direction, but this does not mean that there is a fault along that alignment. The same thing applies to the presence of large slopes subject to instability.

Reply:

This paper aims at not providing new data; it is a review paper also based in our results previously published. Toward this end we do not analyze in detail the data that we have found in previous publications; instead, we summarize our previous findings and put them together with other previously published works which are properly discussed in the Discussion section. It was also important for us and the scope of this article to present all previously published interpretations for the tectonic setting of the sequence, emphasizing, of course, to ours. However, the reviewer has a good point that we do not clearly identify the tectonic structures related to the sequence, an issue also addressed by another reviewer; this issue has been taken care of. Concerning the possible gravitational, or secondary ground ruptures, the reviewer correctly marks their misinterpretation as primary ruptures. As we better explain it now in the manuscript, we suggest that not all the ruptures are primary, but if we also consider other information that pre-existed the earthquakes (e.g. the borehole network that revealed the occurrence of very recent faulting beneath the soil and under specific ruptures) we are almost entirely convinced that these specific ruptures are primary.

Comment:

Furthermore, the data discussed is not sufficient to give an in-depth source model. It is not possible to define the geometry of the fault plane in depth and to draw into question models of detachment and bifurcation only considering fresh and new slickensides (which I also do not see). The expression of a fault on the surface can be very different from that in depth, also considering the different rheological conditions, in depth, and the role of stratigraphy on the surface.

Reply:

We disagree that the data discussed are not sufficient to give a SIMPLE NUMERICAL MODEL. As the reader will see, the methodology of all models proposed by other researchers do not differ significantly from ours. Moreover, our model has been previously published in peer-reviewed journal without any methodological doubt. We strongly believe that we had in our inventory enough elements to INFER, not to prove, the specific setting. We agree that rupture propagation may vary from the focus and upwards, but how much of variation can be accommodated? We do not infer a science-fiction model. This issue has been also addressed in another publication of ours in another peer-reviewed journal.

Comment:

In this regard, I would suggest using instrumental seismicity data to model the faults in depth. If the 2021 seismic sequence has been recorded, it is possible to obtain a global view of the seismogenic volume and to draw out the structures three-dimensionally. If these data are available, I can suggest experts in the sector, such as the PhD Bruno Pace of the University of Chieti (Italy), whose contact details and publications are available on the web.

Reply:

First of all, we did not intend to determine any fault model in this paper. We used a model of ours previously published and we also cite the models of other research groups. Perhaps we did not make it clear in the text that we used bibliographic data; we fixed that. We also agree with the reviewer that we did not provide sufficient information about our preferred model, a problem also fixed. Concerning the 3D modelling, we present here our previously published simple numerical model, a most common form of model found in a plethora of articles, that facilitates the Okada and Coulomb calculations. For this reason, we exploited focal mechanisms, the hypocentral depth, the spatiotemporal aftershock distribution, the surficial ruptures. We added an explanatory text in the manuscript in the corresponding section. We also tested our model using the Okada formulae to compare the modelled deformation with the InSAR deformation. Although these were the subject of our previous work, for the purpose of this review article we make a proper reference.

We would also like to thank the reviewer for his recommendation, but we do not intend to carry out new research in this paper. The geophysical model is in our intentions for a future article.

Comment:

The complex tectonic setting that the Authors reconstruct is not supported by sufficient and adequate data, see comment below.

Stress field change is poorly supported. The Authors reassess the stress field on the basis of focal solution (not their analysis) and orientation of the ground fracture. The use that the Authors can do of the ground rupture depends on the type of rupture; since these fractures are related to liquefaction and ground instability the Authors cannot use them like stress indicator. The fresh and new slickensides are not visible in the pictures; those showed seem to be old features.

Reply:

The stress field POSSIBLE change, or perhaps variation, can be inferred from the focal mechanisms alone, why shouldn’t it be? Two strong earthquakes occurred, and several smaller, sufficient aftershocks were recorded to provide safe results. Thus, all proposed foci from a variety of institutes showed the same thing. Why shouldn’t we trust them? As mentioned before, we explain and suggest that not all ground ruptures were gravitational. Concerning the slickensides, the reviewer correctly marks a misunderstanding caused in the manuscript. Fresh ruptures were observed in the soil over the alpine basement. What we found was faulting, obviously reactivated with different kinematics than the alpine one, which matches the faulting of the 2021 sequence. The InSAR images clearly mark the maximum deformation in this particular area of the alpine basement with the fringes pattern indicating NW-SE rupturing. Thus, we have many reasons to believe that the local stress field is not the one we used to know (NE-SE oriented with E-W faulting). We do not talk in the paper about a severe change, but a diversion of the extension direction.

Comment:

If the Authors assent that the extensional tectonic phase P3 is active until Today, why do they surprise of the focal solutions of the 2021 seismic sequence? Additionally, the observed contraction (figure 7) is very poor compared to extension and it could be a residual stress.

Reply:

Without any doubt, the P3 phase is not similar to the moment tensors. As we mention in the text, the moment tensors are similar to the P2 phase. We think that their difference is obvious; that is why Caputo & Pavlides (1993) proposed two different extension tectonic phases (P2 and P3; Fig. 6). Thus, instead of getting moment tensor solutions similar to the active P3 phase, we got ones similar to the previous P2 phase, which is a surprise.

Comment:

As regards the organization of the text, there is no a tidy structure: the method and the results are not reported, it is not clear what type of analysis is carried out, the method used and the (new) data processed.

Reply:

As a review paper, there are no new methods and results to report. Our aim was to make the synthesis of all published data (including and emphasizing ours), to suggest alternative interpretations and to address new questions for future research. However, some flow problems are fixed, and improved descriptions and explanations are added as another reviewer also suggested.

Comment:

In the text there is too much description of ancient Alpine geology, stratigraphy and tectonics and little of neotectonics. These data are superfluous for active tectonics studies, this part can be shortened and the description of active tectonics should be deepened.

Reply:

Alpine tectonics played a role as inherited structures in the 2021 sequence, thus it is properly discussed in the manuscript. Finding faults of the same geometry and kinematics in the alpine formations as well, we had to describe them as well. Therefore, the alpine geological background had to be presented. This part was also important for the purposes of the Special Issue.

Comment:

The title reports about geological structure and tectonic complexity, but there are not geological nor structural analyses in this work. Maybe the title should report “seimsogeological effects” that are the only novel issue.

Reply:

As the reviewer says we present the geological structure; we do not perform geological analysis. We also strongly believe that our suggestions for the possible occurrence of an underlying detachment-type fault, the split rupture propagation, the role of the inherited structures, and the fault segment triggering are a matter of geological and tectonic complexity.

Comment:

The abstract does not explain the method used, the data processed and the results obtained. Reading the whole text, it is clear that the work aims to find the seismogenic faults, but tectonic, seismotetonic, active tectonic studies are not done, rather previously published bibliographic data are discussed in the work.

Reply:

As mentioned above, this is a review article, providing an integrated view of the study area, and alternative aspects and concern.

Comment:

Tyrnavos and Larissa faults merit to be described in depth, they are more important than the alpine-age features. Why are they considered active? What the active tectonics studies said?

Reply:

The related literature is very rich for these faults. Focused multidisciplinary investigations have been performed mostly by Caputo et al., and collective, summarized descriptions with activity assessment have been adequately presented in Caputo et al. (2012) paper and GreDaSS (Greek Database of Seismogenic Sources) which are both cited. Giving here one more extensive description would be like repeating the aforementioned article once more. Moreover, none was (re)activated during the 2021 sequence, so why should they “deserve” so much attention? Thus, we just gave a short report of what we think is important for the purpose of this paper.

Comment:

The profiles showed in figure 5 don't intercept the Titarissisos fault, but maybe its westward prosecution, please clarify this issue. Can the showed faults be the westward prosecution of the Titarissios fault? However, the base of the Quaternary deposits seems to be not dislocated and the faults sealed.

Reply:

We made it clearer.

The original report says that the fault displaces the Villafranchian sediments.

Comment:

The authors could make better use of the InSAR analysis images by comparing the faults obtained from this analysis with those known from the literature, such as the Titarissisos fault.

Reply:

We gave priority to our previously published InSAR analysis which clearly matched the coseismic ruptures on the Zarkos Mt. We also added a new map-figure to show it better.

Comment:

The source models proposed by authors from literature should be shown in a figure to help the authors to understand the seismotectonic frame.

Reply:

We added a synthetic map-figure with our findings and, of course, our source model. Putting all models and/or all published deformational features in one figure, it would make it hard to read. We also think that it wouldn’t attach importance to the comprehension of the epicentral area; all important differences have been discussed in the text. Moreover, many papers do not provide the necessary parameters to plot the sources correctly on a map.

Comment:

As it regards the active faults likely associated to the seismic events, the Authors advance the hypothesis that ancient (alpine age) compressional structure could be reactivated as normal faults. It is likely, but there are not thrusts reported in any map and the data supporting this hypothesis are neither sufficient nor adequate. It is difficult to understand this issue.

Reply:

This is the reason for being so descriptive in the Alpine geology/tectonics. Schistosity in this area is an indicator of the presence of compressional tectonics. Perhaps there is also a thrust that might have not been mapped before.

Comment:

The possibility that the activated structures are accommodation structures of the Titarissios fault or a sympathetic fault is interesting but there is a lack of figures and models to support this evidence.

Reply:

We cannot prove it, and we don’t, but we can suggest it, based on our considerations (which are adequate).

Comment:

The other hypothesis is that the faults are blind (as many authors claim) but I see in the map some WNW -ESE trending normal faults which therefore have a geometry and kinematics compatible with the events of 2021. Because these faults are not taken into consideration? Wouldn't it be interesting to model them since their compatibility with the seismic sequence?

Reply:

As we mentioned before, the purpose of this paper is not to carry out new research and search for new results. We present what is evidence and we suggest what can be inferred. We feel less confident in supporting such a consideration.

Comment:

In general, I don’t see great tectonic complexity, the focal solutions of the entire seismic sequence are coherent each other and they well match (as it regards direction, geometry and kinematics) with the faults mapped in the study area. 

Reply:

Concerning tectonic complexity, this issue has been replied above.

Comment:

Figures should by improved: their quality is poor; the text is not readable and many figures have been taken from published papers thus worsening their quality.

Reply:

The figures’ quality is downgraded in the pdf provided by the editorial office probably for copyright reasons. Almost all figures are of high resolution with only one exception of a figure from an old publication (which soever has been improved).

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Given that the Authors clarify that this paper is a review manuscript written under invitation for a Special Issue dedicated to the 2021 seismic sequence, I understand many issues that I disapproved before.

However, some issues remain at odds with my opinion.

As for an example, many of the coseismic effects are not evident in the pictures, such as rockfalls. What I see in the pictures are old slikenlines on the fault plane, not fresh coseismic. However, if these data come from literature, I accept them.

That of slikenlines is a hard issue. Slikenlines are considered as fresh coseismic effects and insert into 4.1. Ground deformation phenomena paragraph. However, in the conclusion they are neotectonically formed slickensides. I am confused! Are they produced by the 2021 seimsic sequence?

I still believe that it is superfluous to devote more than half of the article to the description of Alpine tectonics but above all to its sediments. I would have appreciated a discussion regarding active tectonics. I agree that the Alpine geological and tectonic framework is necessary, but I believe that the fact that this is so thorough and takes up half the article is superfluous.

I strongly disagree with these sentences:

-          “This direction is not unfamiliar in the broader area as it used to be the dominant direction during the previous tectonic phase (P2, Figure 67; [9]). Moreover, it is close to the late alpine, compressional P1 tectonic phase (Figure 67; [9]) that caused the NNW-SSE-striking thrusts in the region.” How can an extensional phase (P2) to be close to a compressional one? Additionally, where the NNW-SSE-striking thrusts are? They play an important role as likely reactivated structures. One of the main questions is: Can formerly thrust alpine faults be reactivated as normal during the afterward extension? but I don’t see these thrusts in any figure.

-          “Line 716: The InSAR images, along with the observation of fresh and neotectonically formed slickensides on old shear zones of the gneiss and schist comprising alpine basement suggest a second possible rupturing path…. “Second respect to what???

-          Line 716-721 the sentence is not clear.

-          Line 725: The Zarkos blind fault can be considered as the emerged seismogenic source. What is the meaning of “emerged” if it is blind????

If the Titarissios fault (yellow arrows in Figure 1) had been previously mapped but never studied, you can map it rather that indicate by arrows. However, you should propose its study in future.

Some small comments are reported in the text

I do not appreciate some structural aspects of this work, but it is a subjective opinion that does not preclude the possibility that the manuscript will be published, perhaps after having clarified the aspects discussed above. In light of the above, I believe this manuscript is ready for publication after minor revisions.

Comments for author File: Comments.pdf

Author Response

General reply:

We thank the reviewer once again, first of all, for his understanding of the type and aim of our paper. Concerning the new comments, some are probably confused by the too many changes in the revised edition. These are usually clarified since the first round of review.

However, some are important, and they definitely improve the manuscript.

Last, but not least, we thank the reviewer for his very thorough overall review. If it weren’t for that, our work wouldn’t have been improved as it has been improved now.

We provide a reply to each of the comments below. We also took into consideration the few remarks in the pdf file.

Comment:

As for an example, many of the coseismic effects are not evident in the pictures, such as rockfalls. What I see in the pictures are old slikenlines on the fault plane, not fresh coseismic. However, if these data come from literature, I accept them.

Reply:

Figure 12 shows some examples of rockfalls. The phenomenon was not very intense and broad, but it was locally observed in the places marked in the inset (a) of figure 12.

As of the slickenlines, indeed these are old, not of alpine, but of post-alpine age. We made it clearer in the manuscript after the reviewer’s well-aimed comment in the first round.

Comment:

That of slikenlines is a hard issue. Slikenlines are considered as fresh coseismic effects and insert into 4.1. Ground deformation phenomena paragraph. However, in the conclusion they are neotectonically formed slickensides. I am confused! Are they produced by the 2021 seimsic sequence?

Reply:

As also replied above, we quote this specific part:

“Indeed, slickenlines of normal dip-slip movement were observed on N160°E-striking, moderately dipping (~50° average), polished surfaces (Figure 10d,e), as well as cataclasite and micro-fractures, implying the neotectonic reactivation of a pre-existing shear zone in brittle conditions.”

What we state in this sentence is that we found slickenlines of neotectonic age, not necessarily created by the last 2021 earthquake, but by former episodes of the same tectonic phase.

Comment:

I still believe that it is superfluous to devote more than half of the article to the description of Alpine tectonics but above all to its sediments. I would have appreciated a discussion regarding active tectonics. I agree that the Alpine geological and tectonic framework is necessary, but I believe that the fact that this is so thorough and takes up half the article is superfluous.

Reply:

The description of Alpine tectonics and how it contributed to the 2021 seismotectonic setting is what was missing in all published papers. No one has made the connection between these two distant regimes, and hence, this is what we try to emphasize.

Comment:

I strongly disagree with these sentences:

-          “This direction is not unfamiliar in the broader area as it used to be the dominant direction during the previous tectonic phase (P2, Figure 67; [9]). Moreover, it is close to the late alpine, compressional P1 tectonic phase (Figure 67; [9]) that caused the NNW-SSE-striking thrusts in the region.” How can an extensional phase (P2) to be close to a compressional one? Additionally, where the NNW-SSE-striking thrusts are? They play an important role as likely reactivated structures. One of the main questions is: Can formerly thrust alpine faults be reactivated as normal during the afterward extension? but I don’t see these thrusts in any figure.

Reply:

We refer to the stress direction which can create faults of the same strike, but of entirely different kinematics. Thus, a reverse of the stress field can easily be related to faults of a similar direction.

The geological map of Figure 1 shows the major overthrusting in the area between major lithological units. Each lithological unit has undergone an intense inner deformation as the next two figures show forming a network of thrusts and folds impossible to be drawn on the map. However, the fault lines, possibly recognized as photogrammetric lineations in the geological map of IGME, were probably easier to be detected and mapped in the 1:50,000 scale.

Comment:

-          “Line 716: The InSAR images, along with the observation of fresh and neotectonically formed slickensides on old shear zones of the gneiss and schist comprising alpine basement suggest a second possible rupturing path…. “Second respect to what???

Reply:

Now Line 641: First of all we already rephrased the sentence deleting “fresh” from the characterization of the slickenlines. After this successful comment, the sentence is rephrased as:

“The InSAR images, along with the observation of neotectonically formed slickensides on old shear zones of the gneiss and schist comprising alpine basement, suggest a main rupturing path during the first major event with a possible secondary and steeper one aiming at the Titarissios valley.”

Comment:

-          Line 716-721 the sentence is not clear.

Reply:

See the reply above.

Comment:

-          Line 725: The Zarkos blind fault can be considered as the emerged seismogenic source. What is the meaning of “emerged” if it is blind????

Reply:

We improved the sentence as the rupture reached very close to the surface.

Comment:

If the Titarissios fault (yellow arrows in Figure 1) had been previously mapped but never studied, you can map it rather that indicate by arrows. However, you should propose its study in future.

Reply:

We chose this kind of mark due to the fact that we do not know how accurate and by which method was this fault mapped to all its extent. Explanation was added in the text as well.

Comment:

I do not appreciate some structural aspects of this work, but it is a subjective opinion that does not preclude the possibility that the manuscript will be published, perhaps after having clarified the aspects discussed above. In light of the above, I believe this manuscript is ready for publication after minor revisions.

Reply:

We tried to distinguish data and measurements from interpretations so that the reader will value what he needs from our work. We also do not agree with the interpretations of other researchers, but it is their point of view which worth our respect. And that’s the beauty of science.