Review report by Enrico Tavarnelli for manuscript n. se-2021-29 by Dario Zampieri, Paola Vannoli and Pierfrancesco Burrato titled: “Geodynamic and seismotectonic model of a long-lived transverse structure: The Schio-Vicenza Fault System (NE Italy)”, submitted to Solid Earth.

To the SE Editor, Prof. Beatrice Magnani

Dear Beatrice,

            This paper provides a new and original documentation of the structural history and seismotectonic evolution of a long-lived transverse lineament, the Schio-Vicenza Fault System, that dissects the thrust front of the Southern Alps in the Veneto sector of the Adria foreland microplate in NE Italy. This is achieved through a detailed and genuinely multidisciplinary approach, that integrates field mapping, stratigraphic investigation, structural analysis, seismic profile interpretation, current and historical seismicity, coupled with a wealth of data from a wide literature in the region. The topic dealt with in the study is of great interest to anyone that has an interest in understanding the evolution of the Southern Alpine system and in constraining the seismotectonic potential of the area. Moreover, the study illustrates an example of applicability of universal concepts of fault reactivation and structural inheritance under a 3D view, with emphasis on the interaction of strike-slip systems at triple junctions. These topics have generated a lively debate, and the submitted manuscript sheds new light in this direction, providing a very well-documented case. The Authors’ interpretations are consistent with the data presented, and the original “zipper model” proposed to account for strike-slip reversals is very convincing.

            The manuscript is well written and well organised, with English and presentation forms that are overall very good. The illustrations and tables are all clear, legible and very much informative (but see my separate comment to Fig. 2). The quality of the contribution, in all its parts, is overall high. Good credit is given to the existing literature, both methodological and regional. However, I believe that the manuscript would benefit from a slight extension of the reference list, with citation of a few papers that are listed separately in this review report. Unfortunately, part of the suggested missing references happen to arise from my own research, and in general I am quite reluctant to self-advertise my work amongst colleagues. But the submitted manuscript refers to topics where my collaborators and I have long worked and published; thus I believe that a slight extension of the reference list with inclusion of the mentioned contributions would be highly beneficial for the reader with field examples in thrust belts that laterally flank the South Alpine chain.

            I found this an extremely stimulating contribution and believe that it will make a very interesting title for a genuinely international and multidisciplinary audience. It is my opinion that the manuscript may be accepted for publication almost as it stands, with only the incorporation of a few sentences (with related references listed below), and the insertion of minor alterations to the text for the sake of an improved legibility. Therefore, I recommend without reservations that this manuscript is accepted for publication on Solid Earth only pending on minor suggested revisions, that are listed separately.

I require no anonimity and wish that all my comments are forwarded to the Authors. I hope that my review is received as a constructive and supportive indication, that may assist the Authors to achieve an even more suitable and documentally supported paper, and the Editor in formulating a final, positive decision in the interest of Solid Earth and of its wide, international readership.

NOTE - Comments and suggestions on how to improve the current version of the submitted manuscript are listed separately in the .pdf document attached to my review report.

                       Siena, Italy, 24 May 2021

                                                                                 Sincerely,

Enrico Tavarnelli

Review report by M. Eliana Poli for manuscript “Geodynamic and seismotectonic model of a long-lived transverse structure: The Schio-Vicenza Fault System (NE Italy)” by D. Zampieri, P. Vannoli, P. Burrato. 

Solid Earth (se_2021_29).

The manuscript focuses on the deformative history of the Schio-Vicenza fault-system, one of the most complex transverse structure that separates the eastern Southalpine chain and its foreland, from the Lessinean block (i.e. the weakly deformed Apennine foreland).

The work is well organized and represents an important contribution in order to understand the seismotectonic of the Southern Alps.  English language is always appropriate.

After a wide and thought analysis of the previous works, the Authors deepen the historical and instrumental seismicity of the area under examination. 

The Authors collected all the available geological, geophysical, morphological data in order to devise a detailed kinematic picture of the tectonic evolution of the SVF, clearly highlighting the main problems of interpretation.

The new proposed kinematic model resolves the apparent interpretative discrepancies but, in my opinion, the Authors do not discuss adequately the consistence between the new structural model and the present geodynamic setting of the eastern Southern Alps (i.e.  the present indentation and counterclockwise rotation of Adria). In other words: is the proposed “opening zipper model” consistent with the kinematic setting of the Southalpine indenter? (for details see the attached file).

Figures: in the present form, they are not always easily legible. Please, when possible, enlarge them (see the attached pdf).

In short, the work is certainly an excellent starting point for every tectonic study of the Southern Alps and I recommend the publication on Solid Earth but after some minor revisions.

Accurate observations in the .pdf attached file.

Best regards

Maria Eliana Poli

Review of the manuscript „Geodynamic and seismotectonic model of a long-lived transverse structure: The Schio-Vicenza Fault System (NE Italy)“ by Dario Zampieri, Paola Vannoli and Pierfrancesco Burrato

This review manuscript starts out with a revision of the literature about the Schio-Vicenza fault since the beginning of geologic investigations in the area. Then the available evidence on present-day activity along the faualt and the neighbouring areas is reviewed. It then presents a few geologic data, mainly on the foundation of previous work of the first author, and again from recently published work. In the discussion, the authors apply two models on the Schio-Vicenza fault: (1) A „zipper“ model on its northern part, (2) and a model of transtension on its southern part.

In the end, the authors conclude that the Schio-Vicenza fault is an inherited Mesozoic fault and that this fault and potential other parallel faults in the subsurface of the foreland basins present a potential earthquake hazard.

While the manuscript is generally written in good English, there are some phrasing problems. I am not a native speaker, but neverteless made a few annotations in the manuscript. The review paper arrives at significant conclusions regarding the earthquake risk in the area. It is well suited for publication and within the scope of this journal. I suggest publication after minor to major revision, and hope that my comments help to improve the manuscript. 

Problems

In their conclusions, the authors arrive at an indenter model in which the Adriatic plate indents Eurasia in the eastern Southern Alps. However, in previous studies it has been shown, that the „main indentation“ in the eastern Southern Alps is delimited by the Giudicarie fault and the Pustertal-Gailtal fault (Ratschbacher et al., 1991; Reiter et al., 2018; Rosenberg et al., 2004; Rosenberg et al., 2007). This concept is neither introducted in the introduction, nor discussed in relation to the indentation model proposed here. This should be done.

I have the impression that the review of geologic research is trying to be complete, even if not every study did really bring new results. Therefore, it is somewhat cumbersome to go through this section, and I would recommend to concentrate on the studies that did really advance knowledge about the Schio-Vicenza fault.

There are some problems with the models applied.

• The zipper model of Passchier and Platt (2016) is definitely a major advance to understand possible relations of faults. However, when applying such a model, it is necessary to show that the fault in question have been active at the same time. In the manuscript, there is no information on timing of the second fault (Gamonda fault) involved in the „zippering“. If it cannot be shown that the involved faults moved contemporaneusly, an interpretation of truncation of an on older by a younger fault seems to be more probable.
• I do not know the Schio-Vicenza- and Gamonda fault personally, but in my experience it is a common observation to see contradicting observations of shear sense on brittle faults. Any brittle fault is a discontinuity, and will be reactivated during its younger history; especially if the orientation of the fault is sub-parallel to the stress field, minor changes in the orientation of the regional stress can produce fault reactivation wit opposite sense of shear. Usually, observation of offset of larger geological features is more reliable.
• Unfortunately, I do not understand the „30° transtensional model“. I have no idea what it is about – this must either be explained in a much clearer way, or omitted (see also annotations in the manuscript).

Not all figures are well suited to illustrate the content of the manuscript:

I miss a true tectonic map of the eastern Southern Alps and the adjacent forelands that illustrate the faults discussed in the text and show at least some units like the „plain region“ and the „chain sector“, which have not been defined in the manuscript. I suspect that these expressions refer to the foreland of the Venetian plain, and the Southern Alps thrust belt, respectively. It would also help if such a figure would include the Adamello pluton, and the Athesian and Trento platforms, and other names used is the manuscript, and which are not explained otherwise.

The present Figure 1 needs to be enlarged, and it would be nice to use color. Grey symbols on a grey background are not easy to read. Use a thicker stroke for the faults. Looking at the GPS velocity field, I ask myself, why there is neither a change of direction nor a change in velocity across the Schio-Vicenza fault system, if this is an active fault. This should be discussed in the text.

Hugo Ortner

References

Ratschbacher, L., Frisch, W., Linzer, G., Merle, O., 1991. Lateral extrusion in the Eastern Alps, Part 2: Structural analysis, Tectonics, pp. 257 - 271.

Reiter, F., Freudenthaler, C., Hausmann, H., Ortner, H., Lenhardt, W., Brandner, R., 2018. Active seismotectonic deformation in front of the Dolomites indenter, Eastern Alps. Tectonics 37, 4625-4654.

Rosenberg, C.L., Brun, J.-B., Gapais, D., 2004. Indentation model of the Eastern Alps and the origin of the Tauern Window. Geology 32, 997-1000.

Rosenberg, C.L., Brun, J.-P., Cagnard, F., Gapais, D., 2007. Oblique indentation in the Eastern Alps: Insights from laboratory experiments. Tectonics 26, TC2003.