the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 10 Jun 2026
Historical tectonic activity along the eastern segment of the Bassano-Valdobbiadene Thrust: new hints for the seismic hazard assessment of the Venetian Prealps between Vittorio Veneto and Valdobbiadene (eastern Southern Alps, NE Italy)
Abstract. In the framework of the Italian Seismic Microzonation Project, we investigated the easternmost segment of the Bassano–Valdobbiadene Thrust Auct. (i.e. the Vittorio Veneto–Valdobbiadene Thrust) which runs at the base of the Venetian prealpine foothill between Miane, Follina and Cison di Valmarino municipalities (NE Italy). The Bassano–Valdobbiadene Thrust belongs to the SW–NE striking, SE–verging Pliocene–Quaternary front of the eastern Southern Alps which at present, accommodates deformation with velocities of the order of 2–3 mm/yr. Prominent geological and morphological expression (Mt. Grappa–Mt. Cesen–Mt. Visentin anticlines) underlies the Miocene to Present tectonic activity of the Bassano–Valdobbiadene Thrust, however the Quaternary tectonic activity is scarcely constrained. The historical seismicity reveals that few destructive earthquakes (M≥5.5) hit the Venetian prealpine region, but no significant seismic events affected Follina and the surrounding areas during the last millennium. In order to investigate the recent tectonic activity of this sector of the eastern Southalpine front, we made a morphotectonic survey along the San Pietro and Soligo valleys (i.e. the Vallata valley) and, in correspondence of possible morphotectonic evidence, a series of Electroresistivity Tomography investigations. Following, we dug some paleoseismological trenches across the possible surficial trace of the tectonic structure. The results of our study pinpointed that the Vittorio Veneto–Valdobbiadene Th. is an active fault, capable to generate linear morphogenic earthquakes. Particularly, the paleoseismological analysis highlighted that the last seismic event referable to the investigated structure occurred during the High–Middle Age (13th–14th century CE). The event produced a maximum observed displacement of 32 cm, while magnitude estimates suggest an earthquake of Mw 6.5–6.7. These data provide new important seismotectonic hints, which have to be considered in order to re–evaluate the seismic hazard of the Venetian Prealpine region, characterized by high population and industrial density.
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Status: open (until 22 Jul 2026)
- RC1: 'Comment on egusphere-2026-2658', Anonymous Referee #1, 30 Jun 2026 reply
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RC2: 'Comment on egusphere-2026-2658', Christoph Grützner, 02 Jul 2026
reply
Review Poli et al. – “Historical tectonic activity along the eastern segment of the Bassano-Valdobbiadene Thrust: new hints for the seismic hazard assessment of the Venetian Prealps between Vittorio Veneto and Valdobbiadene (eastern Southern Alps, NE Italy)”
The paper is about paleoseismological investigations along the Alpine front in northeastern Italy. Before trenching, the authors conducted very detailed morphological mapping with the help of high-resolution digital elevation data, and they used geoelectrical surveys to identify promising trench sites. In this area, little was known about the earthquake history of the capable faults besides the historical and instrumental seismicity. The authors managed to date the last three surface-breaking seismic events and, thus, filled that knowledge gap. That’s a great achievement because the area is notoriously hard for this kind of studies and the data are urgently needed to better understand the regional tectonics. The data are also useful for future seismic hazard calculations. The manuscript is not novel from a methodological point of view, but this is not a downside in this case.
In general, the paper is in a good shape and I am looking forward to seeing the data published. There are a few issues that need to be addressed, which is why I suggest asking for revisions.
- Does the paper address relevant scientific questions within the scope of SE?
Yes. The topic of the study lies within the scope of SE. Potential readers are (tectonic) geomorphologists, earthquake geologists, paleoseismologists, the seismic hazard community of Italy, Slovenia, and Austria, regional and national authorities and agencies, people working on the geology of N Italy. The scientific question is relevant.
- Does the paper present novel concepts, ideas, tools, or data?
The paper is about very relevant new data that were collected with established approaches.
- Are substantial conclusions reached?
Yes, the study managed to extract the information they were aiming for. The data are new and fill a regional knowledge gap.
- Are the scientific methods and assumptions valid and clearly outlined?
Yes, although I think the radiocarbon dating of bulk organic material comes with uncertainties so high that these should be explicitly stated and discussed.
- Are the results sufficient to support the interpretations and conclusions?
Yes, in most cases. I have never seen a paleoseismological trench that did not give rise to controversial opinions, and it’s the same here. A few of the author’s interpretations could perhaps be more conservative, or at least a non-tectonic interpretation could be critically discussed even if the authors stick to their interpretation. This concerns for example the scarp at site Miane 3 and the amount of displacement that can be inferred from trench Miane 1.
- Is the description of experiments and calculations sufficiently complete and precise to allow their reproduction by fellow scientists (traceability of results)?
Yes, in most cases. The high-res trench orthophotos in the supplement are good, but they are not high-res enough to see everything that was described in the text. In a few places I would have wished for a more detailed description of the units (and their offsets) in the trenches. This could perhaps be published in the supplement in order to not make the manuscript excessively long.
- Do the authors give proper credit to related work and clearly indicate their own new/original contribution?
Yes, absolutely.
- Does the title clearly reflect the contents of the paper?
The title could be improved. The paper is not about seismic hazard assessment, so I would omit that term. The title is also very long and, frankly, contains a lot of placenames not everyone is familiar with. The location name Valdobbiadene should perhaps not appear more than once in the title.
- Does the abstract provide a concise and complete summary?
Yes, but it also suffers a bit from a very large number of different place names that make it hard to read. I think that for example the names of individual streams are not necessary – the authors have a great story to tell, but they need to tell the big picture.
- Is the overall presentation well structured and clear?
Yes, the manuscript is well-organized and the presentation is clear. I would have expected a somewhat longer discussion.
- Is the language fluent and precise?
No, at present the language makes it a bit hard to read the manuscript. Sentences are often very long. Many different placenames, some of which are not on a map, interrupt the flow of the text. A lot of abbreviations are used. There are many vague descriptions like “some” or “strongly”. The text is rather wordy with phrases like “show a lack of” instead of “lack” or “from a … point of view”. All of this is not wrong, but it would improve the manuscript to make the language more precise.
- Are mathematical formulae, symbols, abbreviations, and units correctly defined and used?
Yes.
- Should any parts of the paper (text, formulae, figures, tables) be clarified, reduced, combined, or eliminated?
The text can be shortened a bit, but not the content.
- Are the number and quality of references appropriate?
Yes, but not all references cited in the text appear in the reference list and vice versa.
- Is the amount and quality of supplementary material appropriate?
No, one supplementary file seems to be missing (S5) and the trench orthophotos need a higher resolution if possible.
More specific comments can be found in the annotated PDF. I am happy to see these wonderful new data, and I am looking forward to seeing this paper published.
Christoph Grützner
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Review report
The manuscript entitled “Historical tectonic activity along the eastern segment of the Bassano-Valdobbiadene Thrust: new hints for the seismic hazard assessment of the Venetian Prealps between Vittorio Veneto and Valdobbiadene (eastern Southern Alps, NE Italy)” presents a morphotectonic, geophysical, and paleoseismological investigation of the eastern segment of the Bassano-Valdobbiadene Thrust in the Venetian Prealps, aiming to assess its paleoseismic activity and implications for seismic hazard. I find the topic important for both the regional seismotectonic community and seismic hazard practitioners, and therefore well within the scope of Solid Earth. The authors employ a comprehensive multidisciplinary approach, combining geomorphological analysis, geophysical investigations, and paleoseismological trenching, which represents the most appropriate methodology for investigating active faulting in slowly deforming regions. The study provides, for the first time, evidence for both historical and prehistoric surface-rupturing earthquakes along this sector of the thrust system and therefore constitutes a potentially significant contribution to the understanding of seismic sources in the eastern Southern Alps.
The manuscript is generally well written and supported by a substantial amount of graphical material that effectively illustrates the results and interpretations. In particular, the integration of ERT surveys with trench locations is very well presented and provides valuable support for the selection of excavation sites and the interpretation of subsurface structures. However, I strongly recommend providing the full-resolution ERT profiles in the Supplementary Material. The ERT data constitute an important component of the study, and making the complete profiles available would allow readers to independently evaluate the details of the geophysical interpretations while preserving the clarity of the figures in the main text.
The manuscript would benefit from several improvements before publication. While the overall scientific approach is sound, a number of issues related to terminology, consistency, clarity of presentation, and interpretation should be addressed. Throughout the manuscript, abbreviations are often defined but subsequently replaced by their full forms, resulting in inconsistencies that hinder readability. A more systematic use of abbreviations would improve the flow of the text. Several statements would also benefit from more precise wording, as expressions such as “some” or “hints” appear overly vague for a scientific manuscript. Some geomorphic interpretations would benefit from a more explicit discussion of alternative explanations. For example, the origin of certain scarps and tilted surfaces is interpreted primarily in a tectonic context, whereas possible fluvial or depositional origins are not always considered. Presenting and evaluating alternative hypotheses would strengthen the interpretations and increase confidence in the conclusions. The discussion section could also be improved by avoiding repetition of information already presented in the seismotectonic setting chapter and by providing uncertainty estimates where quantitative parameters are introduced.
Specific comments
Abstract
Line 20: “we dug some paleoseismological trenches”. Consider specifying the number of trenches or using a less vague expression than “some”.
Line 24: “These data provide new important seismotectonic hints, which have to be considered”. The term "hints" is not appropriate in this context. Please rephrase. I would also recommend avoiding the word "hints" in the manuscript title.
Introduction
General comment: The scientific problem is clearly introduced and supported by adequate references. However, it would be helpful to include a reference to Fig. 1 within the introduction to facilitate spatial orientation from the beginning.
Lines 34–35: Use the abbreviation ESA since it has already been defined. Also check comma placement.
Line 40: The word “some” seems unnecessary in this sentence and can likely be removed.
Line 48: Again, the full expression for ESA is used despite previous definition. Please use abbreviations consistently throughout the manuscript.
Line 50: Please define the abbreviation ELF.
Line 51: Should "piedmont" be capitalized?
Line 56: The wording “seismogenetic attention” is unclear. Please rephrase.
Line 60: Again, avoid the vague term “some” and specify the number of trenches.
Lines 66–67: Please use the abbreviation VVV, which was already defined. Apply the same correction throughout the manuscript.
Line 68: “Our data strongly improve the seismic hazard assessment.” The data themselves do not improve hazard assessment, but rather provide information that enables improved assessments. Please rephrase.
Seismotectonic setting
Line 111: Spell out "Last Glacial Maximum" and define LGM here, since this is the first occurrence.
Line 126: Replace “for creeping” with “by creeping”.
Methods
Line 163: “we used a multidisciplinary approach to realize the present seismotectonic study.” Please rephrase, for example: “we used a multidisciplinary approach for the seismotectonic investigation.”
Line 166: The word “gently” does not appear appropriate in this context.
Lines 167–174: Please report the electrode spacing and approximate depth of investigation of the ERT surveys.
Line 177: Remove “some”.
Line 182: Please specify the dated material (charcoal, plant remains, bulk sediment, etc.).
Quaternary evolution of the study area
Line 200: Use only the abbreviation LGM after it has been defined.
Line 212: Consider rephrasing. For example, replace “we can remember” with “it is worth noting”.
Line 213: The term "over-deepened basins" may be more appropriate.
Line 217: Replace "hints" with a more precise term, such as "indicators".
Lines 219–220: The DEM analysis has already been described in the Methods section and does not need repetition.
Lines 222–223: I do not clearly recognize the described pattern of water gaps in Fig. 3. Please clarify the wording or indicate the relevant features more clearly in the figure.
Paleoseismological trenching
General comment: From Fig. 3, I infer that trench sites were preferentially selected on Holocene surfaces while LGM surfaces were avoided. Out of scientific curiosity, could the authors explain this choice? LGM surfaces might preserve longer paleoseismic records and potentially more cumulative deformation.
Lines 243–244: The northward tilting is interesting. Could it have an origin other than tectonic deformation, for example depositional inclination of gravel bars in a braided river environment?
Lines 247–248: Please briefly describe the geophysical anomaly.
Line 278: Replace “across” with “cross”.
Line 313: Correlated to which coseismic event? Or did you mean “related”?
Line 338: Correct FO1 to F1.
Lines 343–345: Is the morphological scarp truly a fault scarp, as indicated in Fig. 11? Given its approximately 2 km length following the valley, a fluvial origin (e.g., terrace riser or erosional scarp) should also be considered. Furthermore, the 2 m scarp height appears difficult to reconcile with the roughly 20 cm displacement observed in the trench.
Line 361: By “sharp gravels”, do you mean angular gravels?
Line 416: Please briefly describe the ERT anomaly.
Line 426: Replace "sedimented" with "deposited".
Lines 429–430: As in previous trench descriptions, a photograph highlighting the fault plane would be beneficial.
Discussion
Lines 441–458: This information appears more appropriate for the Seismotectonic setting section. Much of it is already presented there. Consider moving or integrating this material.
Lines 482–483: It may be worth considering whether the event interpreted as E2 in both the Miane 3 and Follina 1 trenches could instead represent two distinct earthquake events.
Line 494: Can uncertainty estimates be provided for ADs and ADt?
Line 509: I did not receive Supplementary Material S5 for review. Please check that it has been included.
Line 528: Please explain the concept of “lost earthquakes” for readers unfamiliar with the term.
Conclusions
Line 552: Consider rephrasing the final sentence to more clearly explain the meaning of “lost earthquakes”.
Figures
Figure 1: Mark the location of Fig. 2.
Figure 2: Indicate stream flow directions and the location of Fig. 3.
Figure 3: Indicate stream flow directions. The legend appears to contain two symbols for LGM alluvial fan deposits. Please check whether one should represent a different unit. The fault-zone depiction using a transparent broad band is excellent and particularly effective for communicating fault-zone uncertainty and width. Mark the locations of Figs. 4, 8, 11, and 17.
Figure 9: The caption refers to blue squares and red triangles representing plastics and bricks, but these symbols are not visible.
Tables
Tables 1–4: Different calibration curves appear to have been used. For consistency and comparability, I recommend recalibrating all radiocarbon dates using the latest calibration curve and updating the manuscript accordingly.
Table 5: Please provide uncertainty estimates for ADt, ADs, and the corresponding Mw values.
Overall recommendation: minor revision
The study presents an important and novel dataset with clear relevance for active tectonics and seismic hazard assessment. The main conclusions are generally supported by the data, and I do not identify any major scientific flaws. Most of my comments concern clarification, consistency, additional methodological details, consideration of alternative interpretations, and improvements in presentation. Addressing these points will significantly strengthen the manuscript and enhance its value to the scientific community.