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.
- Preprint
(6994 KB) - Metadata XML
-
Supplement
(41862 KB) - BibTeX
- EndNote
Status: final response (author comments only)
-
RC1: 'Comment on egusphere-2026-2658', Anonymous Referee #1, 30 Jun 2026
-
AC1: 'Reply on RC1', Giulia Patricelli, 28 Sep 2026
R1: lines refer to the original manuscript
Authors: lines refer to the updated version of the manuscript
Abstract
Line 20: “we dug some paleoseismological trenches”. Consider specifying the number of trenches or using a less vague expression than “some”.
Replaced “some” with “four”.
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.
Replaced with “insights” and modified the 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.
We moved Fig. 1 to the Introduction paragraph and included reference to Fig.1 at the beginning of the Introduction paragraph.
Lines 34–35: Use the abbreviation ESA since it has already been defined. Also check comma placement.
OK
Line 40: The word “some” seems unnecessary in this sentence and can likely be removed.
ok
Line 48: Again, the full expression for ESA is used despite previous definition. Please use abbreviations consistently throughout the manuscript.
OK
Line 50: Please define the abbreviation ELF.
We modified the sentence to: “on the bases of the reflection seismic lines acquired by ELF Aquitaine and…”
Line 51: Should "piedmont" be capitalized?
It should not be capitalized, as it is a geomorphological adjective.
Line 56: The wording “seismogenetic attention” is unclear. Please rephrase.
Modified with: “Barba et al. (2013) and Anderlini et al. (2020) focused on the Bassano Valdobbiadene Thrust, reporting for this tectonic structure a seismogenic potential greater than the Montello one”
Line 60: Again, avoid the vague term “some” and specify the number of trenches.
Replaced with “four”
Lines 66–67: Please use the abbreviation VVV, which was already defined. Apply the same correction throughout the manuscript.
OK
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.
Modified as follows (lines 63-64): “Our data provide important information that enables to strongly improve the seismic hazard assessment of this sector of the Southalpine region”
Seismotectonic setting
Line 111: Spell out "Last Glacial Maximum" and define LGM here, since this is the first occurrence.
ok
Line 126: Replace “for creeping” with “by creeping”.
Ok, done.
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.”
Ok, we modified the sentence as suggested.
Line 166: The word “gently” does not appear appropriate in this context.
We replaced with “provided by”.
Lines 167–174: Please report the electrode spacing and approximate depth of investigation of the ERT surveys.
Done
Line 177: Remove “some”.
OK
Line 182: Please specify the dated material (charcoal, plant remains, bulk sediment, etc.).
We added “of charcoal and bulk sediment”
Quaternary evolution of the study area
Line 200: Use only the abbreviation LGM after it has been defined.
ok
Line 212: Consider rephrasing. For example, replace “we can remember” with “it is worth noting”.
Ok, modified the sentence as follows (lines 216-217): “A remarkable example is the colossal Fadalto landslide, which occurred approximately 15 ka ago (Pellegrini and Surian, 1996)”.
Line 213: The term "over-deepened basins" may be more appropriate.
Ok, replaced the term.
Morphotectonic hints of recent tectonic activity of the Valdobbiadene-Vittorio Veneto Thrust
Line 217: Replace "hints" with a more precise term, such as "indicators".
OK, done.
Lines 219–220: The DEM analysis has already been described in the Methods section and does not need repetition.
We summarized the sentence as follows (lines 254-255): “The morphological anomalies identified through DEM analysis and potentially related to tectonic activity were subsequently validated by field survey”.
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.
We modified the wording, replacing with “incised riverbeds” as the features are classified on the map of Fig. 3.
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.
We added a sentence in the methodology paragraph explaining why we preferred sites with Holocene deposits for trenching (lines 160-164): “Because one of the main objectives of this study was to identify the most recent surface-faulting event for seismic microzonation purposes, trench sites were preferentially selected on Holocene deposits. These deposits provide sufficient stratigraphic resolution to distinguish individual paleoearthquakes, whereas the coarse-grained LGM gravels mainly preserve cumulative deformation, hampering the discrimination of successive faulting events.”
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?
As this is a Holocene distal alluvial-fan deposit incised into the LGM terrace, the interpretation in terms of depositional bars is difficult to support. It is more reasonable to interpret the upstream dip of the gravels as being related to tectonic tilting. We agree that the term “innermost” may be misleading and could be replaced with “distal.” We have therefore modified the sentence as follows (lines 247-248):
“In the distal portion of the Holocene alluvial fan, incised within the LGM fan, gravels are…”
Lines 247–248: Please briefly describe the geophysical anomaly.
We added this sentence to describe the geophysical anomaly (lines 253-254): “that shows an abrupt lateral contact between a low resistivity body uphill and a medium resistivity body downhill”.
We also add a file in the supplementary material (S1) collecting high-resolution images of ERT.
Line 278: Replace “across” with “cross”.
ok
Line 313: Correlated to which coseismic event? Or did you mean “related”?
Yes, “related”.
Line 338: Correct FO1 to F1.
ok
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.
The scarp may not be entirely tectonic. In addition to considering the possible role of fluvial erosion, we already hypothesize that, at the trench site, the scarp has been modified by human intervention (e.g., terracing and road construction). Therefore, the measured elevation difference should not be considered entirely tectonic in origin.
We added a part of the text explaining this aspect (lines 409-411): “Considering deformation, the morphological scarp associated with the fault trace (Fig. 12) is greater than the cumulative displacement documented in the trench, suggesting that post-seismic geomorphic evolution and/or anthropogenic modification may have contributed to its current morphology.”
Line 361: By “sharp gravels”, do you mean angular gravels?
Yes.
Line 416: Please briefly describe the ERT anomaly.
We added this sentence to describe the geophysical anomaly (lines 430-431): “…showing the abrupt contact between a medium resistivity body separating two portions of the surficial low resistivity body”.
Line 426: Replace "sedimented" with "deposited".
ok
Lines 429–430: As in previous trench descriptions, a photograph highlighting the fault plane would be beneficial.
We added a Fig. 20 showing a detail of the fault plane.
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.
As suggested by both the reviewers we have removed this part of the text from the Discussion.
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.
We added a sentence in the text to evaluate this hypothesis (lines 483-485): “The possibility that F2 and M2 represent two distinct events cannot be excluded; however, the available data are currently insufficient to support this interpretation”.
Line 494: Can uncertainty estimates be provided for ADs and ADt?
The ADs and ADt values reported in the manuscript represent the mean values of the displacements measured at the two sites. Specifically, ADt = 0.27 is the mean of the values measured at Cison1 (0.21) and Follina1 (0.32), whereas ADs = 0.49 is the mean of 0.29 and 0.69. We included the uncertainty range in parentheses both in the text and in table 5.
Regarding the magnitude values, although the uncertainty becomes apparent at the second decimal place, we consider the first decimal place sufficient for magnitude estimates derived from empirical relationships, given that the available information does not support a reliable estimate to the second decimal place.
Line 509: I did not receive Supplementary Material S5 for review. Please check that it has been included.
Thank you for pointing this out. There is no Supplementary Material 5 in the current version of the manuscript. The reference was left in the text from a previous version and has now been removed.
Line 528: Please explain the concept of “lost earthquakes” for readers unfamiliar with the term.
We added part of the text explaining the concept of lost earthquakes (lines 537-544): The concept of “lost earthquakes” (Stucchi et al., 2004) highlights the difficulties related to the reconstruction of historical seismicity and to the assessment of earthquake catalogue completeness. The absence of a historical earthquake from documentary records does not necessarily imply that the event did not occur, but may instead result from gaps in the production, preservation, or interpretation of historical sources. Therefore, catalogue completeness cannot be assessed solely through statistical approaches, but requires a critical evaluation of the historical and archival context in which seismic information was generated and transmitted. This issue is particularly relevant for poorly documented regions and for tectonic structures lacking clear historical seismicity, where apparent periods of seismic quiescence may partly reflect documentary gaps rather than the absence of past earthquakes.”
We also added some details in the conclusions paragraph (see next comment).
Conclusions
Line 552: Consider rephrasing the final sentence to more clearly explain the meaning of “lost earthquakes”.
We modified the sentence as follows (lines 566-568): “…numerous “lost” earthquakes affecting the Italian seismic record prior to the 15th century, whose absence from historical catalogues may reflect gaps in documentary evidence rather than the absence of seismic activity”.
Figures
Figure 1: Mark the location of Fig. 2.
ok
Figure 2: Indicate stream flow directions and the location of Fig. 3.
Done
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.
Ok, done.
Figure 9: The caption refers to blue squares and red triangles representing plastics and bricks, but these symbols are not visible.
The updated Fig.9 includes samples, bricks and plastic.
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.
The samples were recalibrated using the online version of OxCal and the IntCal20 calibration curve to ensure consistency across the dataset. We have therefore added a section to the Methods describing the calibration procedure in detail (lines 178-181): “To ensure consistency across the dataset, radiocarbon ages originally calibrated by Beta Analytic using IntCal13 were recalibrated based on the original conventional radiocarbon ages using IntCal20 in the online version of OxCal v4.4 (Bronk Ramsey, 2021)”.
Tables and captions were updated accordingly.
Table 5: Please provide uncertainty estimates for ADt, ADs, and the corresponding Mw values.
See previous comment on uncertainty values of ADt, Ads and corresponding Mw values.
-
AC1: 'Reply on RC1', Giulia Patricelli, 28 Sep 2026
-
RC2: 'Comment on egusphere-2026-2658', Christoph Grützner, 02 Jul 2026
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
-
AC2: 'Reply on RC2', Giulia Patricelli, 28 Sep 2026
R2: lines refer to the original manuscript
Authors: Lines refer to the updated version of the manuscript
Title
Perhaps simplify the title to: "Historical tectonic activity along the Bassano-Valdobbiadene Thrust
(eastern Southern Alps, Italy)"
no seismic hazard assessment is done in this paper
We modified the title: “Paleoseismological evidence constraining the Historical tectonic activity of the eastern segment of the Bassano-Valdobbiadene Thrust (eastern Southern Alps, NE Italy)
Abstract
please try to use fewer place names in the abstract, it's a bit complicated to read with the large number of geographic terms
We have simplified the Abstract by removing the names of minor localities and retaining only those considered necessary.
Line 21: linear morphogenic, replace with surface-rupturing
Done.
Introduction
Line 28 “the assessment of the seismic hazard in a region”. This is absolutely not wrong, but your paper is not about seismic hazard in the first place. You do not discuss the implications of your results for the regional seismic hazard anywhere. So perhaps start the introduction differently in order to not lead the reader to false expectations.
We modified the text as follows “The seismotectonic characterization of low deformation rates regions, such as the eastern Southern Alps….”
Fig.1
Add localities
INSET: I think that all the text in this inset map is too small to be legible, and that without further details or annotations, it doesn't tell a lot about the regional tectonics.
Perhaps show general morphology with some simplified motion arrows and plate convergence rates. Or morphology plus Adria-Europe plate boundary. Or Enrico Serpelloni's rate maps.
- please add info on coordinate system/EPSG in the caption; I guess it's some UTM zone 32N or 33N?
-Please add a legend for the size of the stars (mag of the earthquakes), or add mag in the labels
-1268 event is discussed in the text but not plotted here
We updated Fig. 1 following the comments:
We added the localities and the mountains cited in the paragraph.
We have modified the figure inset by replacing it with a figure from Devoti et al. (2011).
Done
Done
We also inserted in this Figure the earthquakes cited in the text from Guidoboni et al. (2019). The different symbol used for these events is indicated in the legend of the updated Figure1.
Line 58. In this paper
This entire section is very similar to the abstract. I would try to avoid that.
We modified this part of the text as follows (lines 55-62): “In this paper, we investigate the recent activity of the Valdobbiadene–Vittorio Veneto segment (hereafter VVV), which represents the eastern sector of the Bassano–Valdobbiadene Thrust Auct. (Castellarin, 1981; Antonelli et al., 1990) and extends along the foothills between Miane and Cison di Valmarino localities (Fig. 2). In this area, Earthquake Catalogues (Locati et al., 2022; Rovida et al., 2021; Guidoboni 2018, 2019) do not report any strong seismic event during the last millennium. Morphotectonic and geophysical investigations carried out within the Seismic Microzonation Project (Gruppo di Lavoro MS, 2008) identified features possibly associated with the surficial trace of the VVV segment. Based on the preliminary results, the paleoseismological investigation conducted across the inferred surficial trace of VVV allowed us to constrain its Holocene/historical tectonic activity, and to evaluate its capability (sensu Gruppo di Lavoro MS, 2008; Linee Guida MS, 2015)”.
Line 63
Ins. ref to Fig.2 when citing Miane e Cison di Valmarino
We modified the text avoiding minor localities.
Line 67. Linear
What does linear mean in this context?
We replaced with “surface rupturing earthquakes”
Seismotectonic setting
Line 72 Pliocene-Quaternary front:
not sure what this refers to - to the rocks? to the activity? Later in the same sentence we learn that the fold-and-thrust-belt was active since middle Miocene...?
Our intention was to refer to the youngest (Pliocene–Quaternary) frontal sector of the polyphase Southern Alps fold-and-thrust belt, whose tectonic evolution began in the middle Miocene. We have revised the sentence to clarify this distinction (lines 76-77): “The study area belongs to the Pliocene–Quaternary tectonic front of the eastern Southern Alps, which represents the youngest frontal sector of a polyphase S–SE–verging, WSW–ENE striking fold and thrust belt active since middle Miocene (Fig. 1)”
Line 87 Silent.
In the sense that they probably creep or slip aseismically, or in the sense that we simply didn't observe an earthquake because their average recurrence interval is thousands of years?
Our use of the term "silent" was intended to indicate the lack of documented strong historical earthquakes, not aseismic slip or creep. We have replaced the term silent with a clearer expression specifying that these sources have no record of strong historical earthquakes during the historical period (lines 84-86): “Conversely, the same data indicate that some of the main potential seismogenetic sources of the ESA front (DISS Working Group, 2025) did not have strong earthquakes and therefore appear inactive in the available historical record.”
Lines 89-90: the Schio–Vicenza Fault–System (Zampieri et al., 2021) and the Arba–Ragogna Thrust–System (Galadini et al., 2005; Zanferrari et al., 2008; Poli et al., 2009; Poli et al., 2024).
but the same is true for the BV1, the AC, the MT-CN, and the PZ (at least) according to Fig. 1
- cite Poli as (...; Poli et al., 2009, 2024)
The seismicity associated with the other tectonic structures is discussed later in the manuscript. In particular, the seismicity of the AC and MT-CN systems is discussed in the context of the studies that have attributed earthquakes with M > 5 to these structures (lines 116–124). For BV1, we state that no earthquakes have been associated with this structure (lines 88-89). We didn’t mention PZ because it is far from the study area, but the deep ramp of PZ is associated with the September 1976 earthquake (Galadini et al., 2005).
Line 122. Earthquakes from Guidoboni
Missing on the map because they are <M5.5 (1268 and 1859) or older than 1000 years (778). Since you discuss them here, perhaps add them anyway to Fig. 1?
We included the earthquakes from Guidoboni cited in the manuscript in Fig. 1 with a different symbol (green stars), as indicated in the legend.
Method
Lines 168-172
I think this can probably be deleted, because it's general description only
ok
Lines 173-175: inverted to obtain 2D resistivity sections
Which software did you use?
The software used is ZondRes2D as indicated in line 172.
Fig. 2
Modificare Unit in units
Correggere heRmipelagic
Caption: Regarding the citation, you cite sheet 22, but not 38, 37, 23. Please use a consistent citation style if possible.
Done
Done
We cited sheets 38, 37 and 23 with the same style of Sheet 22, but they belong to different cartographies.
Sheets 38, 37 and 23 belong to the Carta Geologica delle Tre Venezie, while Sheet 22 belong to the Carta Geologica d’Italia. To help the reader, we modified the reference in the caption.
4 Quaternary evolution of the study area
Lines 212-213 rephrase
We rephrased as follows: “The lack of vegetation cover on the slopes, together with intense surface runoff, favoured the mobilisation of large amounts of landslide material and debris into the valleys. A remarkable example is the colossal Fadalto landslide, which occurred approximately 15 ka ago (Pellegrini and Surian, 1996).”
4.1 Morphotectonic hints of recent tectonic activity of the Valdobbiadene-Vittorio Veneto Thrust
Fig. 3
At 100% zoom level it's very hard to differentiate the symbols; can you make the ticks larger?
In the legend Landslide maiuscolo
We updated Fig.3 making the symbols larger.
Fig. 4 and all detail maps
Add Ohm*m in the ERT color bar
Check captions
All detail maps (Figs. 4, 8, 11 and 17) were updated adding the Ohm*m in the ERT colorscale.
Line 243: suggesting a Holocene tilting
it sounds like the tilt implies a Holocene age, but it's the position of the gravels (and the fact that they are unconsolidated?)
As this is a Holocene distal alluvial-fan deposit incised into the LGM terrace, the interpretation in terms of depositional bars is difficult to support. It is more reasonable to interpret the upstream dip of the gravels as being related to tectonic tilting. We agree that the term “innermost” may be misleading and could be replaced with “distal.” We have therefore modified the sentence as follows (lines 247-248):
“In the distal portion of the Holocene alluvial fan, incised within the LGM fan, gravels are…”
Fig. 5
please add a second panel below in which the image is 50% transparent and you draw the interpretation on it
We modified Fig.5 adding a light interpretation on the original photo.
5.1 Cison 1 trench (Case dalla Libera locality)
Line 260: Unit F
What about units G and H?
We added this sentence (lines 267-268): “In the southernmost portion of the wall, an alluvial fan deposit composed of gravel with cobbles in a sandy-silty matrix overlies unit F. Unit G, the uppermost unit, consists of ploughed soil.”
Lines 269-270 Reimer et al 2013 e 2020
Why using two different calibration curves?
The samples were recalibrated using the online version of OxCal and the IntCal20 calibration curve to ensure consistency across the dataset. We have therefore added a section to the Methods describing the calibration procedure in detail (lines 178-181): “IntCal13 or IntCal20 atmospheric calibration curves (Reimer et al., 2013, 2020). To ensure consistency across the dataset, radiocarbon ages originally calibrated by Beta Analytic using IntCal13 were recalibrated based on the original conventional radiocarbon ages using IntCal20 in the online version of OxCal v4.4 (Bronk Ramsey, 2021)”.
Tables and captions were updated accordingly.
5.2 Follina 1 Trench (alla Sega locality)
Fig. 8
In legend Morpho
Add Ohmm
Caption
done
Fig. 9
Samples in the log are missing
The updated Fig.9 includes samples, bricks and plastic.
Line 304
to 1666-1783 cal CE for the shallowest deposits
But Unit H contains plastic, so it must be 17th century to modern.
What about Unit G?
We extended the age interval referred to unit H (17th and 21th centuries) and we added a sentence to explain our interpretation (lines 319-323): “…the subsequent anthropogenic infill deposited between the 17th and 21st centuries. Since no medium-to-strong earthquakes have been reported in the Italian seismic catalogues for the study area since the 17th century, it is reasonable to infer that the identified event occurred shortly after the 17th century. This vertical displacement can be related to a coseismic event”.
We have moved the description of Unit G to the earlier section of the text where the other units are described (line298).
Line 310: middle-angle
Please provide precise numbers or a range of dips
We added the 30° dip mesaure.
Fig. 10:
c: please also label units A and B
Fig. 10 has been updated with labels A and B.
Line 319: sandy body (unit G)
move the unit description up to the paragraph with the other unit descriptions
Done, see previous comment.
Line 320: could be referred to liquefaction
rather explain what speaks in favour of liquefied material - do you see any typical sedimentological features like flame structures etc?
We added a sentence to support our interpretation (lines 329-331): “This interpretation is supported by its subvertical geometry, which crosscuts the entire stratigraphic succession down to the base of Unit H and is difficult to reconcile with natural depositional processes”.
Line 323 presence of local perched aquifers is documented:
How?
We add the detail of the depth of perched aquifers and the associated reference (lines 332-333).
Line 328: probably referred to liquefaction event:
This is a tricky part of the trench indeed. This paper reports imbricated gravels due to liquefaction, too: https://www.sciencedirect.com/science/article/pii/S0037073800000695
Takahama et al., 2000
You might want to cite it here or in the discussion to support your arguments
We thank the Reviewer for this helpful suggestion, which prompted us to expand the relevant bibliography. However, we believe that our original interpretation, assessing for the tectonic nature of the sc structures in the southern portion of the wall, is still the most appropriate.
5.3 Miane 3 Trench (via Giorgione)
Line 343-344: morphological scarp:
Is it a fault scarp? OK, it's parallel to the fault trend, but it is also parallel to the river, to the slope, and to the man-made terraces.
The scarp may not be entirely tectonic. In addition to considering the possible role of fluvial erosion, we already hypothesize that, at the trench site, the scarp has been modified by human intervention (e.g., terracing and road construction). Therefore, the measured elevation difference should not be considered entirely tectonic in origin.
We added a part of the text explaining this aspect (lines 408-410): “Considering deformation, the morphological scarp associated with the fault trace (Fig. 12) is greater than the cumulative displacement documented in the trench, suggesting that post-seismic geomorphic evolution and/or anthropogenic modification may have contributed to its current morphology.”
Line 382: scarp coincides with:
yes, but the faulting can not explain the scarp height and unit C is also not folded, so the scarp is somewhat mysterious to me - what is your idea on scarp formation?
Lines 384-396:
yes, I see that, but it's probably enough to have few centimeters if shortening to create this bulge - could have happened in the same event as the faulting
We have also clarified the folding deformation by distinguishing the deformation associated with the shear plane beneath the morphological scarp from the broad fold observed in the southernmost part of the trench, which we interpret as being related to a deep frontal splay (lines 403-414)
Lines 388-389: agree for an articulated deformation and seismic history of the fault plane:
please rephrase, I don't understand what is meant
We rephrased as follows (lines 395-397):
“In this regard, we detected at least two distinct coseismic events on the fault plane. In order to reconstructed the seismic history of the tectonic structure, we restored the trench wall log and successively we validated the restoration through the forward model construction in 3D Move (Fig. 16)”.
Line 398: standard value of about 15° for the original dip slope:
Please explain - why 15°? What is this the standard value for? Is this the average dip of the unit B between 10 - 35 m?
Line398: folding deformation
between 0 and 5 m in the trench, unit A and P dip steeper than the overlying units - is this why you infer folding? If so, please explicitly state it.
Line 400: upwarping in the southern portion of the wall should also be considered
can you extract any meaningful data from the warping? Like the shortening that would be required to create the bulge?
Line 408: folding deformation affecting the entire stratigraphic succession.
All this description of folding is a bit vague. Is unit C folded or not? If not (and that is what it looks like to me), the event must be older.
Is D2 really folded and not just draped onto a pre-existing scarp?
Line 411: recent times (M1)
well, the gentle warping between 10-25 m could have happened in the same event as the offset of unit P, A, and B, right?
FIG.16:
D2 is pretty steep for a depositional unit... and actually, so is D1.
It is not clear to me how the scarp formed.
We modified the sentence as follows (lines 404-407): “Moreover, the dip slope of about 15° measured on the southern portion of the wall is compatible with the deposition of distal alluvial fan, while, at the hangingwall of the fault plane, unit A and P dip steeper than 15°, therefore we infer the presence of a buried reverse splay at the footwall of the main fault (between sections -1 and -3, Fig. 13) which caused the folding.”
We also modified the text trying to better explain our interpretation of the folding deformation: we attribute the folding of the northern portion of the trench wall (units P, A and B – sections -1 to -3) to a buried secondary splay (lines 405-407).
An additional reverse buried plane must be present in the southern portion of the trench wall (sections -35 to -19) which caused the folding of the entire sequence up to the topographic surface (lines 412-415).
We also added the hypothesized buried reverse planes in the wall interpretation (Fig. 13 and in the supplementary material S4).
5.4 Miane 1 Trench (Vergoman locality)
Line 425 Units A, B and C:
Please describe them at least briefly. This is important because you use them as markers. So the reader needs to be able to judge if it's really unit C that sits next to the fault plane, because from the high-res orthophoto in the supplement it is not easy to see
Ok, we added a detailed description of the units (lines 441-442): “The Miane 1 trench investigated a series of local colluvial deposits (Units A, B, C), characterized by an average south dipping stratification (Fig. 19): the slightly silty clay with 30% gravel and cobbles (unit A), the gravel with silt and clay (unit B) and gravel with a silty-clayey matrix (unit C, clasts/matrix ratio =70-30%), alternating with silty clay lenses (unit C1)”.
Line 430: 30 cm minimum displacement
how did you measure it? I assume by the thickness of unit C? In the orthomosaic, I can't see the difference between A and C.
There is also this coarse layer within unit A that you marked with a dashed line on either side of the fault - does this record 30 cm of slip? It's hard to see, it could also bend. I guess the gravels stop before reaching the fault zone.
Please add a zoom-in photograph of the fault zone to convince the reader the fault is actually there. The faults in the other three trenches are presented in a more convincing way
We thank the reviewer for this comment since it helped us to revise the vertical displacement measured in trench site Miane1.
The dashed lines within unit A indicate the orientation of the identified layers and do not necessarily represent the same layer, as the layer is not continuous.
Regarding the throw, since unit C is not present at the hangingwall of the fault, we measured the vertical slip on the top of unit A, thus estimating a cumulative minimum throw pre unit C. We know that the fault further activated after the deposition of unit C, but we are not able to estimate the amount of slip post unit C, therefore we did not include trench site Miane 1 for the reconstruction of the events (updated Fig. 21).
We updated both the text (lines 448-452 and lines 491-495) and the figures accordingly.
We add Fig.20 showing a detail of the fault plane, as for the other trenches.
Line 437 evidence of deformation:
please describe it, not just mention it - it is not super-convincing in my view
See previous comment.
6 Discussion
Lines 441-458: consider removing this entire section
We did, we removed this part of the text.
6.1 Source parameters (last event of activation and displacement per event)
Line 461 historical:
but you also have older deposits...?
We modified the sentence as follows (lines466-467): “…deforming and displacing Holocene deposits, including those of historical age, up to the ground surface”.
Lines 463-465
I would delete this paragraph, it's very confusing. Below you provide details on all deformation events, so better not confuse the reader by mentioning oldest and youngest deformed deposits over all trenches here.
Ok, we removed this part of the text as suggested by both the reviewers.
Line 467: main seismic events: E1 and E2
Why are E1 and E3 main events, and E2 is apparently minor?
We have modified the text by listing the three events from the outset. Each event is then described with detail (lines 468-487).
Lines 472-473:
I think the age of this warping is poorly constrained, and I am not 100% sure it needs to be tectonic..
See previous comments.
Line 477:
I don't understand why you not simply work systematically through all three events E1 to E3. This confuses me.
We modified the text (see previous comment).
Line 479: manufact
artifact?
Replaced with “cobble-paved road”
Line 484-485:
But in Fig. 20 you indicate that the 30 cm of throw date to 2000 BCE?
The updated throw value of 20 cm is referred to the minimum displacement cumulated up to the deposition of unit C (post B and pre C).
Line 491:
AD, ADs, ADt... too many abbreviations = confusing
We removed some acronyms from the main text.
6.2 Possible historical earthquake
Line 528: lost earthquakes
please explain to the reader who are not familiar with Galli's paper
We added part of the text explaining the concept of lost earthquakes (lines 537-544): The concept of “lost earthquakes” (Stucchi et al., 2004) highlights the difficulties related to the reconstruction of historical seismicity and to the assessment of earthquake catalogue completeness. The absence of a historical earthquake from documentary records does not necessarily imply that the event did not occur, but may instead result from gaps in the production, preservation, or interpretation of historical sources. Therefore, catalogue completeness cannot be assessed solely through statistical approaches, but requires a critical evaluation of the historical and archival context in which seismic information was generated and transmitted. This issue is particularly relevant for poorly documented regions and for tectonic structures lacking clear historical seismicity, where apparent periods of seismic quiescence may partly reflect documentary gaps rather than the absence of past earthquakes.”
We also modified the sentence in the Conclusions paragraph as follows (lines 566-568): “…numerous “lost” earthquakes affecting the Italian seismic record prior to the 15th century, whose absence from historical catalogues may reflect gaps in documentary evidence rather than the absence of seismic activity”.
FIG. 21: mark the study area
Done, now Fig.22
DISCUSSION
What's missing from the discussion in a critical view on the warping and the nature of the scarp at site Miane3. I am not 100% convinced it is tectonic deformation that we see there. Also, all ages are taken as correct, but this is certainly not the case. Charcoal 14C ages (or charred material) is not necessarily close to the depositional age. Often yes, but not always - the charcoals may have been somewhere uphill in the landscape for an unknown amount of time. This can perhaps be neglected and there's not much we can do about it, but it should at least be mentioned somewhere.
Bulk organic material is often problematic. There are examples from paleoseismological studies where such ages are highly variable within one layer, that is, thousands of years apart. Again, not much can be done about that, but a note of caution would be good. The organic material that is actually dated in bulk samples could be pedogenic carbonate, recycled rock carbonate, plant remains, a mixture of all of that - who knows.
We have added additional explanations at several points throughout the manuscript to clarify the aspects related to:
- the nature of the scarp and warping of Miane 3 site (see paragraph Miane 3 Trench paragraph);
- uncertainty of the C14 dating (see Methods paragraph)
Conclusions
Line 536 linear
I don’t know what it means here
Replaced with: “surface rupturing”.
Viewed
| HTML | XML | Total | Supplement | BibTeX | EndNote | |
|---|---|---|---|---|---|---|
| 218 | 103 | 38 | 359 | 39 | 17 | 22 |
- HTML: 218
- PDF: 103
- XML: 38
- Total: 359
- Supplement: 39
- BibTeX: 17
- EndNote: 22
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1
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.