Geodynamic and seismotectonic model of a long-lived transverse structure: The Schio-Vicenza Fault System (NE Italy)

. We make a thorough review of geological and seismological data on the long-lived Schio-Vicenza Fault System (SVFS) in northern Italy and present for it a geodynamic and seismotectonic interpretation. The SVFS is a major and high angle structure transverse to the mean trend of the Eastern Southern Alps fold-and-thrust belt, and the knowledge of this structure is deeply rooted in the geological literature and spans for more than a century and a half. 10 The main fault of the SVFS is the Schio-Vicenza Fault (SVF), which has a significant imprint in the landscape across the Eastern Southern Alps and the Veneto-Friuli foreland. The SVF can be divided into a northern segment, extending into the chain north of Schio and mapped up to the Adige Valley, and a southern one, coinciding with the SVF proper. The latter segment borders to the east the Lessini, Berici Mts.Mountains and Euganei Hills block, separating this foreland structural high from the Veneto-Friuli foreland, and continues southeastward beneath the recent sediments of the plain via the blind Conselve- 15 Pomposa fault. The structures forming the SVFS have been active with different tectonic phases and different style of faulting at least since the Mesozoic, with a long-term dip-slip component of faulting well defined and, on the contrary, the horizontal component of the movement not well constrained. The SVFS interrupts the continuity of the Eastern Southern Alps thrust fronts in the Veneto sector, suggesting that it played a passive role in controlling the geometry of the active thrust belt and possibly the current distribution of seismic from the Eastern Southern Alps, which is defined kinematically “irksome”. These authorsThis author envisaged a SVF with a sinistral strike-slip faulting style, separating to the west the clockwise rotating Tauern sublid (the crust below the brittle-ductile transition) during the Jura phase (middle-late Miocene). These transcurrent and rotational movements were interpreted to be induced by the NW-SE Adria-Europe convergence along with deep-seated anticlockwise rotation of Adria. The analysis of the Neogene linkage of a set of sinistral strike-slip, N-S inherited Permian to Cretaceous extensional faults conjugate with the SVF has been performed by et al. In this study, the strike-slip kinematics of the SVF north of Posina, where the junction with a set of linked inherited fault occurs, was recognized to have been both dextral (in the Paleogene) and sinistral (in the Neogene), according to the development of a lens-shaped pop-up. This contractional feature has been related to the dextral bend of a sinistral SVF northwards linking with the N-S Trento-Cles fault (TCL in Fig. 1), already suggested by Semenza (1974). model, where intersecting pairs of simultaneously active faults with different sense of shear merge into a single fault via a zippered section. The junction of the three branches would be located at Posina, about 10 km northeast of Schio. The comparison with available analogue models supports a sinistral strike-slip kinematics for the main portion of the SVF from the plain to the Posina triple junction. The


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Many foreland areas in the world display transverse structures accommodating the segmentation of the thrust fronts and the outward propagation of the fold and thrust belts. These structures are commonly pre-existing, steep normal faults penetrating the basement, and originated during previous episodes of extension at various angles to the belts, often reactivated as transpressional or transtensional shear zones. Given their geometry, during the chain shortening these transverse faults are reactivated as strike-slip faults, as for example in the Himalayan foreland (e.g.: Duvall et al., 2020), in the Laramide belt (e.g.: To the south-east of the Euganei Hills, the SVFS continues in the subsurface of the Veneto plain, where it is known as the 75 Conselve-Pomposa fault (CP) (Pola et al., 2014b). Eastward, another buried segment is the Travettore-Codevigo fault (TC; Fig. 1; Pola et al., 2014b).
In the centuries after Schauroth's work only the SVF s.s. has been the subject of many scientific works, and has been cited many times and frequently used in regional tectonic models as a key feature accommodating the indentation of the northern Adria plate margin (e.g. Semenza, 1974;Slejko et al., 1989;Castellarin et al., 2000;Zampieri et al., 2003;Heberer et al., 2017; 80 Mantovani et al., 2020). The work of Pola et al. (2014b) defined for the first time the complex architecture of the whole SVFS.
South of Schio, the SVF is the westernmost strand of a set of buried faults which lies in the subsurface of the Quaternary Veneto plain. North of Schio, near the town of Posina, the SVF joins with a set of N-trending conjugate faults.
Given its geometry and orientation, the most recent activity of the SVFS during the shortening of the Southern Alps was dominated by strike-slip movements. However, the bedrock fault planes of the SVFS are poorly exposed in outcrop, so few 85 kinematic indicators can be found. On the other hand, the seismic sections encountering the strands of the SVFS in the Veneto Plain say little about the strike-slip activity, while showing mainly the extensional character of the former tectonic phases (Pola et al., 2014b). Therefore, the recent kinematics of the SVFS remains unclear. Another puzzling character of the SVFS is the weak seismic activity, which would be expected given the regional role of the fault delimiting the Eastern Southern Alps active and seismogenic thrust fronts (Zanferrari et al., 1982;Galadini et al., 2005;Burrato et al., 2008). Historical and instrumental catalogues show only a scattered distribution of low seismicity along this structure (see Chapter 4). Few instrumental data of the northern part of the area point to a dextral strike-slip activity (e.g. Pondrelli et al., 2006) and consequently, the SVF was recently included in the Italian database of seismogenic source DISS referring to such kinematics DISS Working Group, 2018). In spite of this, most of the geological reconstructions refer to a sinistral strike-slip activity (see Table   1).
Our aim here is to draw the contrasting data and interpretations on the SVFS flourished in the literature spanning a century and a halfSince the literature on SVF and SVFS spans a century and a half, we try to summarize data and interpretations flourished in this long interval of time. First, we briefly outline the geodynamic role, the kinematics, the age of the tectonic phase(s) and where possible, the throw and heave derived from the main papers citing the SVF s.s. or the SVFS. We then review the seismological data and finally we try to interpret all the information in a unifying model, which can reconcile 100 apparently contrasting data.

ID
Year  Table 1: Geological review of more than a century and a half of literature, and synoptic view of the main kinematic parameters of the SVF as proposed by various investigators. At least one third of the authors suggest that a change in kinematics has occurred over time. K: kinematics; N: normal; L: left-lateral; R: right-lateral; N/A: data not available.

2 More than a century and a half of studies
The SVF, being Being the most prominent feature south of the Alps in the Veneto plain ( Fig. 1), the SVF it was drawn in all the geological and structural maps of northeast Italy at various scales. Therefore, the knowledge of the structure is deeply rooted in the geological literature and spans for more than a century and a half (Table 1). While few papers have investigated in detail the structure or part of it, the list of works citing the SVF is very long. Here we shortly examine the main papers,

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books and maps dealing with the SVF with the aim of presenting the evolution of its interpretation, although not giving an exhaustive list. Only recently, due to the availability of subsurface geophysical data, the analysis was extended to buried strands of the whole structure, which consequently was recognizsed as a complex system of faults (SVFS). As a consequence, we will use throughout this section both SVF and SVFS.
The 19 th century geological school of Wien Vienna produced several sound earth scientists studying the Südtirol region, been suspected that these geologists were also military officers with the purpose of knowing the border territories (Scalia, 1917). In fact, although they reported thorough publications on the stratigraphy, palaeontology and tectonics of the Italian territories lying at the southern Austrian border, their geological maps never represented the Austrian side. The first mention 120 of the SVF appeared in the work of the Austrian author Julius Schauroth (1855) on the geological setting of the Recoaro area (Eastern Southern Alps).
Eduard Suess (1875) at page 33 of his book "On the formation of the Alps'' marked the discontinuity of the Tertiary formations at the foot of the southern margin of the Alps in between the towns of Schio and Vicenza, due to a structural rupture. The short citation of the SVF is contained in just a sentence, deriving from the geomorphological prominence of the feature, which has 125 later attracted the attention of a number of geologists. Another Austrian author, Alexander Bittner (1879), suggested that the SVF does not end at Schio, a village lying at the foothills of the Pre-Alps, but was extending within the chain until at least the Borcola pass, 18 km northwestwards. Later-on in the 20 th century the Italian geologists inherited the plentiful literature on the Southern Alps published in the German language. The SVF was then depicted in the geological map of Negri (1901) or referred to as a fault separating abruptly the mountain from the plain, thus with a downthrow of the eastern block (Taramelli, 1882; 130 Molon,1882;Maddalena, 1906). The last author mapped the SVF southeastwards till the Euganei Hills relating their magmatism to the fault, and for the first time recognized also a left-lateral strike-slip movement. The Austrian geologist von Klebelsberg (1918) dedicated his paper to the thesis of the northwestern extension of the fault until the Adige Valley, furthermore to the north than the Bittner (1879) proposal. In addition to vertical offsets of the fault, he also recognized strikeslip movements. In contrast, Fabiani (1925) in his geological map recognised the SVF northern tip near the Borcola Pass.

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The paper from the Italian geologistGeologist De Pretto (1920) added an estimation of the amount of the strike-slip component, showing an important gradient of the offset from 16 km in the southeastern portion (close to Vicenza) to only 2 km close to Schio.
In his monograph on the tectonics of the Lessini Mts., the Austrian geologist Julius Pia (1923)  unravelled a very complicated history of the SVF, with at least four tectogenetic phases. In the first two, the structure acted as a normal fault, accommodating vertical movements produced by the intrusion of respectively felsic magmas, during the Scythian and Anisian, and mafic magmas during the Eocene. A switch of the dip from west to east occurred shifting from the northern sector to the southern sector. In the last two phases of activity, the SVF acted as a left-lateral strike-slip fault in the early-middle Miocene and in the early Pliocene. This kinematics has been related to differential movements of the eastern and western blocks of the fault, in conjunction with gravitational collapse of the sedimentary cover from the Recoaro horst.
From the De Boer work (1963) onwards the literature on the SVF is almost exclusively by the Italian authors. In the sixties the national project on geological cartography at a scale 1:100,000 was in full operation. Therefore, in the sheets 49 Verona (Bosellini et al., 1968) and 36 Schio (Braga et al., 1968), the SVF and the MF were drawn according to the previous literature.
Studying the plain region between the Venice lagoon and the Euganei Hills by means of performanceusing of new seismic lines, Finetti (1972) drew the southern portion of the SVF, as a very steep structure with a Quaternary throw of 200-320 m.
The lowering of the eastern block would be ongoing in the context of the subsidence of the north Adriatic region started since the Eocene.
the two sides of the Italo-Dinaric (now Adria) plate, which was divided into two parts by the structure extending from Cles (north of Trento) to the Dalmatia in the eastern coast of the Adriatic Sea. The left-lateral movement of the SVF was explained by the presence in the western block of rocks deforming in a "ductile" way sandwiched between the "stiff" Adamello pluton and the Athesian platform (the Jurassic Trento platform, partly coinciding with the thick Permian volcanic district). The absence in the eastern block of such soft and rigid rocks would have permitted the northwestwards slip of the eastern side of 165 the SVF.
In the late seventies to early eighties the SVF was investigated in the context of the "C.N.R. Finalized Project Geodynamics -Subproject Neotectonics'' (Barbieri et al., 1981;Zanferrari et al., 1982). The work of Zanferrari et al. (1982) Zanferrari et al. (1982) recognized that in the final Pleistocene to Holocene the SVF accommodated only differential vertical movements of the Lessini Mts.Mountains with respect to the subsiding plain.

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The explanation text of the geological map at a scale 1:10,000 of the Pasubio-Posina-Laghi area from Sedea and Di Lallo (1986) recognizes a Neogene to Quaternary sinistral strike-slip activity of the SVF, with a minimum offset of 3 km.
An Eocene (Lutetian) origin of the SVF was proposed by Doglioni and Bosellini (1987). In two sketches, the fault was represented as a normal fault of a set of ENE dipping faults developed in the eastern margin of the forebulge of the WSW verging Dinaric fold-and-thrust belt.

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The title of a paper from Pellegrini (1988) relies directly on the morphological and neotectonics evidence of the SVF. On the basis of fluvial terraces nesting and stream deviation close to Schio, the author argues that the eastern block of the fault (the plain in between Schio and Vicenza) was lowered during the Quaternary.
The research for the C.N.R. Finalized Project Geodynamics -Subproject Neotectonics led Castaldini and Panizza (1991) to propose an inventory of active faults in between the Po and Piave rivers, where the SVF was classified as "active" within the class "II degree of activity", i.e. with an average slip rate ranging from 0.1 to 1 mm/year, corresponding to a relative lowering of the eastern block in the plain sector. The strike-slip component of the mountainous sector remained controversial. The only portion of this very long structure showing features corresponding to a "I degree of activity" (average slip rate ranging from 1 to 10 mm/year) was referred to as the Malo fault (MF in Fig. 1), a ca. 15 km-long synthetic segment outcropping between Schio and Vicenza.
from the Eastern Southern Alps, which is defined kinematically "irksome". These authorsThis author envisaged a SVF with a sinistral strike-slip faulting style, separating to the west the clockwise rotating Tauern sublid (the crust below the brittle-ductile transition) during the Jura phase (middle-late Miocene). These transcurrent and rotational movements were interpreted to be induced by the NW-SE Adria-Europe convergence along with deep-seated anticlockwise rotation of Adria.

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The analysis of the Neogene linkage of a set of sinistral strike-slip, N-S inherited Permian to Cretaceous extensional faults conjugate with the SVF has been performed by Zampieri et al. (2003). In this study, the strike-slip kinematics of the SVF north of Posina, where the junction with a set of linked inherited fault occurs, was recognized to have been both dextral (in the Paleogene) and sinistral (in the Neogene), according to the development of a lens-shaped pop-up. This contractional feature has been related to the dextral bend of a sinistral SVF northwards linking with the N-S Trento-Cles fault (TCL in Fig. 1), 210 already suggested by Semenza (1974).
Within the neo-Alpine evolution of the Southern Eastern Alps, Castellarin and Cantelli (2000) interpreted the Schio-Vicenza structural system as a sinistral transfer fault system between the Giudicarie belt (inner part of the chain) and the Pedemontana (frontal structure). This contractional deformation (Adriatic compressional event with shortening axis trending WNW-ESE), would be younger than the Serravallian-Tortonian Valsugana event (shortening axis NNW-SSE) and considered mainly Adriatic indenter and the still northward-pushing main body of the Adria plate..
TBy contrast, the Neogene to Present sinistral strike-slip faulting style of the SVF has been attributed once again to its role of western rail of the north Adriatic indenter by Mantovani et al. (20069). This kinematics would have accommodated the decoupling of the Adriatic block from its northwestern (Padanian) protuberance and from Africa, induced by the late Messinian counterclockwise rotation of the Adria plate.

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The computation of the stress and strain from relocated seismic events in the Giudicarie and Lessini Mts.Mountains regions of the Southern Alps permitted Viganò et al. (2008) to define the right-lateral strike-slip activity of the NW-trending faults (parallel to the SVFS). It is worth mentioning that the analyzed events of the Lessini Mts.Mountains fall in the northern sector of the SW block of the SVF (i.e. footwall block; Lessini Mts.Mountains), where the shortening axis is ca. N-S, while in the 230 NE block (Eastern Southern Alps foreland) the shortening axis is NNW-trending. Moreover, in a subsequent paper (Viganò et al., 2015), which include the crustal rheology analysis, the location of the seismicity in the northern part of the Lessini Mts.Mountains has been related to the Verona-Vicenza gravity high anomaly (intrusive and effusive volcanic rocks), which contribute to a stronger lithosphere.
By contrast, the Neogene to Present sinistral strike-slip faulting style of the SVF has been attributed once again to its role of Close to Padova the Euganean hydrothermal system, one of the most important water-dominated low-temperature geothermal 245 systems in Europe (Fabbri et al., 2017), presents the outflow of the hot waters in correspondence of the SVFS, suggesting a structural control. A multidisciplinary study including the analysis of the fracture pattern of a travertine mound, relict of the main outflow which was active until the middle of the 20 th century, before a large exploitation for tourism purposes, has permitted to infer in the subsurface the existence of an extensional relay zone linking two main fault segments of the SVFS Platform. This sharp transition is referred to the sinistral strike-slip Schio-Vicenza-Trento-Cles fault system, which accommodated different amount of shortening due to lateral variation in strength of the Adriatic indenter, related to Permian -

Geological evidence
In this section we present selected geological and geophysical features along the SVFS (Fig. 2) Table   2). These faults belong to the damage zone of the SVF, which is 2-3 km wide (Fondriest et al., 2012) and are interpreted as antithetic Riedel shear fractures . Since their kinematic indicators are sinistral, in this section the SVF is inferred to be dextral.

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Figure 2. Field gGeological and seismic evidence supporting the activity and style of faulting of the SVFS (see Table 2 for details, and central inset for locations). ID 1: vertical fault plane with strike-slip lineations (Borcoletta quarry); ID 2: vertical fault plane with strike-slip lineations (Borcola quarry); ID 3: displaced river terraces crossing the SVF showing the differential uplift of the two blocks separated by the fault (redrawn from Pellegrini, 1988)    The analysis of the longitudinal profiles of the fluvial terraces close to Schio shows Pleistocene differential uplift across the fault system, with the western block (footwall) of the SVF uplifted with respect to the plain (hanging-wall) and accordingly,
To the southeast of the intersection with the frontal thrust of the Eastern Southern Alps, from Schio to Vicenza, the SVF has a prominent surficial expression, since it marks the transition from the eastern border of the Lessini Mts.Mountains block to the foreland basin plain, which is lowered. In between the SVF and the parallel Malo fault (MF), Miocene sediments dip towards the NE, while in some sectors the extensional displacement of the SVF is testified by the presence of a drag folds in 310 the footwall (ID 5 in Fig. 2; IDs 4, 5 and 6 in Table 2; for their location see the central map of Fig. 2). The IDs 4 and 6 can be found in the sheets 36 Schio (Braga et al., 1968) and 49 Verona (Bosellini et al., 1968), respectively, of the 1:100,000 scale Geological Map of Italy (both available from the website of the Italian Geological Survey: http://sgi.isprambiente.it/geologia100k/; last accessed on 27 May 2021). Some seismic sections crossing at high angle the SVFS at a high angle in the plain between Vicenza and Adria (Finetti, 1972;Pola et al., 2014b), two of which we presentare 315 presented in Fig. 2 (IDs 6 7 and 810), highlight the extensional displacement. The total throw of the different sub parallel segments of the SVFS south of Schio is the cumulative expression of the deformation, started from the Mesozoic time in an extensional stress field close to the eastern margin of the Trento platform, and continues to this day in a contractional stress field connected to the flexuring of the foreland (Zanferrari et al., 1982;Pola et al., 2014b).
Obviously, the strike-slip component of the SVF cannot be pointed out by seismic sections but is registered by the analysis of 320 few mesofaults presented in Fig. 2 (IDs 1 and 2) and extracted from the offset of the sedimentary and volcanic formations in geological maps. In the southern section of the SVF, close to the Euganei Hills, a buried relay ramp, kinematically linking the SVF and the CP, has been inferred from the analysis of stratigraphic logs, of gravimetric maps and of the fracture pattern of travertine deposits (Pola et al., 2014a(Pola et al., , 2015. The travertine mound was built by thermal hot water springs, active until the intense exploitation of the second half of the 20th century (Fabbri et al. 2017). Conceptual and numerical modelling of the 325 Euganean geothermal system have corroborated the impact of the structural process driving a local increase in convection and the rising of thermal waters (Pola et al., 2020).

Seismotectonic evidence
Historical and instrumental seismicity in the NE Italy is distributed along the Giudicarie Fault System, the Eastern Southern Alps fronts and the Northern Apennines fronts (e.g. Rovida et al., 2021). The Eastern Southern Alps thrust fronts are bordered 330 to the east by the dextral strike-slip faults of the Dinaric system (Fig. 1) Both these destructive sequences are characterized by multiple similarly large mainshocks and relatively shallow earthquakes (Vannoli et al., 2015).

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The buried outer arc of the Central Southern Alps is connected to the east with the NNE-trending Giudicarie system, that developed along the margin between the Lombardian basin to the west and the Trento platform to the east. This structural system is commonly interpreted as a regional transfer zone between the Central and Eastern Southern Alps (e.g. Castellarin and Cantelli, 2000), and thought to be responsible for the 24 November 2004, Mw 5.0, earthquake (ID 5 in Fig. 1; Pessina et al., 2006)  Besides the relatively well-known shallow thrust sources of the Southern Alps and Northern Apennines, the basement rocks of the Po Plain are cut by deeper inherited faults, that formed during the Mesozoic extensional phases preceding the inception of the Africa-Eurasia relative convergence (e.g. Scardia et al., 2015). As testified by the 1117 and the 13 January 1909, Mw 5.4, events, significant earthquakes may be generated by this set of elusive, inherited structures, that are reactivated in the 360 present-day tectonic compressional regime as reverse or strike-slip faults (Vannoli et al., 2015). In particular, the 1909 earthquake had a macroseismic epicenter located south of Ferrara and affected a very large area with slight to moderate damages (Rovida et al., 2021). This macroseismic scenario was interpreted as caused by the significant depth of the event (Meloni and Molin, 1987;Faccioli, 2013;Vannoli et al., 2015), and, as suggested by Sbarra et al. (2019), it may have occurred well below the basal detachment of the Northern Apennines outer fronts at a depth of 41 km, with a recalculated Mw of 6.2.
the sources of the most dangerous earthquakes of the Po Plain and surrounding areas, having magnitude comparable or larger to those associated with the active thrusts (e.g. Scardia et al., 2015).
According to the historical seismic catalogues (Guidoboni et al., 2018(Guidoboni et al., , 2019Rovida et al., 2021), during the last millennium the SVFS did not generate earthquakes larger than magnitude 5.0. As a matter of fact, the cities of Vicenza and Padova, which are located very close to the SVFS (Fig. 1), have a long and well documented "seismic history", i.e. list of effects in terms of macroseismic intensities that affected the two localities, with well-distributed observations over the last millennium, both starting with the 1117 earthquake, and even if they have rarely experienced damage due to large earthquakes (Rovida et al., , 2021 (Rovida et al., 2021). The local earthquakes (i.e. located close to the towns) are labeled in bold and highlighted filled 385 with by a red pattern circle (see text for detail). The SVFS is the only known active fault system in the area, and for this reason we suggest that presumably have caused these local earthquakes.
The known earthquakes responsible for the most serious damage in the study area were the 1117, Mw 6.5, Veronese, the 1348, Mw 6.6, Alpi Giulie, and the 1695 Mw 6.4, Asolano events (Fig. 3); their causative faults are far from the SVFS, and do not belong to it. However, numerous historical earthquakes were felt exclusively in Vicenza or Padova, and most likely were 390 generated by local sources (i.e. located close to the towns), potentially belonging to the SVFS (Fig. 4a). These low-magnitude historical earthquakes, listed and marked with an "X" in the last column of the Table 3 and labeled in bold in Fig. 3 Fig. 3. The table shows their macroseismic intensities, total number of available macroseismic data points (N), and moment magnitude (Mw). Historical earthquakes whose causative faults could presumably be the SVFS are shown with a "X" in the last column; a dash in this column indicates that no association has been made. The 1117 earthquake that is associated with the highest MCS intensity in Padova and Vicenza is not included in this table because its epicenter is located far away from the SVFS.  (Rovida et al., 2021), is the work by Caracciolo et al. (2009). The instrumental epicenter is shown with a red star, coincides with the macroseismic one, and falls near the SVFS. Due to its location, one of the mapped faults belonging to the SVFS may be the source of this earthquake (see text and 410 Table 3). (b) Map showing the largest instrumental earthquakes of the study area with red stars (see Table 4). Focal mechanisms from EMMA Database and other sources (Vannucci and Gasperini, 2004;Slejko and Rebez, 1988;Slejko et al., 1989;Pondrelli et al., 2006;Viganò et al., 2008). Earthquake relocations from Viganò et al., 2015. The locations of the geological evidence are shown in green (see Table 2 Instrumental catalogues show that the SVFS area is affected by low seismic moment release, with most of the events located in its northern mountainous portion, north of Schio ( Fig. 4b and Table 4), and have hypocentral depths ranging between 2 and 19 km (Viganò et al., 2008;Moratto et al., 2017). Their moment magnitude ranges between 3.3 and 4.9. The 13 September 420 1989, Mw 4.9, earthquake (ID 4 in Table 4 and Fig. 4b) is the largest instrumental event that affected the study area in instrumental times, and we consider it as representative of the local kinematic style of faulting of the SVFS. The macroseismic effects of this event are documented by 779 intensity points spread over a wide area covering the Southern Alps and the Po and Veneto plains (Rovida et al., 2021). The epicentral intensity of the 1989 shock is VI-VII MCS, and the area of greatest damage lies in the Giudicarie-Lessini region, north of the locality of Posina. The focal mechanism of the 1989 event is strike-425 slip (Eva and Pastore, 1993;Pondrelli et al., 2006;Viganò et al., 2008), and the direction of its maximum horizontal compressive stress is compatible with right-lateral strike-slip activation of a NW-SE trending fault belonging to the northern portion of the SVFS (Viganò et al., 2008;Vannoli et al., 2015;Restivo et al., 2016).
All available focal mechanisms of the study area consistently show right-lateral strike-slip over the northern portion of the SVFS (Table 4 and Fig. 4b; Vannucci and Gasperini, 2004;Viganò et al., 2008).

Discussion
The SVFS has been active with different tectonic phases and different kinematics at least from the Mesozoic (Table 1). Its most prominent segment, the SVF s.s., is an inherited and well-developed morphotectonic element with a significant imprint in the landscape, reactivated in the current stress regime as testified by the moderate seismicity along its northern portion (Table 4), and the travertine recent deposits in its central section (ID 8 in Fig. 2 and Table 2; Pola et al., 2014a). Further  Table 3).
Looking at the geological and geophysical evidence south of Posina (IDs 3 to 9 of Fig. 2 and Table 2) some consistent conclusions may be drawn about the geodynamic role, the recent activity and style of faulting of the SVFS. Pleistocene differential vertical movements across the fault system occurred close to Schio, as shown by the differential uplift of the 445 western block (footwall) of the SVF with respect to the plain (Pellegrini, 1988;ID 3). Accordingly, in the early Pliocene marine conditions were present in the eastern block of the fault, while continental conditions characterised the western block (Zanferrari et al. 1982). The same evidence is shown by the attitude of Miocene sediments along the northern part of the SVF between Schio and Vicenza, where the deposits dip 50° towards northeast, being the limb of a drag fold in the footwall of an extensional fault (IDs 4 to 6). The same structure is recognizable in some seismic sections sub-orthogonal to the SVF (Pola et (Table 1).
However, the few instrumental seismological data recorded near the SVF northwesternmostnorthwestern most part (north of 460 Posina), point to a dextral strike-slip activity (Pondrelli et al., 2006(Pondrelli et al., , 2020Viganò et al., 2008Viganò et al., , 2015. In addition, the northwestern part of the SVF, close to the Borcola Pass, subvertical conjugate fault planes crop out in two quarries exploiting Upper Triassic dolomitic marbles produced by intrusion of basaltic dykes. , and The wide slickensides show sub-horizontal mega-corrugations produced by nearly pure sinistral strike-slip movements (IDs 1 and 2 of Fig. 2 and Table 2). The analysis of one of such conjugatethe kinematic indicators suggests a sinistral activity of these N-S faults , which has permitted to infer 465 a dextral kinematics for the SVF (Fondriest et al., 2012) (Fondriest et al., 2012). Therefore, this review of published papers presents a prominent problem about interpretation of the recent strike-slip sense of motion of the SVF, which is described as sinistral (in most cases), but also as dextral (Tables 1 and 2). A model to solve the apparently conflicting data must be found considering the complexity and the 3D structure of the SVFS, which is more than a straight line as usually drawn in the structural maps.

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If we look at the plan view geometry of the SVFS in the chain sector (north of Schio), we observe a junction with the Gamonda fault (GF) close to Posina, ca 10 km northwest of Schio (Fig. 5;Sedea and Di Lallo, 1986;Zampieri et al., 2003;Massironi et al., 2006;Zampieri and Massironi, 2007). The NW-trending SVF and the NNE-trending GF depicts a Y-type triple junction, with transport direction at a high-angle to the branch line, which is sub-vertical. This classification derives from the very As a matter of fact, the opening zipper model shows right-lateral motion north of Posina and left-lateral motion to the south as well as along the N-S segments (Zampieri and Massironi, 2007), in agreement with the available focal mechanisms of the largest earthquakes and to the kinematic model presented by Serpelloni et al. (2016, see Fig. 8). Furthermore, the left-lateral 495 kinematics of the SVFS up to the Posina triple junction at the regional scale is also in agreement with the geodynamic model of the Adria plate indentation (see Fig. 7), while the zipper structure represents a local feature due to the back-stop of the Giudicarie thrust front (see also Verwater et al., 2021 for an alternative interpretation). The space problem produced by the intersection of simultaneously active faults with opposing slip sense can be solved by splitting (or unzippering) the merged fault (inspired by Zampieri et al., 2003;Zampieri and Massironi, 2007; inset of the right corner from Passchier and Platt, 2017 (Fedorik et al., 2019, Fig. 15) produces some Riedel shear faulting and is dominated by two major steep strike-slip faults having also a normal dip-slip component. The last stage of deformation also shows the linkage between the strike-slip dominated fault zone and the forethrust by evolving with development of an oblique thrust the propagation of the sub-vertical strike-slip principal fault zone, which crosscuts the fore thrust (Fig. 6). This transtensional 515 setting resembles very closely to the real structure composed by the SVF and the Eastern Southern Alps thrust front. In fact, the northern Adria plate is pushing with a NNW direction against the Alpine belt, with a small angle with respect to the NWtrending SVF (see Figs. 1 and 7), and the kinematic modeling of the GPS data shows an expected transtension on the SVF (Serpelloni et al., 2016) in agreement with the dip-slip displacement shown by the available seismic sections crossing the SVFS (Fig. 2). Besides, the kinematics and the relative position of the strike-slip faults with respect to the chain front are 520 similar in both real geology and the models. The only difference of the analogue modelling with respect to the real structure is the timing of the deformation phases. In the models the thrust belt development predates the strike-slip activation in the foreland, while in the study area the development of the SVF predates that of the frontal thrusts of the chain. However, the SVF activity continues after the thrust formation and the interaction between the two structures is very similar to the model.
In fact, the buried TB fault, which connects obliquely the PE thrust with the SVF (Figs. 6a and 6b) was reproduced by the 525 models and corresponds to the new thrust front of the Fig. 6c. The similarity of the analogue modelling of Fedorik et al. (2019) with the real setting of the study area strongly supports the interpretation of the SVFS south of Schio as a sinistral strike-slip fault. The meaning of the SVFS in the framework of the regional tectonics and its long-lived history is shared with other fault systems found in the thrust belt and foreland of the central and southern Apennines and Sicily. These shear zones are inherited structures reactivated in the current stress regime driven by the plate convergence, and can host the sources of moderate to large 550 earthquakes (e.g. Tavarnelli et al., 2001;Butler et al., 2006;Di Bucci et al., 2010). The most important of them are: (a) the Mattinata-Gondola fault system in the Gargano area, a segment of which located along its western prolongation generated the  (Tavarnelli et al., 2001;Butler et al., 2006;Bonini et al., 2019;Vannoli et al., 2021). All these fault systems, during their long history, have seen different tectonic phases often characterised by opposite sense of shear (e.g. first right-lateral strike-slip, then left-lateral strike-slip or vice-versa). As a consequence, as seen during the 1990 and 2002 seismic sequences, they these inherited fault systems are generally often characterised by low energy release mechanisms, with low stress drops and, consequently, small coseismic slip , as seen during the 1990 and 2002 560 seismic sequences (Calderoni et al., 2010). In generaladdition, these large long-lived shear zones located in the foreland areas

Commentato [PB4]:
We modified the figure adding the inset in the lower right corner, showing the regional geodynamic framework of the Adriatic indenter.
are responsible in Italy for the largest seismic release outside the better known active thrust and extensional belts, and play a primary role in the seismotectonics of the central Mediterranean region (DISS Working Group, 2018).
The Adriatic plate indenter has been considered as delimited by the Giudicarie fault system to the west, the Pustertal-Gailtal fault to the north (Ratschbacher et al., 1991;Reiter et al., 2018;Rosenberg et al., 2004;Rosenberg et al., 2007) and the Dinaric 565 fault system to the east (Mantovani et al., 2006;Massironi et al., 2006;Heberer et al., 20167;Brancolini et al., 2019). In this context, the SVFS represents an intraplate structure crossing the Mesozoic Trento platform. However, since the late Messinian the Adriatic block decoupled from its nearly stationary northwestern (Padanian) protuberance and the western indenter margin widened incorporating the SVFS, while leaving outside the contractional deformation the Lessini-Berici-Euganei foreland block (Mantovani et al., 2006;Massironi et al., 2006;Mantovani et al., 2006), which represents an anomalous tectonic feature 570 separating the Western Southern Alps from the ESA and the related forelands (Laubscher, 1996). In fact, tectonic balancing of cross sections parallel to the local NNW-SSE shortening direction has suggested that the ESA comprise two kinematic domains that accommodated different amount of shortening during overlapping times (Verwater et al., 2021). These two domains are separated by the Trento-Cles -Schio-Vicenza fault systems, which offsets the ESA front in the south, while merging with the Northern Giudicarie fault to the north (Fig. 1). The east-west lateral variation of shortening across the 575 Giudicarie Belt indicates internal deformation and lateral variation in strength of the Adriatic indenter related to Permian -Mesozoic tectonic structures and paleogeographic domains (Verwater et al., 2021).

Conclusions
In the northern part of the Adria plate the transverse structure of the SVFS has been active with different tectonic phases and different kinematics at least from the Mesozoic. Nowadays, its westernmost segment (SVF s.s., i.e. the segment from the Adige

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Valley to the Euganei Hills) is an inherited and well-developed structural element with a significant imprint in the landscape, reactivated in the current stress regime. If the long-term dip-slip component of faulting is evident on the SVF and on other buried segments of the fault system, on the contrary, the horizontal component of the movement is not well constrained although it could have accrued accommodated a total of a few kilometers of displacement with sinistral motion (Table 1).
Unfortunately, apart from the moderate instrumental seismicity near its northern end, the moderate historical seismicity near 585 its central sector, and the geological evidence of recent deformation of a travertine mound close to the Euganei Hills, there is little evidence to constrain the recent activity of the SVFS, and even its role in the geodynamic framework of the Southern Alps is still a matter of debate. Although its kinematics is still largely unknown, we observe that it interrupts the continuity of the Southern Alps thrust fronts in the Veneto sector, and controls the forward propagation of the thrusts, suggesting that it played a key passive role in controlling the geometry of the active fault systems and the current distribution of seismic release.

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As a matter of fact, the true kinematics of this fault system is ambiguous, since the instrumental data along the northernmost part (to the north of Posina) of the SVFS point to a dextral strike-slip activity. The most important event is the 13 September 1989, Mw 4.9 earthquake, located north of Schio. However, geodynamic considerations point to a role for the SVFS similar to that of the Dinaric system being presently characterized by dextral strike-slip faulting, and accommodating to the east the indentation of Adria against the Alpine chain (Fig. 7). If so, the SVFS on the whole should have a sinistral component of 595 motion. While further evidence on the kinematics of the SVFS shall arise solely from the results of further research in the area, the apparently conflicting data can be reconciled in the sinistral opening "zipper" model, where intersecting pairs of simultaneously active faults with different sense of shear merge into a single fault via a zippered section. The junction of the three branches would be located at Posina, about 10 km northeast of Schio. The comparison with available analogue models supports a sinistral strike-slip kinematics for the main portion of the SVF from the plain to the Posina triple junction. The debate on the strike-slip kinematics of the SVF has been tentatively solved and seems to work unless new data will threaten the model presented here.
The SVF does not appear to have generated earthquakes larger than magnitude 5.0. Moderate instrumental seismicity is clustered in the northern portion of this structure, and historical catalogues show a scattered distribution of low-magnitude earthquakes along its central and southern portions. However, the set of geomorphological, structural and geodynamic features 605 suggest that individual segments of the SVFS may host significant (M 5.5+) earthquakes. As discussed in chapter 4, the causative fault of the largest known earthquake of the Po Plain, the 1117 Mw 6.5 Veronese earthquake, is believed to be a longlived, inherited fault cutting the foreland.
Therefore, although the earthquake potential of the SVFS is still uncertain, and need to be fully characterised, these long-lived transverse structures cutting through the foreland, such as the SVFS, may represent a substantial, and still poorly recognised 610 source of seismic hazard for the area.

Author contribution
All the authors shared the conceptualization of the manuscript and its preparation.