Tectonics and seismicity in the Northern Apennines driven by slab retreat and lithospheric delamination

D'Acquisto, Mario; Zilio, Luca Dal; Molinari, Irene; Kissling, Edi; Gerya, Taras; Dinther, Ylona van

doi:10.1016/j.tecto.2020.228481

Cited by 18 publications

(14 citation statements)

References 74 publications

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“…Some others exhibit, like the Himalaya, a duplex system and antiformal culmination in the inner wedge: These example include the Pyrenees (e.g., Martínez & Vergés, 1988) and the Apallachians (e.g., Kulander & Dean, 1986) (Figure 1). Such crustal‐scale geometry is relatively generic because, as seen in numerical experiments accounting for a realistic geometry and rheological layering at the lithospheric scale (e.g., D'Acquisto et al, 2020; Dal Zilio, Kissling, et al, 2020; Selzer et al, 2008), (1) the thrust fault system must at some point root in a zone of thermally activated ductile deformation forming a deep‐seated décollement and (2) décollement levels naturally form at shallower depth either at the contact between the sediments and the crystalline basement or within the sedimentary cover. These shallower décollements might appear weak due to particularly weak lithologies prone to ductile deformation under low shear stress, as is the case for the evaporite layers in the Jura Mountains (e.g., Sommaruga, 1999).…”

Section: Discussionmentioning

confidence: 99%

Structural Evolution of Orogenic Wedges: Interplay Between Erosion and Weak Décollements

2020

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Orogenic wedges commonly display an inner wedge, where crystalline units have been exhumed, and an outer wedge formed by imbricated sedimentary units detached from the basement. Analog experiments have shown that similar structures can emerge naturally in the presence of weak décollements due to the interplay between erosion and deformation. In this study, we further investigate this hypothesis using two-dimensional, visco-elasto-plastic numerical models. Our experiments assume a basal and an intermediate décollement within the wedge. Experiments with a frictional strength of the basal décollement lower or equal to that of the intermediate décollement show a structural evolution of fold-and-thrust belts dominated by out-of-sequence thrusting. Conversely, when the intermediate décollement is weaker than the basal décollement, distinct outer and inner wedges are formed. This process leads to episodic migration of midcrustal ramps, tectonic underplating, and antiformal stacking facilitated by erosion. Comparison between our models and the Himalayan wedge suggests a low effective friction (∼0.10), which is probably due to dynamic weakening during large (M8+) Himalayan earthquakes. The deeper décollement, along which the lower plate thrusts beneath the High Himalaya, must be a thermally activated ductile shear zone with an apparent friction of ∼0.18. Fold-and-thrust belts worldwide exhibit various architectures in which different décollement levels might be activated. Thus, our study provides a framework to help assess under which conditions a variety of structures observed in orogenic systems can arise.

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Section: Discussionmentioning

confidence: 99%

Structural Evolution of Orogenic Wedges: Interplay Between Erosion and Weak Décollements

2020

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“…This so-called SRO model offers an explanation for the ensemble of observations extracted from the Central Alps (Kissling & Schlunegger, 2018), including (1) the stacking of nappes (Fry et al, 2010), (2) the force balance with the thick and buoyant crustal root, (3) the postcollisional evolution of the Molasse foreland basin (Schlunegger & Kissling, 2015), and (4) the current seismicity pattern in the Central Alps (Singer et al, 2014). Notably, slab retreat and upper mantle confined dynamics are features commonly found in other postcollisional convergent margins, including the Apennines (e.g., Carminati et al, 2003;D'Acquisto et al, 2020) and in most of the circum-Mediterranean arc (Brun & Faccenna, 2008;Faccenna et al, 2004;Jolivet et al, 2013;Royden, 1993). In light of these results, while the evolution of the Himalayas serves as a much better example where mountain building processes and collision are ongoing, the understanding of the recent geologic history of the Central Alps requires an alternative view.…”

Section: Discussionmentioning

confidence: 99%

Slab Rollback Orogeny Model: A Test of Concept

Zilio

Kissling

Gerya

et al. 2020

Geophysical Research Letters

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Buoyancy forces associated with subducting lithosphere control the dynamics of convergent margins. In the postcollisional stage these forces are significantly reduced, yet mountain building and seismicity are ongoing, albeit at lower rates. We leverage advances of a newly developed seismo-thermo-mechanical modeling approach to simulate tectonic and seismicity processes in a self-driven subduction and continental collision setting. We demonstrate that the rearrangement of forces due to slab breakoff, in the postcollisional stage, causes bending and rollback of the residual slab, suction forces, and mantle traction at the base of the upper plate, while stress coupling transfers to the shallow crust. Our results provide an explanation for the postcollisional evolution of the Central Alps, where the so-called Slab Rollback Orogeny model explains the slow yet persistent upper plate advance, the height of the mountain range, and a seismicity pattern consistent with the different tectonic regimes throughout the orogen. Plain Language Summary A long-standing debate in tectonophysics evolves around whether vertical or horizontal forces are the primary drivers of mountain building processes. Here we explore this problem using 2-D numerical models in a generic subduction and continental collision setting. Our results show how the postcollisional evolution of the orogen is controlled by a slow, but persistent, sinking and bending of the postbreakoff residual slab. The resulting seismicity pattern shows a broad pattern of different style of faulting, which are consistent with the local tectonic regimes. We find good correlations between our numerical results and the previously conflicting tectonic observations in the Central Alps and the adjacent foreland basin. Our results thus support the hypothesis that the postbreakoff remaining slab exerts a first-order control on the motions and deformations of collisional orogens.

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“…The Neogene-to-recent tectonic evolution of the Apennines has been characterized by contractional tectonic activity in the foreland, accompanied by extension in the internal domain [22][23][24]. This deformation has produced a great density and variety of fault systems with different kinematics, which may be seen as defining different morphostructural domains (Figure 1), as described below [25][26][27][28][29]. [30,31], and earthquakes and focal mechanisms are from the INGV archive [2,32].…”

Section: Main Structural Domains In the Northern Apenninesmentioning

confidence: 99%

“…Recent seismicity, including the 2012 Emilia Mw 5.9 thrust earthquake [4,33], along with geomorphic studies [29], clearly show that folding and thrusting associated with the ADF are currently active. The Apennines Range Front [25,[27][28][29] lies some 60 km to the southwest of the ADF. The ARF front is marked by a transition from gently dipping alluvial strata in the Po basin to uplifted bedrock in the Apennines, presently standing up to 2000 m above the Po plain near the orographic divide.…”

Section: Main Structural Domains In the Northern Apenninesmentioning

confidence: 99%

“…The studied area is dominated by shallow earthquakes of low to moderate magnitude and normal to oblique focal mechanisms [1,2,4,27,[115][116][117][118]. Figure 12 reports instrumental earthquakes with magnitude Mw >1 and historical earthquakes derived from the CPTI15 v.3 catalog [35,37].…”

Section: Historical and Instrumental Seismicity Within The Investigated Areasmentioning

confidence: 99%

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Active Fault Systems in the Inner Northwest Apennines, Italy: A Reappraisal One Century after the 1920 Mw ~6.5 Fivizzano Earthquake

et al. 2021

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Based on the review of the available stratigraphic, tectonic, morphological, geodetic, and seismological data, along with new structural observations, we present a reappraisal of the potential seismogenic faults and fault systems in the inner northwest Apennines, Italy, which was the site, one century ago, of the devastating Mw ~6.5, 1920 Fivizzano earthquake. Our updated fault catalog provides the fault locations, as well as the description of their architecture, large-scale segmentation, cumulative displacements, evidence for recent to present activity, and long-term slip rates. Our work documents that a dense network of active faults, and thus potential earthquake fault sources, exists in the region. We discuss the seismogenic potential of these faults, and propose a general tectonic scenario that might account for their development.

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Tectonics and seismicity in the Northern Apennines driven by slab retreat and lithospheric delamination

Cited by 18 publications

References 74 publications

Structural Evolution of Orogenic Wedges: Interplay Between Erosion and Weak Décollements

Structural Evolution of Orogenic Wedges: Interplay Between Erosion and Weak Décollements

Slab Rollback Orogeny Model: A Test of Concept

Active Fault Systems in the Inner Northwest Apennines, Italy: A Reappraisal One Century after the 1920 Mw ~6.5 Fivizzano Earthquake

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