Décollement depth versus accretionary prism dimension in the Apennines and the Barbados

Bigi, Sabina; Lenci, F.; Doglioni, Carlo; Moore, J. Casey; Carminati, Eugenio; Scrocca, Davide

doi:10.1029/2002tc001410

Cited by 30 publications

(19 citation statements)

References 59 publications

(97 reference statements)

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“…Furthermore, although the Apennines accretionary prism mainly involves the sedimentary cover, in the Apennines the basal decollement depth shows a great variability (Figure ). The deepest depths are recognized in the north, becoming shallower in the southern part of the chain (Bigi et al, ). The Calabrian arc is characterized by shallower depths than the Apenninic region (Maesano et al, ; Polonia et al, ).…”

Section: Discussionmentioning

confidence: 99%

The Decollement Depth of Active Thrust Faults in Italy: Implications on Potential Earthquake Magnitude

2019

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Thrust fault ruptures during earthquakes do not often propagate down to the brittle‐ductile transition. Lithological variations control the behavior and depth of regional basal thrusts and decollement planes. Thrust fronts may be discontinuous along strike, limiting the dimension of single coseismic ruptures. These factors control the maximum expected magnitude in one region. This is the case of Italy where the convergence of few millimeter per year in the Apennines accretionary prism and along the retrobelt of the Alps generates compressional earthquakes with moderate to strong magnitudes. Here, using geological and geophysical data, we first compile a map of the undulated active basal thrust decollement for Italy that occurs from 1 to 17‐km depth. Then, we verify the relationship between the length of seismogenic ruptures in thrust faults (Lf) and the maximum depth of thrust faulting (zmax) of related earthquakes and find that their ratio (Lf/zmax) ranges between 2 and 4. Finally, we compute the potential seismogenic volume and estimate the maximum magnitude using an empirical relationship that multiplies the decollement depth and the Lf/zmax ratio. Maximum calculated magnitude is 6.7 ± 0.37 (depending on Lf/zmax and fault dip angle), consistent with the largest magnitude of thrust‐related earthquakes recorded in Italy (6.5–7.0). Lower magnitudes are predicted in the Ionian Seas at the external front of the Apennines where smaller crustal volumes are involved, whereas higher magnitudes are expected in the southern Po Basin, the western Adriatic Sea, Sicily offshore, and the Southern Alps where the decollement is deeper and the brittle volumes are far greater.

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Section: Discussionmentioning

confidence: 99%

The Decollement Depth of Active Thrust Faults in Italy: Implications on Potential Earthquake Magnitude

2019

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“…As a consequence, the rate at which topography is created can differ, i.e., the effect of an unbalanced internal state of stress might vary in time and in distinct sectors of the orogen itself. For instance, the wedge net elevation is a function of its position with respect to the down going plate curvature [ Bigi et al , 2003] and the rheology of the subducting plate [ Wang , 2001]. The question now arises as to how the wedge dynamically responds to this transition.…”

Section: Discussionmentioning

confidence: 99%

Effect of unbalanced topography and overloading on Coulomb wedge kinematics: Insights from sandbox modeling

2004

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[1] This study addresses the effect of variable unbalanced topography and overload on the kinematics of a fold and thrust belt developed within a collisional belt that underwent a subduction polarity reversal event. This was done by physical modeling of doubly vergent Coulomb wedges, using sand as an analogue material. During the experimental procedure a preexisting topography was generated by a first phase of subduction in one direction. A second phase of subduction was then initiated in the opposite direction (simulating a subduction flip). An anomalous, strong frontal growth for the wedge during the second phase was experimentally shown to be dependent upon surface slope breaks and the critical asymmetrical architecture achieved by the wedge at mature stages of deformation. The latter is suggested to be the rule for doubly vergent orogens at steady state, even after a subduction flip. During the experiments, surface processes, like syntectonic erosion and sedimentation, markedly altered mass transfer within the wedge. In particular, lowering the surface slope by syntectonic erosion favored cycling between accretion and underthrusting modes. By contrast, a sudden syntectonic sediment load in the prowedge region promoted prolonged phases of underthrusting, retarding accretion of new imbricates at the prowedge toe. However, at later stages of deformation the prowedge was forced to regain its characteristic minimum critical taper as predicted by theory and did so by the sudden nucleation of long, flat thrust units, rapidly rebalancing the asymmetry between prowedge and retrowedge regions. The experiments suggest that given a fixed critical taper related to time-invariant frictional properties along the wedge bounding surfaces, deformation does vary within the wedge according to time-varying location of normal stress surpluses and unbalanced topography acting on potential failure surfaces. These, in turn, alter the equilibrium between prowedge and retrowedge basal detachments that is here considered to be a major factor controlling the self-regulating dynamics of collisional orogens.

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“…During the subduction hinge rollback, the Meso‐Cenozoic passive margin sedimentary cover of the subducting Adriatic plate was offscraped and piled up to form the Apennines accretionary prism. The depth of the basal décollement plane at the front of the Apennines accretionary wedge varies significantly (3–10 km) moving along strike [ Bigi et al , 2003; Lenci et al , 2004]. In addition, the foreland regional monocline shows variable dips along the belt [ Mariotti and Doglioni , 2000].…”

Section: Geological Settingmentioning

confidence: 99%

Compaction‐induced stress variations with depth in an active anticline: Northern Apennines, Italy

2010

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[1] It is shown that the stress field can vary with depth, even within a homogeneous tectonic setting, as documented for the active Mirandola fault-related fold along the buried front of the northern Apennines. Analyses of borehole breakouts and other well data, integrated with seismological information and field evidence, show that extension perpendicular to the fold axis, above approximately 1200 m, changes to a strike-slip stress field and finally to compression near the main detachment at depth. Similar along-depth strain variations recognized in non-active anticlines are usually explained by invoking tangential longitudinal strain folding (i.e., stretching above and shortening below a neutral surface) or gravitational instabilities. However, in this study, we propose that differential compaction may play a significant and generally overlooked role. With the aid of numerical modeling, it is shown that where fold limbs are onlapped by highly compactable deposits (as in the Mirandola area), differential compaction induces stretching at shallow (<1-2 km) depths. The amount of stretching is a function of the shape of the fold and of the thickness of the syn-tectonic sediments. We conclude that in the Mirandola case study, the stress variations observed with depth are the result of a combination of a regional compression at depth and local tension driven by differential compaction of growth strata on the limbs of the anticline with respect to its crest.

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Décollement depth versus accretionary prism dimension in the Apennines and the Barbados

Cited by 30 publications

References 59 publications

The Decollement Depth of Active Thrust Faults in Italy: Implications on Potential Earthquake Magnitude

The Decollement Depth of Active Thrust Faults in Italy: Implications on Potential Earthquake Magnitude

Effect of unbalanced topography and overloading on Coulomb wedge kinematics: Insights from sandbox modeling

Compaction‐induced stress variations with depth in an active anticline: Northern Apennines, Italy

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