Imaging Alpine crust using ambient noise wave-equation tomography

Lu, Yang; Stehly, Laurent; Brossier, Romain; Ambert, Paul

doi:10.1093/gji/ggaa145

Cited by 43 publications

(53 citation statements)

References 98 publications

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“…To the east of the exhumed mantle wedge, in the light of the deep tectonic structure revealed by recent tomography models that document steeply dipping NNW‐SSE faults in correspondence with observed earthquake alignments (e.g., Lu et al, 2020; Solarino et al, 2018), focal mechanisms are supportive of a kinematic framework that is relatively constant with depth, and invariably dominated by left‐lateral motion and local shortening (Figure 6). To the west and on top of the exhumed mantle wedge, the seismic style is dominated by reverse mechanisms in the 12–30 km depth range, and by normal to oblique‐normal mechanisms in the 0–12 km depth range (Figure 6).…”

Section: Discussionmentioning

confidence: 73%

Seismotectonics at the Transition Between Opposite‐Dipping Slabs (Western Alpine Region)

2020

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We analyze a fully reprocessed data set of~9,000 seismic events recorded in the western Alpine region during the past 30 yr, in order to understand how convergence between Africa and Eurasia is presently accommodated at the transition between the opposite-dipping Alpine and Apenninic slabs. We confirm that seismicity in the Internal Zone of the Western Alps is clustered along two different arcs (Briançonnais and Piedmont arcs), clearly outlined by events in the 0-12 km depth range. The Piedmont Arc is best outlined by events in the 12-30 km depth range, forming a narrow belt that matches the shape and location of the Ivrea gravity anomaly. In the Internal Zone, σ 3 , is oblique to the orogen trend. Although the mountain range is spreading gravitationally at a shallow level, spreading occurs intermittently with other earthquakes that are more directly related to plate interactions. Strike-slip solutions are predominant for events of magnitude M l > 4, and reverse solutions are dominant along the Piedmont Arc for events of magnitude M l < 4. Nodal planes have dominant NNW-SSE and ENE-WSW orientations that are common to major faults mapped in the study area. Integration with available tectonic and geodynamic constraints indicates that lithology distribution in the subduction wedge, orientation of major faults within and outside the subduction zone, and the exhumation of mantle rocks at shallow depth concurrently determine a complex seismotectonic scenario that may be expected in other subduction zones worldwide.

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Section: Discussionmentioning

confidence: 73%

Seismotectonics at the Transition Between Opposite‐Dipping Slabs (Western Alpine Region)

2020

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“…Taking the average crustal Poisson ratio of 0.256 (Christensen, 1996) into account, the S-wave threshold velocity is 4.3 km (An et al, 2015). In some part of the study region (i.e., beneath the Southeastern Alps) the Moho is deeper than 55 km which is close to the maximum depth of SEA-Crust (Molinari and Morelli, 2011;Spada et al, 2013;Bianchi et al, 2015;Hetényi et al, 2018b;Kästle et al, 2018;Lu et al, 2018Lu et al, , 2020Stipčević et al, 2020). Therefore, in these regions, SEA-Crust is not able to sample the shallow uppermost mantle beneath such a deep Moho and the 1D velocity models vary smoothly with depth, especially toward the deepest parts.…”

Section: Crystalline Basement and Moho Depthmentioning

confidence: 94%

“…A recent joint inversion of surface wave phase velocities from ambient noise and earthquakes confirmed the heterogeneity of the crustal structure between the Central and Eastern Alps (Kästle et al, 2018). New crustal models from ambient noise tomography have also been recently proposed by Lu et al (2020), Molinari et al (2020), Qorbani et al (2020) improving the resolution of the existing reference models like EPcrust (Molinari and Morelli, 2011).…”

Section: Introductionmentioning

confidence: 93%

High-Resolution Crustal S-wave Velocity Model and Moho Geometry Beneath the Southeastern Alps: New Insights From the SWATH-D Experiment

Sadeghi-Bagherabadi

Vuan

Aoudia

et al. 2021

feart

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We compiled a dataset of continuous recordings from the temporary and permanent seismic networks to compute the high-resolution 3D S-wave velocity model of the Southeastern Alps, the western part of the external Dinarides, and the Friuli and Venetian plains through ambient noise tomography. Part of the dataset is recorded by the SWATH-D temporary network and permanent networks in Italy, Austria, Slovenia and Croatia between October 2017 and July 2018. We computed 4050 vertical component cross-correlations to obtain the empirical Rayleigh wave Green’s functions. The dataset is complemented by adopting 1804 high-quality correlograms from other studies. The fast-marching method for 2D surface wave tomography is applied to the phase velocity dispersion curves in the 2–30 s period band. The resulting local dispersion curves are inverted for 1D S-wave velocity profiles using the non-perturbational and perturbational inversion methods. We assembled the 1D S-wave velocity profiles into a pseudo-3D S-wave velocity model from the surface down to 60 km depth. A range of iso-velocities, representing the crystalline basement depth and the crustal thickness, are determined. We found the average depth over the 2.8–3.0 and 4.1–4.3 km/s iso-velocity ranges to be reasonable representations of the crystalline basement and Moho depths, respectively. The basement depth map shows that the shallower crystalline basement beneath the Schio-Vicenza fault highlights the boundary between the deeper Venetian and Friuli plains to the east and the Po-plain to the west. The estimated Moho depth map displays a thickened crust along the boundary between the Friuli plain and the external Dinarides. It also reveals a N-S narrow corridor of crustal thinning to the east of the junction of Giudicarie and Periadriatic lines, which was not reported by other seismic imaging studies. This corridor of shallower Moho is located beneath the surface outcrop of the Permian magmatic rocks and seems to be connected to the continuation of the Permian magmatism to the deep-seated crust. We compared the shallow crustal velocities and the hypocentral location of the earthquakes in the Southern foothills of the Alps. It revealed that the seismicity mainly occurs in the S-wave velocity range between ∼3.1 and ∼3.6 km/s.

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“…In order to avoid interference of upper mantle tomography by crustal anomalies, Zhao et al (2016b) used the EPcrust reference model to correct for traveltime residuals within the crust (Molinari & Morelli, 2011). Although the EPcrust model does not include all the details of the most recent Moho maps (e.g., Lu et al, 2020;Spada et al, 2013), and the approach chosen by Zhao et al (2016b) does not include the effects of 3-D propagation of nonvertical rays from different azimuths in the heterogeneous crust (e.g., Waldhauser et al, 2002), synthetic tests performed by Zhao et al (2016b) indicate that their tomography model of V p perturbations is not significantly affected by smearing of crustal anomalies to mantle depth.…”

Section: Slab Structure From Teleseismic P-wave Tomographymentioning

confidence: 99%

“…(2016b) used the EPcrust reference model to correct for traveltime residuals within the crust (Molinari & Morelli, 2011). Although the EPcrust model does not include all the details of the most recent Moho maps (e.g., Lu et al., 2020; Spada et al., 2013), and the approach chosen by Zhao et al. (2016b) does not include the effects of 3‐D propagation of nonvertical rays from different azimuths in the heterogeneous crust (e.g., Waldhauser et al., 2002), synthetic tests performed by Zhao et al.…”

Section: Velocity Structure In the Upper Mantle Along The Cifalps Promentioning

confidence: 99%

The Deep Structure of the Alps Based on the CIFALPS Seismic Experiment: A Synthesis

Malusà

Guillot

Zhao

et al. 2021

Geochem Geophys Geosyst

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The European Alps are the site where classic geologic concepts such as nappe theory, continental subduction, and slab breakoff have been first proposed. However, the deep tectonic structure of the Alps has long been poorly constrained by independent geophysical evidence. This review paper summarizes the main results of the CIFALPS passive seismic experiment, which allows us to propose an updated image of the deep structure of the Alps at the scale of the lithosphere and the upper mantle. The concepts and ideas summarized in this article provide a baseline for further advances in the fields of Alpine tectonics and in the analysis of active continental margins more generally. MALUSÀ ET AL.

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Imaging Alpine crust using ambient noise wave-equation tomography

Cited by 43 publications

References 98 publications

Seismotectonics at the Transition Between Opposite‐Dipping Slabs (Western Alpine Region)

Seismotectonics at the Transition Between Opposite‐Dipping Slabs (Western Alpine Region)

High-Resolution Crustal S-wave Velocity Model and Moho Geometry Beneath the Southeastern Alps: New Insights From the SWATH-D Experiment

The Deep Structure of the Alps Based on the CIFALPS Seismic Experiment: A Synthesis

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