Crust and upper mantle shear wave structure of Northeast Algeria from Rayleigh wave dispersion analysis

Radi, Zohir; Yelles‐Chaouche, Abdelkrim; Corchete, V.; Guettouche, Salim

doi:10.1016/j.pepi.2017.06.013

Cited by 11 publications

(3 citation statements)

References 27 publications

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“…This heat flow is higher than observed in typical active fold and thrust belts around the world (Booth‐Rea et al., 2008; Lucazeau, 2019; Morgan & James, 1989). Furthermore, lithospheric thickness shows a strong decrease from values above 180 km south of the Tunisian South Atlassic thrust and values around 140 (Globig et al., 2016) and probably less under the Southern Atlas STEP boundary where negative shear wave velocity anomalies are observed around 80–100 km depth (Radi et al., 2017). This relative thin lithospheric thickness in Tunisia is also accompanied by abundant hydrotermalism in the region (Dhia, 1987), mantle degassing (Fourré et al., 2011) and related high‐temperature Fe‐Zn‐Pb mineralizations (>190°C) since the late Miocene (e.g., Ben Aïssa et al., 2018; Benchilla et al., 2003; Decrée et al., 2008; Jemmali et al., 2014).…”

Section: Discussionmentioning

confidence: 99%

Metamorphic Domes in Northern Tunisia: Exhuming the Roots of Nappe Belts by Widespread Post‐Subduction Delamination in the Western Mediterranean

et al. 2023

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Cenozoic extension in the Western Mediterranean has been related to the dynamics of back-arc domains. Although, in most of its orogenic belts extension propagated into the fore-arc nappe domains. Here we revisit the structure, metamorphism and radiometric ages of the Tunisian Tell, where HP/LT rocks (350°C at 0.8 GPa), were exhumed by the sequential activity of extensional detachments after heating and decompression (410°C-440°C at 0.6-0.3 GPa) in a plate convergent setting. Normal faults thinning the Tunisian Tell detached at two different crustal levels. The shallower one cuts down into the Atlas Mesozoic sequence, involving Tellian Triassic evaporites in the hanging-wall forming halokinetic structures in the Mejerda basin late Miocene. The deeper-detachment bounds metamorphic domes formed by marbles and metapsammites from the Atlas domain. Illite crystallinity on Triassic rocks shows epizonal to anchizonal values, at deep and intermediate structural depths of the Tell-Atlas nappe belt, respectively. New U-Pb 49.78 ± 1.28 Ma rutile ages from Tellian metabasites, together with existing phlogopite 23-17 Ma K-Ar ages in Atlas marbles from the footwall of the deepest detachment, indicate a polymetamorphic evolution. The Tell rocks underthrusted the Kabylian flysch in the early Eocene. Further, early Miocene shortening thrusted the metabasites over lower-grade sediments, producing HP/LT metamorphism and ductile stretching at the base of the Atlas belt. The exhumation of midcrustal roots of Western Mediterranean nappe belts after tectonic shortening is a common feature related to tearing at the edges of the subduction systems and inboard delamination of their subcontinental lithospheric mantle.Plain Language Summary Mountain belts are formed by shortened sedimentary rocks. The Tell cordillera in Northern Tunisia is interpreted as a classic mountain belt developed through protracted shortening from the late Cretaceous until Present, formed by folded and overthrusted rocks, and intruded by salt bodies. However, we show here that conversely, some of the supposed salt bodies are formed by metamorphic rocks that were originally buried at depths of approximately 26 km. Moreover, the remaining salt structures in the Tunisian Tell formed in relation to the late-stage thinning and collapse of the mountain belt, as they intrude through extensional faults into late Miocene sediments. We characterize the temperature and pressure conditions reached by the metamorphic rocks and obtain a 49 Ma age of an early metamorphic event by radiometric dating of rutile. Metamorphic rocks where also exhumed in other Western Mediterranean mountain belts like the Betics, Rif, Algerian Tell after the main shortening stage. We relate this process to delamination, a deep mantle tectonic mechanism, which strips the nappe belt crustal domain from its underlying mantle root.BOOTH REA ET AL.

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Section: Discussionmentioning

confidence: 99%

Metamorphic Domes in Northern Tunisia: Exhuming the Roots of Nappe Belts by Widespread Post‐Subduction Delamination in the Western Mediterranean

et al. 2023

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“…It's of strong energy, slow attenuation and high signal-to-noise ratio. Rayleigh wave based exploration methods identify structures by estimating shear wave velocity, which is now widely applied in engineering cite selection (Beaty et al, 2002), cavity detection (Kaslilar et al, 2013), low-speed identification (Bao et al, 2015), seismic location (Jia et al, 2017), and crustal and mantle structure analysis (Radi et al, 2017;Zhang et al, 2021). Rayleigh wave exploration consists of three key steps, namely data acquisition, dispersion curves extraction and inversion.…”

Section: Introductionmentioning

confidence: 99%

Inversion of Rayleigh Wave Dispersion Curves Via BP Neural Network and PSO

Luo

2023

Preprint

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Rayleigh wave is widely applied in engineering exploration and geotectonic research. While how to reconstruct the corresponding geological information via Rayleigh wave is the critical process and difficulty. This paper presents an inversion method of Rayleigh wave dispersion curves based on BP neural network and PSO. In this work, a sample set that referring to the actual stratum distribution is firstly generated. Then, BP neural network is adopted to train the nonlinear mapping relationship between the dispersion curves and the shear wave velocity of each stratum. The trained BP neural network can quickly output a predicted value with rationality but poor precision, which can be utilized as the initial model of PSO inversion. PSO will then be adopted to further optimize the inversion result on the basis of BP neural network prediction. The combination of BP neural network and PSO aims at overcoming the defects of BP neural network that unable to carry out continual optimization and the slow optimization of PSO in the absence of reasonable initial solution. Finally, the effectiveness of the proposed algorithm is verified by a series of synthetic models and an active-source Rayleigh wave experiment carried out in a new railway project from Baotou, Inner Mongolia to Yinchuan, Ningxia.

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“…Como as ondas Rayleigh e Love são sensíveisàs variações de velocidade no manto superior, ao medirmos a velocidade com a qual essas ondas se propagam, podemos obter informações sobre as variações de propriedades físicas da litosfera. As velocidades são determinadas a partir da análise dos registros feitos por estações para diferentes fontes sísmicas (Radi et al, 2017).…”

Section: Ondas De Superfície Dispersão E Modos Normaisunclassified

Modelo de velocidade da onda S (1D) para a litosfera da Bacia do Pantanal

Tadeu¹

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The Pantanal Sedimentary Basin is seismically active, with recorded earthquakes of magnitudes up to m b 5.4. The upper mantle of this region exhibits a relatively low P and S seismic wave velocity, compared to neighboring regions in South America (Assumpção et al., 2004) (Feng et al., 2007. To better understand the cause of this velocity anomaly in the Pantanal Basin, we analyzed surface wave dispersion curves of earthquakes with magnitudes greater than or equal to 5.5, with different azimuthal distributions. We measure phase and group velocities for the fundamental and first superior vibration modes for Rayleigh surface waves and the fundamental mode of Love wave dispersion curves. We apply the Multiple Filtering Technique and stacking methods to obtain the group and phase velocities of the Rayleigh and Love waves. This allowed us to obtain S wave velocity (1D) models for the Pantanal Basin. The group and phase velocities were inverted using the linear method of Surf96, resulting in six S-wave velocity models for the Pantanal Basin.Two models exhibit velocities higher than those in IASP91 at 110 km and 150 km depth.The other four have low-velocities in a region between 110 km and 120 km, as well as at 150 km depth. This most likely evidences a thinner lithosphere in the Pantanal Basin, as proposed by Assumpção et al. (2004).

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Crust and upper mantle shear wave structure of Northeast Algeria from Rayleigh wave dispersion analysis

Cited by 11 publications

References 27 publications

Metamorphic Domes in Northern Tunisia: Exhuming the Roots of Nappe Belts by Widespread Post‐Subduction Delamination in the Western Mediterranean

Metamorphic Domes in Northern Tunisia: Exhuming the Roots of Nappe Belts by Widespread Post‐Subduction Delamination in the Western Mediterranean

Inversion of Rayleigh Wave Dispersion Curves Via BP Neural Network and PSO

Modelo de velocidade da onda S (1D) para a litosfera da Bacia do Pantanal

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