Shallow crustal radial anisotropy beneath the Tehran basin of Iran from seismic ambient noise tomography

Shirzad, Taghi; Shomali, Zaher‐Hossein

doi:10.1016/j.pepi.2014.04.001

Cited by 30 publications

(16 citation statements)

References 41 publications

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“…This assumption is at odds with the radial anisotropy determined from noise correlations, which is generally negative in the shallow crust beneath the Alberta Basin (Figure 6a). Similar observations have been recently reported in the shallow deposits of the Tehran Basin and interpreted as resulting from vertical alignments of cracks (Shirzad & Shomali, 2014). We will defer a detailed discussion and interpretation of seismic anisotropy east of the CDF to a future study due to (1) the modest amplitude of this anomaly, which is far below the level observed in the Cordillera, and (2) the lack of the need for shear wave anisotropy based on a "squeezing test" (Figure 8).…”

Section: Journal Of Geophysical Research: Solid Earthsupporting

confidence: 89%

Shear Velocity and Radial Anisotropy beneath Southwestern Canada: Evidence for Crustal Extension and Thick‐Skinned Tectonics

Wang

Chen

2020

JGR Solid Earth

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Deformation‐associated craton assembly and Cordilleran orogenesis played major roles during the crustal formation beneath the western margin of North America. To improve the understanding of the deformation history in this region, we investigate the crustal shear velocity and anisotropy by analyzing fundamental mode Rayleigh and Love waves from ambient seismic noise. Continuous recordings from 118 regional broadband stations reveal lateral variations in both velocity and anisotropy with strong spatial affinities to major geological domains. Strong variations in radial anisotropy, which dips westward and extends to at least midcrustal depths, suggest a “thick‐skinned” foreland thrust‐and‐fold belt beneath the Canadian Rocky Mountains. Our regional data also suggest increased horizontal shear velocities beneath the southern Canadian Cordillera, particularly near the Omineca Belt, which may have resulted from strong zonal deformation within the Cordilleran crust. This anisotropic anomaly migrates southward, and its spatial extent agrees well with the normal fault distribution to the west of the Rocky Mountain Trench. Our observations offer new evidence for the Eocene extension of the orogenic hinterland during the trans‐tensional motion of the Cordillera to the North American craton.

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Section: Journal Of Geophysical Research: Solid Earthsupporting

confidence: 89%

Shear Velocity and Radial Anisotropy beneath Southwestern Canada: Evidence for Crustal Extension and Thick‐Skinned Tectonics

Wang

Chen

2020

JGR Solid Earth

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“…It is locally focused near the Bolivian Orocline, with less shortening of the overriding plate to the north and south of the CAP. There has been a concerted effort to understand the response of the midcrust and lower crust to large crustal thicknesses resulting from tectonic shortening (e.g., Beaumont et al, 2001Beaumont et al, , 2006Chen et al, 2016;Cheng et al, 2013;Guo et al, 2012;Guo et al, 2016;Huang et al, 2010;Ling et al, 2017;Luo et al, 2013;Moschetti et al, 2010;Ojo et al, 2017;Pawlak et al, 2012;Royden et al, 1997;Shapiro et al, 2004;Shirzad et al, 2017;Shirzad & Shomali, 2014;Xie et al, 2013). In the Andes, numerous studies have suggested north-south crustal flow away from the regions with highest estimated shortening, near the Bolivian Orocline, to regions with less shortening (Eichelberger et al, 2015;Gerbault et al, 2005;Hindle et al, 2005;Husson & Sempere, 2003;Kley & Monaldi, 1998;McQuarrie et al, 2005;Oncken et al, 2006;Ouimet & Cook, 2010;Schepers et al, 2017;Yang et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

Midcrustal Deformation in the Central Andes Constrained by Radial Anisotropy

et al. 2018

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The Central Andes are characterized by one of the largest orogenic plateaus worldwide. As a result, they are home to some of the thickest continental crust observed today (up to ~75‐km thick). Understanding the response of the crust to such overthickening provides insights into the ductile behavior of the midcrust and lower crust. One of the best tools for examining crustal‐scale features is ambient noise tomography, which takes advantage of the ambient noise wavefield to sample crustal depths in great detail. We extract Love and Rayleigh wave phase velocities from ambient noise data to invert for Vsh, Vsv, and radial anisotropy throughout the Central Andes. We capture detailed crustal structure, including pronounced along‐strike isotropic velocity heterogeneity and substantial (up to 10%) radial anisotropy that varies with depth. This crustal anisotropy may have several origins, but throughout the majority of the Central Andes, particularly beneath the Altiplano, we interpret radial anisotropy as the result of mineral alignment due to ductile crustal deformation. Only in the strongly volcanic Altiplano‐Puna Volcanic Complex is radial anisotropy likely caused by magmatic intrusions.

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“…With a dense recording array, both high-frequency surface waves Shirzad & Shomali 2014;Fang et al 2015) and body wave signals (Nakata et al 2015) can be extracted, and used to determine the structure. The ellipticity of the Rayleigh-wave particle motion is also being measured (Savage et al 2013) which can be used to infer the depth of the basin.…”

Section: Introductionmentioning

confidence: 99%

Higher-mode ambient-noise Rayleigh waves in sedimentary basins

Clayton

2016

Geophys. J. Int.

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S U M M A R YWe show that higher modes are an important component of high-frequency Rayleigh waves in the cross-correlations over sedimentary basins. The particle motions provide a good test for distinguishing and separating the fundamental from the first higher mode, with the fundamental mode having retrograde and the first higher mode having prograde motion in the 1-10 s period of interest. The basement depth controls the cut-off period of the first higher mode, which coincides with a rapid increase (over period) in the particle-motion ellipticity or H/V ratio of the fundamental mode. The strong higher mode we observed is not only due to the low-velocity sedimentary layer but also due to the noise sources with significant radial component such as the basin edge scattering. It is important to correctly identify the mode order when inverting the dispersion curves because misidentifying the higher mode as fundamental will lead to an anomalous high V SV velocity.

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Shallow crustal radial anisotropy beneath the Tehran basin of Iran from seismic ambient noise tomography

Cited by 30 publications

References 41 publications

Shear Velocity and Radial Anisotropy beneath Southwestern Canada: Evidence for Crustal Extension and Thick‐Skinned Tectonics

Shear Velocity and Radial Anisotropy beneath Southwestern Canada: Evidence for Crustal Extension and Thick‐Skinned Tectonics

Midcrustal Deformation in the Central Andes Constrained by Radial Anisotropy

Higher-mode ambient-noise Rayleigh waves in sedimentary basins

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