The Origin of the Low‐Velocity Anomalies Beneath the Rootless Atlas Mountains: Insights Gained From Modeling of Anisotropy Developed by the Travel of Canary Plume

Abstract

Since Wilson (1963) suggested the existence of mantle plumes to explain the Hawaiian island chain, the vertical rise of buoyant material from the deep mantle and consequent decompression melting near the surface have been considered a mechanism for the formation of hotspots (e.g., Morgan, 1971;Sleep, 1990). The buoyancy of the hot mantle primarily originates from temperature. Therefore, there have been many attempts to better constrain the mantle plume structure using seismic tomography as the high-temperature mantle is imaged as low-seismic-velocity anomalies (e.g.

The Role of Subslab Low‐Velocity Anomalies Beneath the Nazca Ridge and Iquique Ridge on the Nazca Plate and Their Possible Contribution to the Subduction Angle

“…(2016) and Lee et al. (2021, 2022). Unaccounted‐for anisotropy can produce artificial velocity anomalies in isotropic tomography that can be misleading (Bezada et al., 2016; Blackman & Kendall, 1997; Eberhart‐Phillips & Henderson, 2004; Ishise & Oda, 2005; Lee et al., 2021; Lloyd & Van der Lee, 2008; Menke, 2015; Sobolev et al., 1999; VanderBeek & Faccenda, 2021).…”

“…In contrast, we find a velocity reduction of ∼1.5% dV P /V P in the SSLAs beneath the Iquique Ridge compared to the isotropic tomography (Figure 2). When the prescribed anisotropy in the inversion is not a good approximation of true mantle anisotropy, it may introduce additional artificial velocity structure and therefore lead to an increase in the model norm (Figure S9 in Supporting Information S1) (Bezada et al, 2016;Lee et al, 2021Lee et al, , 2022.…”

“…The hypothetical anisotropy field was derived from SWS observations (Deng et al, 2017;Eakin et al, 2014Eakin et al, , 2015Long et al, 2016;Lynner & Beck, 2020;Polet et al, 2000;Reiss et al, 2018) and it is constant throughout each iteration. Further details about our alternative method can be found in Bezada et al (2016) and Lee et al (2021Lee et al ( , 2022. Unaccounted-for anisotropy can produce artificial velocity anomalies in isotropic tomography that can be misleading (Bezada et al, 2016;Blackman & Kendall, 1997;Eberhart-Phillips & Henderson, 2004;Ishise & Oda, 2005;Lee et al, 2021;Lloyd & Van der Lee, 2008;Menke, 2015;Sobolev et al, 1999;VanderBeek & Faccenda, 2021).…”

“…Anisotropy measured by shear wave splitting (SWS) (Deng et al, 2017;Eakin et al, 2014Eakin et al, , 2015Long et al, 2016;Lynner & Beck, 2020;Polet et al, 2000;Reiss et al, 2018) has shown evidence for subduction segments with contrasting mantle geodynamics below two different ridge systems. Good coverage of SWS observation from dense seismic arrays in South America, where the Nazca and Iquique ridges subduct (Figure 1b), allows us to improve the quality of teleseismic tomography by incorporating anisotropy and thus to clarify mantle geodynamic processes (e.g., Bezada et al, 2016;Huang et al, 2019;Lee et al, 2021Lee et al, , 2022Wang & Zhao, 2012;Zhao et al, 2016). In particular, we can investigate whether SSLAs on isotropic velocity models can be explained by anisotropic structure.…”

The 2023 Mw 6.8 Morocco Earthquake: A Lower Crust Event Triggered by Mantle Upwelling?

“…Furthermore, the high-angle faulting on the TNT fault, as revealed by our inversion from the earthquake, indicates a deep-reaching offset to Moho and the top of upper mantle. Lee et al (2022) incorporated anisotropy as an a priori constraint in teleseismic P-wave travel-time tomography as mantle flow can develop seismic anisotropy. Their improved results are more consistent with the hypothesis that the low-velocity anomalies come from the mantle material of the Canary Plume.…”