Mantle Tomography of Central‐Eastern USA: Influence of Inversion Volume Size

Abstract

The central and eastern United States (CEUS), inherited from Laurentia, has a thick, stable, and old continental lithosphere. The continental lithosphere, that is, the North American Craton (NAC), has remained stable for over 1.3 Ga despite subsequent reworking and deformation with the assembly and breakup of the Rodina and Pangaea supercontinents. In the past decade, seismic velocity structure of the crust and lithospheric mantle beneath the North American continent has been investigated by several techniques, including body wave tomography (

Seismic Anisotropy Tomography and Mantle Dynamics of Central‐Eastern USA

“…Figures 4–6 show the obtained 3‐D V p AAN model. The isotropic V p image obtained by the AAN tomography is almost the same as the V p model obtained by the isotropic inversion (see Figures 8 and 9 in Liang, Zhao, Hua, & Xu, 2022). In the crust and upper lithosphere (10–50 km depths; Figure 4), strong anisotropy occurs in the Appalachians Mountains and the Ouachita Mountains, which consist chiefly of folded and faulted sedimentary belts.…”

“…The ETSZ is developed from the suture zone between the Laurentia and Grenville basements. As discussed by Liang, Zhao, Hua, and Xu (2022), the low‐V anomaly beneath the ETSZ is more sensitive to teleseismic rays with a large ray spread angle from the SE direction. The existence of this low‐V anomaly is also confirmed by our synthetic tests (Figure 12) despite its smaller size and shallower depth than the NMSZ.…”

“…In the mantle transition zone (MTZ, 410–660 km depths), two high‐V anomalies are visible beneath the Great Plains and Central Lowland (H1 and H2 in Figures 5 and 6), but they are less clear as compared with those in the V p model obtained by the isotropic inversion (Figures 8 and 9 in Liang, Zhao, Hua, & Xu, 2022). This is because the FVDs in H1 and H2 are orientated nearly NW–SE at 300–400 km depths, which are mapped into the high‐V anomalies by the isotropic inversion due to the teleseismic rays from the NW direction (Figure S1 in Supporting Information S1).…”

“…For the teleseismic data, most events were recorded at over 100 stations in the CEUS, and crustal correction is made to remove the effect of crustal heterogeneities on relative residuals (Wang et al., 2019). Because the lateral extent of our study volume is very large (∼35°) and the teleseismic rays to the study volume exhibit a wide range of epicentral distance and incident angle, the contamination of the whole‐mantle heterogeneity to the relative residuals cannot be neglected (Liang, Zhao, Hua, & Xu, 2022). Therefore, we adopt a global V p tomographic model (Zhao et al., 2013) to make the whole‐mantle correction to the relative residuals so as to remove the influence of whole‐mantle heterogeneity on the regional teleseismic tomography (Liang, Zhao, Hua, & Xu, 2022).…”

“…Because the lateral extent of our study volume is very large (∼35°) and the teleseismic rays to the study volume exhibit a wide range of epicentral distance and incident angle, the contamination of the whole‐mantle heterogeneity to the relative residuals cannot be neglected (Liang, Zhao, Hua, & Xu, 2022). Therefore, we adopt a global V p tomographic model (Zhao et al., 2013) to make the whole‐mantle correction to the relative residuals so as to remove the influence of whole‐mantle heterogeneity on the regional teleseismic tomography (Liang, Zhao, Hua, & Xu, 2022). This approach improves the regional tomographic images beneath the CEUS effectively, especially in the deep mantle and edge parts of the study volume.…”