Subducted Lithosphere Under South America From Multifrequency P Wave Tomography

Abstract

Global-scale teleseismic P-wave tomography model DETOX-P1 is analyzed under South America.• The shallowest and the deepest slabs are found under (north)west South America, while intermediate-depth slabs are found farther east.• If slabs sank roughly vertically, they initially formed under intra-oceanic trenches, up until Late Cretaceous times.

The effect of a weak asthenospheric layer on surface kinematics, subduction dynamics and slab morphology in the lower mantle

“…The opposite would be expected if slabs retained a constant thickness across depths. Hence the deeper slab must be thicker Ribe et al (2007); Loiselet et al (2010), which is well-documented under the Americas Karason & Van Der Hilst (2000); Ren et al (2007); Sigloch & Mihalynuk (2013);Mohammadzaheri et al (2021), but also globally Van der Voo et al (1999); Shephard et al (2017); Van der Meer et al (2018); Hosseini et al (2020). Under the particularly well-instrumented Cascadia subduction zone of North America, tomography can resolve a shallow slab of single lithospheric thickness, and also confidently show that the slab is multiply thickened from the transition zone downward Sigloch et al (2008).…”

Regional Geophysics of the Caribbean and Northern South America: Implications for Tectonics

“…However, in model UU-P07, the Caribbean slab flattens at the 660-discontinuity, whereas this flattening is not evident in the DETOX-P1 model (Figure 13a). The positions of the Cocos and Farallon slabs (Figure 13a) are highly A comparison of the DETOX-P1 tomography model (Hosseini et al, 2020;Mohammadzaheri et al, 2021) with the recent S-wave tomographic models of Zhu et al (2020) and Celli et al (2020) shows: (a) excellent agreement for the geometry and depth extent of the high-velocity subducting slabs and (b) poor agreement for the strength of the low-velocity features beneath the Caribbean plate.…”

“…Deformation of the southern tip of the Aves ridge, the Lesser Antilles and the Leeward Antilles (Figure 16b; GAC; Kroehler et al, 2011;Vence & Mann, 2020) and portions of the oceanic plateau in the offshore of Venezuela 2010) present a range of two-dimensional subduction zone thermal models showing that older slabs have a much colder thermal structure that is consistent with deeper (660 km) seismicity as the brittle-ductile transition persists to a greater depth. Seismic tomography models (Mohammadzaheri et al, 2021) show that the subducting slabs in the circum-Caribbean extend into the lower mantle, below the bottom of the mantle transition zone at 660 km depth. However, as shown in Figure 17, seismicity does not reach depths greater than 200 km, whereas the tomography Cross-sections A-Aʹ, B-Bʹ, and D-Dʹ display that the slabs go deeper than this.…”

Adjoint Waveform Tomography of South America

“…The slab geometry presented by Hayes et al (2018; Figure 2) interpolated earthquake gaps by using seismic-tomographic models. However, some tomographic models suggest gaps in the subducting Nazca Slab, such as downdip from the Peruvian Flat Slab (e.g., Mohammadzaheri et al, 2021).…”

“…In the Andes, continental-scale teleseismic P-and S-wave tomographic models (e.g., Portner et al, 2020;Rodríguez et al, 2021) have mapped the geometry of the subducting Nazca Slab below the Andes. However, some structural features are still controversial, such as the continuity of the slab at depths beyond the stagnant segment near the Peruvian Andes (Mohammadzaheri et al, 2021), or the geometry of the slab in the mantle transition zone. Beneath the AC (north of ∼20°S) global tomography models (Hosseini et al, 2020;Lei et al, 2020;Obayashi et al, 2013;Simmons et al, 2012) as well as continental models (Portner et al, 2020;Rodríguez et al, 2021) tend to show the Nazca Slab plunging directly into the lower mantle.…”