A dipping, thick segment of the Farallon Slab beneath Central US
نویسندگان
چکیده
It has been hypothesized that much of the crustal deformation attributed to the Laramide orogeny of the southwest North American Cordillera was caused by dynamic effects induced by the flat subduction of a large oceanic plateau that was embedded within the Farallon plate. Previous studies have identified within the North American mantle a seismic velocity anomaly that plausibly represents the remnants of the subducted plateau. Coupled plate kinematic and dynamic modeling of the anomaly, as well as surface geological findings identify this anomaly as the subducted conjugate to the Shatsky Rise. Here, we find clear evidence for a northeastward dipping (35° dip), thick (up to 400 km thick) slab-like seismic velocity anomaly within the top of the lower mantle below the central United States. Using a deep focus earthquake below Spain, we find that the observed seismic waveforms recorded with the dense USArray display multi-pathing indicative of sharp surfaces. Plate tectonic
منابع مشابه
Reconstructing Farallon plate subduction beneath North America back to the Late Cretaceous.
Using an inverse mantle convection model that assimilates seismic structure and plate motions, we reconstruct Farallon plate subduction back to 100 million years ago. Models consistent with stratigraphy constrain the depth dependence of mantle viscosity and buoyancy, requiring that the Farallon slab was flat lying in the Late Cretaceous, consistent with geological reconstructions. The simulatio...
متن کاملDistribution of hydrous minerals in the subduction system beneath Mexico
Teleseismic converted phases are used to probe the composition of the downgoing oceanic crust as a function of depth along the Cocos slab in central and southern Mexico. Previously, modeling of the receiver function (RF) conversion amplitude of the flat Cocos slab beneath central Mexico at 45 km depth revealed a thin low-velocity upper oceanic crust of a thickness of 471 km, which has much lowe...
متن کاملDescent of the ancient Farallon slab drives localized mantle flow below the New Madrid seismic zone
[1] The great earthquake sequence that occurred in the central Mississippi River Valley during the winter of 1811– 1812 is unprecedented in the historical record of seismicity within stable continental plate interiors. We show, using viscous flow models based on high resolution seismic tomography, that the descent of the ancient Farallon slab into the deep mantle beneath central North America i...
متن کاملComplex anisotropy beneath the Peruvian flat slab from frequency- dependent, multiple-phase shear wave splitting analysis
[1] Flat or shallow subduction is a relatively widespread global occurrence, but the dynamics remain poorly understood. In particular, the interaction between flat slabs and the surrounding mantle flow has yet to be studied in detail. Here we present measurements of seismic anisotropy to investigate mantle flow beneath the Peruvian flat-slab segment, the largest present-day region of flat subdu...
متن کاملFossil slabs attached to unsubducted fragments of the Farallon plate.
As the Pacific-Farallon spreading center approached North America, the Farallon plate fragmented into a number of small plates. Some of the microplate fragments ceased subducting before the spreading center reached the trench. Most tectonic models have assumed that the subducting oceanic slab detached from these microplates close to the trench, but recent seismic tomography studies have reveale...
متن کامل