Slab

About: Slab is a research topic. Over the lifetime, 31617 publications have been published within this topic receiving 318693 citations.

Tomography and thermal state of the Cocos plate subduction beneath Mexico City

Abstract: [1] The geometry and thermal state of the subducting Cocos plate beneath Mexico City has been enigmatic because of the absence of a deep Wadati-Benioff zone. We present a tomographic image of the slab based on inversion of 8869 teleseismic P wave travel times measured on a portable broadband seismic network. The images combined with receiver function analysis show that the slab runs flat from the coast to near Mexico City, where it dives into the mantle just before the Trans-Mexican Volcanic Belt with a dip of ∼75°. It continues down to a depth of ∼500 km at a distance of 400 km from the trench, where the tomography reveals that the dipping portion ends. As well as standard block tomography, we invert the travel time residuals for the parameters of a thermal slab model and find a slab thickness of 40 km that is consistent with the (15 Ma) age of the Cocos plate. The combination of a young hot plate and truncation at depth can explain the lack of deep seismicity due to high temperatures and lower negative buoyancy compared with an older, thicker, nontruncated plate.

Nonlinear waves guided by a dielectric slab

Abstract: We consider dispersion relations and field structure of TE-polarized guided waves travelling along an asymmetric dielectric slab surrounded by two different nonlinear media. For a given configuration there are four types of guided waves. Three of this four types possess at least one field maximum outside the slab region and have no counterpart in linear waveguide optics. The solutions of the dispersion relations depend now on an additional parameter making them more flexible with respect to the linear limit.

Active detachment faulting above the Peruvian flat slab

Abstract: The Cordillera Blanca detachment fault in the Peruvian Andes is, to our knowledge, the first active detachment to be documented above a modern flat slab. Crustal detachment has unroofed the ca. 8 Ma Cordillera Blanca batholith, now the backbone of the highest mountain range in Peru. Large-magnitude slip along the fault was thermally enhanced by emplacement of the batholith, the penultimate magmatic event prior to flattening of the Nazca slab. However, extensional models based on arc magmatism and crustal thickening alone do not adequately explain the scale or structural asymmetry of a series of young, deep-seated, west-dipping normal faults across Peru. Here we show that the onset of detachment faulting coincided with subduction of the aseismic Nazca Ridge and consequent flattening of the Nazca slab. We propose that slab buoyancy from ridge subduction triggered extensional collapse of the prethickened continental crust, and that this buoyancy drove footwall uplift that exceeds basin subsidence. The west-dipping asymmetry of late Cenozoic extensional faults in Peru may be controlled by a preexisting crustal anisotropy (older thrusts), and/or formation of Riedel-like shears kinematically linked to the flat Nazca slab.