Structure of central and southern Mexico from velocity and attenuation tomography

Abstract

[1] The 3D V p , V p /V s , P-and S-wave attenuation structure of the Cocos subduction zone in Mexico is imaged using earthquakes recorded by two temporary seismic arrays and local stations. Direct P wave arrivals on vertical components and direct S wave arrivals on transverse components from local earthquakes are used for velocity imaging. Relative delay times for P and PKP phases from teleseismic events are also used to obtain a deeper velocity structure beneath the southern seismic array. Using a spectral-decay method, we calculate a path attenuation operator t* for each P and S waveform from local events, and then invert for 3D spatial variations in attenuation (Q p À1 and Q s À1 ). Inversion results reveal a low-attenuation and high-velocity Cocos slab. The slab dip angle increases from almost flat in central Mexico near Mexico City to about 30 in southern Mexico near the Isthmus of Tehuantepec. High attenuation and low velocity in the crust beneath the Trans-Mexico Volcanic Belt correlate with low resistivity, and are probably related to dehydration of the slab and melting processes. The most pronounced high-attenuation, low-V p and high-V p /V s anomaly is found in the crust beneath the Veracruz Basin. A high-velocity structure dipping into the mantle from the side of Gulf of Mexico coincides with a discontinuity from a receiver functions study, and provides an evidence for the collision between the Yucatán Block and Mexico in the Miocene.

Reassessing the 2006 Guerrero slow‐slip event, Mexico: Implications for large earthquakes in the Guerrero Gap

“…The Pacific Plate subducts beneath the North America plate about 66 km south‐southwest off the coastal city Acapulco with a dip angle of 15° and becomes subhorizontal at a depth of 40 km, approximately 80 km north‐northeast from Acapulco (Figure ). The interface remains horizontal until about 230–250 km from the coast, after which it dips steeply below the Trans‐Mexican Volcanic Belt, at an angle of 75° [ Kim et al , ; Chen and Clayton , ]. We use the same subduction geometry as Radiguet et al [] and Cavalie et al [] (red solid line in Figure ), which correlates with observations from receiver functions [ Kim et al , ] (green markers).…”

Crust and upper-mantle seismic anisotropy variations from the coast to inland in central and Southern Mexico

“…Pardo & Suárez (1995) mapped the change on the slab's dip angle using local earthquake locations. Recently, more precise estimations of this geometry were obtained using teleseismic converted phases (Pérez-Campos et al 2008;Kim et al 2010Kim et al , 2012Song & Kim 2012a,b) and seismic wave tomography (Husker & Davis 2009;Chen & Clayton 2012) using an array of 100 broad-band temporary stations known as the MesoAmerican Subduction Experiment (MASE). MASE crossed Mexico from Acapulco, Guerrero, at the Pacific coast, to Tempoal, * Now at: Seismological Laboratory, California Institute of Technology, Pasadena, CA 91125, USA.…”

Lateral heterogeneity imaged by small‐aperture ScS retrieval from the ambient seismic field

“…Among these are a localized ultralow velocity layer on the top of the slab [Song et al, 2009], a remnant of the Cocos slab at greater depth, truncation of the Cocos slab by the Yucatán slab [Chen and Clayton, 2012], and strong heterogeneity in the mantle wedge [Chen and Clayton, 2009]. Also, full 3-D simulations that include the vertical gradient of the velocity would help us model the observed data more accurately.…”