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Map showing the location of the Isthmus of Tehuantepec and various tectonic elements. Inset at bottom left shows stations of the Veracruz- Oaxaca (VEOX) array. 

Map showing the location of the Isthmus of Tehuantepec and various tectonic elements. Inset at bottom left shows stations of the Veracruz- Oaxaca (VEOX) array. 

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Article
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Shear-wave splitting measurements were made using S waves from local earthquakes recorded by stations of the Veracruz-Oaxaca array, which was deployed across the Isthmus of Tehuantepec. In this segment of the Middle America Trench, the oceanic Cocos Plate subducts under the continental North American Plate. Intraplate earthquakes within the Cocos s...

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Context 1
... the Gulf of California ( Obrebski et al. 2006;van Benthem et al. 2008;Long 2010), and on subduction of the Rivera and Cocos plates at the Middle America Trench (MAT) (van Benthem 2005;Stubailo & Davis 2007, 2012aSoto et al. 2009;Ponce-Cortés 2012;Rojo-Garibaldi 2012;van Benthem et al. 2013). These results are summarized for central Mexico in Fig. S1. The only work involving local S-wave splitting was conducted by Soto et al. (2009) for the Rivera and westernmost Cocos Plate, but given the limited depth extent of the slab seismicity they could only resolve the continental crust. In the present study, we report shear-wave splitting measurements from slab events in the Isth- mus of ...
Context 2
... Isthmus of Tehuantepec is the narrowest continental re- gion in southern Mexico and joins the Gulf of Mexico with the Pacific Ocean (Fig. 1). The Cocos Plate subducts beneath the North American continent and shows a change in geometry across the Isthmus of Tehuantepec. Farther west, under Guerrero state, the Cocos Plate subducts subhorizontally (Pardo & Suárez 1995;PérezCampos et al. 2008;Husker & Davis 2009;Kim et al. 2010). By the time it reaches the Isthmus of ...
Context 3
... dips at an angle of ∼25 • (Pardo & Suárez 1995; Rodríguez-Pérez 2007;Kim et al. 2011;Melgar & Pérez-Campos 2011). Farther east, under Chiapas state, the Cocos slab dips at an angle of 45 • ( Bravo et al. 2004;Rodríguez-Pérez 2007). Located offshore, the Tehuantepec Ridge (TR) subducts beneath the North American Plate at the Isthmus of Tehuantepec (Fig. 1). The age of the oceanic lithosphere presents a sudden change across the TR estimated at 7 Myr ( Manea et al. 2005) where the ridge intersects the MAT. The convergence velocity between the Cocos and North American plates at the intersection of the TR with the MAT is 7.2 cm yr −1 (DeMets et al. 2010), whereas the trench is retreating at ...
Context 4
... subducting plates reaching a depth of ∼110 km and the location of volcanic arcs has long been recognized (e.g. Tatsumi & Eggins 1995;Syracuse & Abers 2006). The main, modern volcanic feature in central and southern Mexico is the Trans- Mexican Volcanic Belt (TMVB), but it is located northwest of the area encompassed by the present study (e.g. fig. 1 in Manea & Manea 2006). It is related to the subhorizontal subduction of the Cocos Plate taking place to the west. Volcanic activity is found again in the Los Tuxtlas Volcanic Field (LTVF) near the coast of the Gulf of Mexico. The LTVF is located southeast from the TMVB and around the northernmost end of the array used in the present ...
Context 5
... data set used in this study was recorded by the Veracruz-Oaxaca (VEOX) experiment which was a dense linear array of 46 broad- band seismometers deployed along a N-S profile across the Isthmus of Tehuantepec (Melgar & Pérez-Campos 2011); see Fig. 1. The array operated from 2007 June to 2009 ...
Context 6
... studies have been conducted to determine the anisotropy in other segments of the MAT using local S waves from hypocentres within the slab. In Mexico, in a region located west of the present study (Fig. S1), the MApping the Rivera Subduction zone (MARS) array was deployed over the subducted Rivera and westernmost Cocos plates (Soto et al. 2009). Only events in the depth range from 60 to 106 km were used because seismicity does not extend any deeper. Soto et al. (2009) obtained a mean delay time of ∼0.2 s and inferred that the anisotropy ...
Context 7
... Supporting Information may be found in the online version of this article: Figure S1. Compilation of SKS measurements in central Mexico. ...

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... In the overriding plate the main source of . Shear wave splitting measurements averaged over a grid from local intraslab earthquakes deeper than 50 km red, are shown as thick short lines as reported in León Soto & Valenzuela (2013). Source side splitting results (Lynner & Long 2014a) are plotted at their surface projection of the source and presented with thick, green bars labelled by 1, 2 and 3. Anisotropic parameters for measurement labelled as 1 are (φ = 64.9 ...
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