Ambient noise tomography across the Central Andes

Abstract

The Central Andes of southern Peru, Bolivia, Argentina and Chile (between 12 • S and 42 • S) comprise the largest orogenic plateau in the world associated with abundant arc volcanism, the Central Andean Plateau, as well as multiple segments of flat-slab subduction making this part of the Earth a unique place to study various aspects of active plate tectonics. The goal of this continental-scale ambient noise tomography study is to incorporate broad-band seismic data from 20 seismic networks deployed incrementally in the Central Andes from 1994 May to 2012 August, to image the vertically polarized shear wave velocity (V sv) structure of the South American Cordillera. Using dispersion measurements calculated from the cross-correlation of 330 broad-band seismic stations, we construct Rayleigh wave phase velocity maps in the period range of 8-40 s and invert these for the shear wave velocity (V sv) structure of the Andean crust. We provide a dispersion misfit map as well as uncertainty envelopes for our V sv model and observe striking first-order correlations with our shallow results (∼5 km) and the morphotectonic provinces as well as subtler geological features indicating our results are robust. Our results reveal for the first time the full extent of the mid-crustal Andean lowvelocity zone that we tentatively interpret as the signature of a very large volume Neogene batholith. This study demonstrates the efficacy of integrating seismic data from numerous regional broad-band seismic networks to approximate the high-resolution coverage previously only available though larger networks such as the EarthScope USArray Transportable Array in the United States.

Crust and Lithospheric Structure - Global Crustal Structure

“…This method is advantageous for data from temporary seismic networks because it does not rely on the recording of teleseismic events, which may not occur during the operation of the temporary network. The method has seen widespread application (e.g., Shapiro et al, 2005;Ward et al, 2013).…”

Seismic structure in southern Peru: evidence for a smooth contortion between flat and normal subduction of the Nazca Plate

“…The goal of this experiment was to image the structure of the Peruvian subduction zone in the flat slab, transitional and normal dipping regions. The CAUGHT array consisted of 50 broad-band seismic instruments deployed from 2010 November to 2012 August in a 2-D geometry in the Central Andes of northern Bolivia and southern Peru (Ward et al 2013). Two stations of this array that are located within the interior of the box defined by the PeruSE array (Fig.…”

“…Receiver functions along this array suggest a continuous slab with no clear breaks (Phillips & Clayton 2014). In order to test this conclusion and expand on investigations of this region with additional data and analyses, we use regional earthquakes recorded by the Peru Subduction Experiment (PeruSE; PeruSE 2013) and Central Andes Uplift and Geodynamics of High Topography (CAUGHT; Ward et al 2013) seismic arrays to study the fine-scale structure of the southern Peru subduction zone along the flat-to-normal transition (Fig. 1).…”

Site effect determination using seismic noise from Tungurahua volcano (Ecuador): implications for seismo-acoustic analysis

“…Applications using noise information include tomography studies (e.g. Shapiro et al 2005;Ritzwoller et al 2011;Ward et al 2013), detection of stress changes in fault zones (Wegler & Schönfelder 2007), and volcano monitoring (Clarke et al 2013) (see Prieto et al 2011, for other applications). Such noise has been used to compute the site effects in Arenal (Mora et al 2001) and Vesuvius (Nardone & Maresca 2011) volcanoes, with the H/V method proposed by Nakamura (1989) which interprets the spectral ratios of horizontal to vertical components as amplitudes of the frequency response functions (FRF) of layered media.…”