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Arrival-angle anomalies across the USArray Transportable Array

Abstract:

We construct composite maps of surface-wave arrival-angle anomalies using clustered earthquakes and an array method for measuring wave-front geometry. This results in observations of arrival angles covering the entire footprint of the USArray Transportable Array during 2006-2010. Bands of arrival-angle deviations in the propagation direction indicate the presence of heterogeneous velocity structure both inside and outside of the array. We compare the observed patterns to arrival angles pbkp_redicted using two global tomographic models, the mantle model S362ANI and the surface-wave-dispersion model GDM52. We use both ray-theory-based pbkp_rediction methods and measurements on synthetic data calculated using a spectral-element method. Both models and all pbkp_rediction methods produce similar mean arrival angles and long-wavelength patterns of anomalies which are similar to the observations. Pbkp_redicted short-wavelength features generally do not agree with the observations. The spectral-element method produces some complexity that is not obtained using the ray-theory-based methods; this pbkp_redicted complexity is similar in character to the observed patterns, but does not match them.