On the Limitations of Interstation Distances in Ambient Noise Tomography

Thursday, 18 December 2014
Yinhe Luo, China University of Geosciences Wuhan, Wuhan, China and Yingjie Yang, Macquarie University, ARC Centre of Excellence for Core to Crust Fluid Systems and GEMOC, Sydney, NSW, Australia
Ambient noise tomography (ANT) has recently become a popular tomography method to study crustal structures thanks to its unique capability to extract short-period surface waves. Empirically, in order to reliably measure surface wave dispersion curves from time-domain cross-correlations, interstation distances between a pair of stations have to be longer than two/three wavelengths. This requirement imposed a strong constraint on the use of ambient noise tomography at the long-period end at local- and regional-scale tomography studies. In this study, we use ambient noise data from USArray/Transportable Array recorded during 2007-2012 to investigate whether dispersion measurements from cross-correlations of ambient noise at short interstation distances are consistent with those at long distances and whether the short-path dispersion measurements can be used in tomography, especially in local- and regional-scale tomography. Our results show that: (1) surface wave phase velocity dispersion curves measured by a Frequency-Time Analysis technique (FTAN) from time-domain cross-correlations are consistent with those measured by a spectral method tracing the zero crossings of the real part of cross spectrum functions in frequency domain; (2) dispersion measurements from time-domain cross-correlations with short interstation distances, up to only one wavelength, are consistent with and also reliable as those with interstation distances longer than three wavelengths; and (3) these short-path measurements can be included in ambient noise tomography to improve path coverage and resolution. This work is supported by the National Science Foundation of China (NSFC, #41374059) and the Special Fund for Basic Scientific Research of Central Colleges, China University of Geosciences (Wuhan) (#CUG090106 and #CUGL100402).