Seismic body-wave interferometry using noise autocorrelations for crustal structure

In this study, we use ambient seismic noise recorded at selected broad-band USArray Earth-scope Transportable Array (TA) stations to obtain effective reflection seismograms using noise autocorrelations. In order to best retrieve the body-wave component of the Green's function beneath a station from ambient seismic noise, a number of processing steps are used, including temporal sign-bit normalization, spectral whitening and bandpass filtering. Hourly autocorrelations are stacked for different time periods including one day, one month and one year. On the final stack, different amplitude gain functions are applied, including automatic gain control (AGC), to equalize the correlation amplitudes. The robustness of the resulting ambient noise autocorrelations is first tested on a TA station in Nevada where we are able to identify arrivals similar to those found in an earlier study. We then investigated noise autocorrelations applied to several USArray TA stations in the central U.S., and the results were then compared with reflectivity synthetics for an average crustal model based on CRUST 1.0 where an AGC was used to enhance the later arrivals. Different stacking periods are also investigated in order to find stable correlation stacks.