Crust-mantle boundary reflectors in Nevada from ambient seismic noise autocorrelations

Abstract

The depth of reflector layers in the Earth′s crust is usually estimated using controlled sources or earthquake signals. Ambient seismic noise, however, can also be used for this purpose. We develop and apply a new method, based on continuous waveform analysis, to estimate the two-way P-wave reflection component of the Green′s function beneath each station. The Green′s functions are retrieved from continuous record autocorrelation stacks at broad-band sensor locations within the USArray EarthScope Transportable Array in the western Great Basin and the Sierra Nevada, in a region with complex crustal and upper-mantle structure. In this paper, we show evidence of a reflector at the crust-mantle boundary (Moho discontinuity) derived for the first time from ambient noise autocorrelations using short-period (~1 s) data. Our results compare well with earthquake and controlled source investigations, and with tomography findings in the region. Moho depth is difficult to resolve seismically because of the lack of favourable spatial distribution of source and receiver geometries. In contrast, our method can be applied at any desired sensor spacing to estimate Earth reflector depth beneath surface-located sensors, providing unprecedented resolution.