Body-Wave Scattering from Seismic Interferometry: Preliminary Results from the San Andreas Fault near Parkfield, California

English Abstract:

High-resolution direct tomographic imaging of subsurface Earth structures is generally limited by the poor distribution of seismic sources necessary for such studies. However, seismic interferometry has the potential to significantly overcome this issue through the use of ambient seismic noise recordings. Whereas the recovery of virtual surface waves via seismic interferometry techniques are the most abundant results produced by such studies, it has recently been shown that virtual body waves can also be recovered under appropriate conditions. Of particular interest is the scattering of body waves produced by velocity discontinuities in the subsurface, which dramatically improve our ability to characterize the seismic velocity structure. In this work we investigate the possibility of recovering body-wave scattering from interactions with velocity discontinuities associated with the San Andreas Fault using ambient seismic noise recordings across a network of stations near Parkfield, California. In particular we test whether mode-conversions (P to S waves) can be observed using these virtual Green’s functions. Additionally, we examine the potential of seismic interferometry to produce time-lapse body-wave characterizations of the San Andreas Fault, in which properties of the fault can be seen to change in time.