Higher-order cross-correlations (C3) to image the Earth from the crust to the core
Zack Spica
Stanford University
- Date & Time
- Location
- Building 3, Room 3240 (main USGS conference room)
- Host
- Valerie Sahakian
- Summary
The ambient noise correlation technique allows retrieving the Green's function between pairs of synchronous seismic sensors by correlating long time series of seismic noise (C1). While the method is widely used to map the seismic velocity in the crust and upper mantle with surface waves, recent works highlighted the possibility to retrieve teleseismic body waves, offering a better sampling geometries to image the Earth's core. However, the method relies on the availability of synchronous networks, which considerably limits the ray-paths coverage and therefore the resolution of the resulting tomographic images.
My point is to show that performing higher-order correlations (C3) makes it possible to bridge all the seismic networks in time and space, and therefore significantly enhance the resolving power of the ambient noise tomographies. I will discuss the feasibility and the potential of the method for Rayleigh waves retrieval, and present its first application to obtain a high-resolution tomographic image of Mexico and south US. In addition, I will show that the method can also be extended to retrieve teleseismic body waves such as reflections on the core mantle boundary (CMB). I will present a spatial analysis of the differential travel time of the ScS phase along the Meso America Subduction Experiment (MASE) array and discuss the strong influence of the shallow surface on such measurements.
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