Imaging the D" reflector with noise correlations and array processing

Abstract:

Seismic noise correlation is used nowadays to retrieve interstation body waves propagation at global scale. While the accuracy long period retrieved body waves are still under debate, short period (~7sec) P waves sampling the deep mantle can be used to infer the fine structure of the Earth. Thus accurately reconstructed body waves as PcP can be sued to study the structure in the vicinity of the core mantle boundary, and study the presence of low and high velocity layer above the CMB.

By using double beam forming we demonstrate that seismic noise correlations can be used to robustly image deep mantle reflections with a quality superior to that of earthquake data. The arrival time and slowness for noise and earthquakes sampling one region beneath Siberia are identical and the small amplitude reflections are sufficiently clear in the noise correlations to compare them reliably to synthetic data. Our study area is characterised by high seismic velocities and the imaged reflector at 2530 km depth is consistent with predictions for this scenario. Our results open exciting prospects of illuminating new target zones in the deep mantle to further constrain the dynamics and mineralogy of the deep Earth.