Receiver Function Deconvolution with Noisy Seafloor Seismic Data: Imaging the Lithosphere of a Normal Ocean

Abstract:

The seismic structure of the normal oceanic lithosphere is pivotal to our understanding of global geodynamics and plate tectonics. However, the seafloor is a challenging environment for lithospheric imaging using source-deconvolution methods, e.g., Ps receiver functions. This is because at long periods, the earthquake signals may be obscured by tilt and compliance noise generated in the overlying ocean layer; additionally, at shorter periods, reverberations from the overlying water column or an underlying fluid-saturated sedimentary layer make inferences on deeper lithospheric layers difficult. In this study, we address this and other challenging factors that hamper signal detection from conversions generated at deeper lithospheric boundaries. We use earthquake records from the NoMelt experiment which is located on a mature (~70Ma) Pacific seafloor. We apply multiple techniques, including wave-field decomposition and spectral analysis, targeted at improving the earthquake signal detection necessary for further receiver function analysis. We obtain a total number of 688 high-quality records (SNR>2.0 on the vertical channel) from 16 stations. Receiver function quality is improved through beamforming across the entire NoMelt array. We suppress the sedimentary layer reverberations by applying a resonance removal filter. Preliminary results show that our analysis can successfully recover the Moho, giving a crustal thickness of 7.3 ± 0.8 km. We will test our approach on synthetic seismograms to further demonstrate their effectiveness. This is crucial for robust high-resolution body-wave imaging of the oceanic lithosphere across a growing number of seafloor seismic arrays. Future work will also investigate the lithosphere-asthenosphere transition and supplement long-wavelength surface wave studies necessary for testing models of oceanic plate origin and evolution.