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Abstract:
Traditional seismology often assumes that seismic waves travel through the mantle within the great circle path, in the sagittal plane along sources and receivers. Since the 1990s it was already known that subducted oceanic lithosphere in the mantle could laterally deviate the path of seismic signals, which arrive with different angles (out-of-plane) at an array of sensors at teleseismic distances. Detecting these signals with array processing techniques, and the consequent back-projection, have provided valuable information on the location of both ancient and actual subducted slabs. This hypothesis was also tested with synthetic seismograms by a study which carried out a preliminary modelling of P-to-P out-of-plane signals, providing hints on “how and where to look”. In this work, we conduct 3D waveform modelling to assess to which extent these out-of-plane signals can be used to infer physical properties of the slabs (e.g., thickness, age, orientation, velocity, and density contrasts). An important aspect to investigate is how these slabs affect the waveforms of both P and S out-of-plane signals, and if these signals are influenced by the presence of oceanic crust. Conversions P-to-S and S-to-P could provide additional constraints. Although still at the initial stage, the experiment shown here provides already useful information for more complex and realistic setting which will be tested in the future.Furthermore, LLSVPs will be tested as cause for deep mantle out-of-plane signals generated from their boundaries.
