Direct Detection of Sharp Upper-Mantle Structures Beneath the Western United States Using Waveform Complexity Analysis

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AmplitudeComplexity (DLR) Data-Synth (DT) • Many TA waveforms

exhibit significant complexity (ΔLR) that can be described by a multi-pathing effect•Larger ΔLR values = more complex waveform•Large ΔLR values are associated with low amplitudes. •Azimuthal dependence in ΔLR is observed, suggesting that the anomalies in the upper-mantle beneath western US mainly dip to the south.

[Sun and Helmberger, 2011, GJI]