Non-linear Waveform and Delay Time Analysis of Triplicated Core Phases

Non-linear Waveform and Delay Time Analysis of Triplicated Core Phases: A New Method to Extract Differential Travel Times From Interfering Data
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A new method to measure differential travel times and attenuation of seismic body waves has been developed. The problem is formulated as a non-linear inverse problem which is solved by simulated annealing inversion. Following examples demonstrate the potential of the technique, which is able to determine differential traveltimes and waveforms of the core phases, even when they interfere on the seismograms or when additional depth phases are present. This method has been applied to IRIS data in order to recover the structure of the Earth’s core. The main interest for such studies is the increase of the data coverage by adding shallow earthquake data usually rejected due to the interference between the direct and depth phases.
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Examples of data fit for a shallow earthquake (on the left) and a deep earthquake (on the right). The IRIS data are aligned on the PKPbc core phase arrival, the PKPdf and PKPab core phases are seen respectively before and after this arrival. For the shallow events, the depth phases are interfering with the direct core phases, but the processing allows to resolve this interference.
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Garcia R., S. Chevrot and M. Weber , 2004 Non linear waveform and delay time analysis of triplicated core phases, J. Geophys. Res., 109, B01306, DOI: 10.1029/2003JB002429

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