Noise reduction and detection of weak, coherent signals through phase-weighted stacks |
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| Authors: | Martin Schimmel Hanneke Paulssen |
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| Institution: | Department of Theoretical Geophysics. Institute of Earth Sciences, Utrecht University, PO Box 80.021, 3508 TA Utrecht, the Netherlands. E-mail: schimmel@geof.ruu.nl |
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| Abstract: | We present a new tool for efficient incoherent noise reduction for array data employing complex trace analysis. An amplitude-unbiased coherency measure is designed based on the instantaneous phase, which is used to weight the samples of an ordinary, linear stack. The result is called the phase-weighted stack (PWS) and is cleaned from incoherent noise. PWS thus permits detection of weak but coherent arrivals. The method presented can easily be extended to phase-weighted cross-correlations or be applied in the τ p domain. We illustrate and discuss the advantages and disadvantages of PWS in comparison with other coherency measures and present examples. We further show that our non-linear stacking technique enables us to detect a weak lower-mantle P -to- S conversion from a depth of approximately 840 km on array data. Hints of an 840 km discontinuity have been reported; however, such a discontinuity is not yet established due to the lack of further evidence. |
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| Keywords: | array mantle discontinuities seismic noise time-series analysis |
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