Preprints
https://doi.org/10.5194/se-2020-189
https://doi.org/10.5194/se-2020-189

  10 Dec 2020

10 Dec 2020

Review status: a revised version of this preprint was accepted for the journal SE and is expected to appear here in due course.

Teleseismic P-waves at the AlpArray seismic network: Wave fronts, absolute traveltimes and traveltime residuals

Marcel Heinz Paffrath1, Wolfgang Friederich1, and the AlpArray and AlpArray-Swath D working group Marcel Heinz Paffrath et al.
  • 1Ruhr-Universität Bochum
  • Full list of participants at the end of the paper.

Abstract. We present an extensive dataset of highly accurate absolute traveltimes and traveltime residuals of teleseismic P- waves recorded by the AlpArray Seismic Network and complementary field experiments in the years from 2015 to 2019. The dataset is intended to serve as the basis for teleseismic delay time tomography of the upper mantle below the greater Alpine region. In addition, the data may be used as constraints in full-waveform inversion of AlpArray recordings. The dataset comprises about 170.000 onsets derived from records filtered to 0.5 Hz and 214.000 onsets from records filtered to 0.1 Hz. The high accuracy of absolute and residual traveltimes was obtained by applying a specially designed combination of automatic picking, waveform cross-correlation and beam-forming. Taking traveltime data for individual events, we are able to visualize in detail the wavefronts of teleseismic P-waves as they propagate across AlpArray. Variations of distances between isochrons indicate structural perturbations in the mantle below. Traveltime residuals for individual events exhibit spatially coherent patterns that prove to be reproducible if events of similar epicentral distance and azimuth are considered. When residuals for all available events are stacked, conspicuous areas of negative residuals emerge that already indicate the lateral location of subducting slabs beneath the Apennines and the western, central and eastern Alps. Stacking residuals for events from 90 degree wide azimuthal sectors results in lateral distributions of negative and positive residuals that are generally consistent but differ in detail due to the differing direction of illumination of mantle structures by the incident P-waves. Comparing traveltimes from the 0.5 Hz and the 0.1 Hz dataset, we observe on average earlier arrivals in the 0.5 Hz dataset presumably caused by velocity dispersion. Uncertainties of traveltime residuals are estimated from the peak width of the cross-correlation function and its maximum value. The median uncertainty is 0.15 s at 0.5 Hz and 0.18 s at 0.1 Hz, way below the typical traveltime residuals of up to ±2 s. Uncertainties display a regional dependence caused by quality differences between temporary and permanent stations as well as location dependent noise conditions.

Marcel Heinz Paffrath et al.

 
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Marcel Heinz Paffrath et al.

Marcel Heinz Paffrath et al.

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Short summary
Using the AlpArray seismic network, we have determined highly accurate arrival times of P-waves from over 350 major global earthquakes between 2015 and 2019, which shall be used for a tomography of the mantle beneath the greater Alpine region. Comparing with theoretical traveltimes of a standard reference earth model, we receive very stable patterns of arrival time differences across the network which provide evidence of varying subduction behaviour along the strike of the Alpine orogen.