%0 Journal Article %1 thorwart_dahm:2005 %A Thorwart, M. %A Dahm, T. %C Institut fr Geowissenschaften, Christian-Albrechts-Universitt zu Kiel, 24118 Kiel, Germany. E-mail: thorwart@geophysik.uni-kiel.de; Institut fr Geophysik, Universitt Hamburg, 20146 Hamburg, Germany %D 2005 %I Blackwell Publishing %J Geophysical Journal International %K geophysics seismology %N 2 %P 611--621 %R 10.1111/j.1365-246X.2005.02761.x %T Wavefield decomposition for passive ocean bottom seismological data %U http://dx.doi.org/10.1111/j.1365-246X.2005.02761.x %V 163 %X Seismic data from ocean bottom stations show strong water-layer multiples on the hydrophone and seismometer channels depending on the water depth and the seafloor impedance contrast. These multiples can be attenuated by means of a wavefield decomposition (WDC) into up and downgoing wavefields. We apply an elastic decomposition scheme to earthquake recordings in the Tyrrhenian Sea to demonstrate the potentials for different passive seismological studies. A three-step decomposition approach has been developed giving optimal results for our earthquake data. Relative amplification factors between hydrophone and seismometer can be constrained during decomposition. In our case, factors in between 0.25 and 0.4 have been found. We show that water-layer multiples on recordings of local deep earthquakes are significantly reduced, so that structural phases in the coda of the P phase can be studied. The seafloor P-wave impedance contrast at two nearby stations is estimated to the orders of 1.3 and 1.5, indicating that the uppermost layer was very muddy and unconsolidated. We demonstrate with synthetic data that teleseismic receiver functions are strongly distorted by means of water-layer multiples. The WDC significantly improves the signal-to-noise ratio of structural phases in receiver functions. A single station application to real data confirms the theoretical predictions. We predict the biasing effect of traveltime residuals as estimated by cross correlation of teleseismic recordings from different stations in the order of up to 8 s at waves with a dominant period of 50 s. Waveform decomposition removes this apparent traveltime residual and enables unbiased estimates. The theoretical predictions are verified with real data from two teleseismic earthquakes. Based on our results we strongly recommend applying an elastic WDC to passive seismological recordings on broad-band stations.

@article{thorwart_dahm:2005, abstract = {Seismic data from ocean bottom stations show strong water-layer multiples on the hydrophone and seismometer channels depending on the water depth and the seafloor impedance contrast. These multiples can be attenuated by means of a wavefield decomposition (WDC) into up and downgoing wavefields. We apply an elastic decomposition scheme to earthquake recordings in the Tyrrhenian Sea to demonstrate the potentials for different passive seismological studies. A three-step decomposition approach has been developed giving optimal results for our earthquake data. Relative amplification factors between hydrophone and seismometer can be constrained during decomposition. In our case, factors in between 0.25 and 0.4 have been found. We show that water-layer multiples on recordings of local deep earthquakes are significantly reduced, so that structural phases in the coda of the P phase can be studied. The seafloor P-wave impedance contrast at two nearby stations is estimated to the orders of 1.3 and 1.5, indicating that the uppermost layer was very muddy and unconsolidated. We demonstrate with synthetic data that teleseismic receiver functions are strongly distorted by means of water-layer multiples. The WDC significantly improves the signal-to-noise ratio of structural phases in receiver functions. A single station application to real data confirms the theoretical predictions. We predict the biasing effect of traveltime residuals as estimated by cross correlation of teleseismic recordings from different stations in the order of up to 8 s at waves with a dominant period of 50 s. Waveform decomposition removes this apparent traveltime residual and enables unbiased estimates. The theoretical predictions are verified with real data from two teleseismic earthquakes. Based on our results we strongly recommend applying an elastic WDC to passive seismological recordings on broad-band stations.}, added-at = {2012-09-01T13:08:21.000+0200}, address = {Institut fr Geowissenschaften, Christian-Albrechts-Universitt zu Kiel, 24118 Kiel, Germany. E-mail: thorwart@geophysik.uni-kiel.de; Institut fr Geophysik, Universitt Hamburg, 20146 Hamburg, Germany}, author = {Thorwart, M. and Dahm, T.}, biburl = {https://www.bibsonomy.org/bibtex/22049155ca1bad40794c727b4646871e5/nilsma}, doi = {10.1111/j.1365-246X.2005.02761.x}, interhash = {7124284ae7909cff8273bbe52f96f807}, intrahash = {2049155ca1bad40794c727b4646871e5}, issn = {1365-246X}, journal = {Geophysical Journal International}, keywords = {geophysics seismology}, month = nov, number = 2, pages = {611--621}, publisher = {Blackwell Publishing}, timestamp = {2021-02-09T13:23:47.000+0100}, title = {Wavefield decomposition for passive ocean bottom seismological data}, url = {http://dx.doi.org/10.1111/j.1365-246X.2005.02761.x}, volume = 163, year = 2005 }